HPL memorial

HPL memorial

In memory of Hans Petter Langtangen

1962-2016

Hans Petter Langtangen, Simula, August 2012.

We are very sad to inform you that our friend and colleague, Professor Hans Petter Langtangen, passed away on October 10th.  Hans Petter was an extraordinarily productive author, lecturer, supervisor and researcher. His books on software and methods for solving differential equations are widely used and have influenced these fields considerably. He established one of the most popular enduring courses at the University of Oslo and supervised nearly 100 MSc or PhD graduates.  Scientifically, he was always concerned with the efficient solution of differential equations, in terms of both CPU and human efforts. He produced scientific software of extremely high quality that has found users all over the world. Hans Petter was also leader of a Norwegian Center of Excellence. The scientific computing community also knows him as a long time member of the editorial board of SISC, and, in particular, as the Editor-in-Chief from 2011 to 2015.

Hans Petter loved his work and intensified his efforts after becoming ill. He concentrated on his books, and finished the last book only one week before he died. During his period of illness, he impressed both friends and colleagues by notable openess about his disease, regularly updating a Facebook group with information about the development of the cancer and his treatment.

Hans Petter was an unusually friendly man, always willing to share whatever knowledge he had with others. His impact on students and colleagues has been enormous; no one left his office or his auditorium without deeper insight, and a feeling of joy.

Hans Petter will be deeply missed by his family, friends and by colleagues from all over the world.

Aslak Tveito, CEO Simula Research Laboratory from 2002 to 2022

Morten Dæhlen, Dean, The Faculty of Mathematics and Natural Sciences, University of Oslo from 2013 to 2020

We invite you to share your memories of Hans Petter.

Memorial guestbook

There are 109 entries found in this memorial guestbook. The guestbook is now closed for new entries.

Yufeng Wang wrote on November 8, 2023 at 3:23 pm

I am searching for some teaching material for my course on computational geophysics which involves PDE numerical solvers and scientific computing. Prof. Hans Petter's books and website are awesome and really helpful!

Carlos Pena from Managua wrote on December 10, 2022 at 4:25 pm

El Profesor Hans Petter escribio uno de los libros mas gratificantes sobre Programacion en Python, es una lastima que se haya ido tan pronto.

Paige from Boulder, CO wrote on September 23, 2022 at 7:09 pm

Dr. Langtangen's textbooks and free learning resources have become indispensable to my thesis research and I was truly saddended to learn of his passing. I sincerely appreciate his easy-to-understand writing style and deep commitment to open source material. While skimming through some of the entries in the guest book, I learned about how caring, kind, and funny he was, in addition to being a brilliant mind. I have recommended his work to many people over the past couple of years, and I hope that it brings those who loved him comfort to know that HPL is *still* mentoring young researchers and assisting them in understanding these dense topics.

Pavan Inguva from Cambridge, Massachusetts wrote on November 1, 2021 at 5:03 pm

I was developing my own course material for numerical methods using Python and came across the wonderful work done by Prof Hans Petter. His insight and easy-to-understand writing style is truly remarkable. I am grateful for the good work he has done.

Amin from Vancouver, Canada wrote on October 12, 2021 at 4:29 am

I was searching for the fundamental course in computational engineering to solve some biodegradation problems for my thesis and found many of Peter's books related to this field. His effort really inspires me. RIP great teacher

Mugambi Ndwiga from Nairobi, Kenya wrote on July 29, 2021 at 5:51 pm

I was stuck trying to find a way to discretize and implement a numerical solution for a wave equation. I found a very good explanation and a python implementation that I adapted for my solution. On checking more about the person behind the work, I was very sad to find out that he had passed away. May you rest in peace sir.

Angela Rizzi from Göttingen wrote on November 15, 2020 at 3:46 pm

Today I was working out the solution of a PDE by following the concepts by Prof. Langtangen. I found a tiny inconsistency within the text and I formulated following Email to let him know about a possible errata. My Email started with: "Dear Prof. Langtangen, First of all let me express my huge appreciation for your contributions in GitHub and in your books on the topics of scientific computations. Great work! It is my personal guide for computer simulations and extremely useful for education, but not only. Thanks! ... " After looking for his Email address, I came to this page. How sad to red about his passing away. His excellent work will remain!

Kaid Noureddine from Algeria wrote on October 30, 2020 at 1:31 pm

We really miss you Hans Petter, all what I have learned concerning differential equations and Python programming was from you (Git Hub). "If a son of Adam dies, he ceases his work except from three: an ongoing charity, a knowledge that can be used, or a good child who is invited"

Magnus Bjørnsen Løbeg from Bergen wrote on December 3, 2019 at 3:38 pm

I started master studies at Physics of Geological Processes in 2007 because HPL was working there. When I started he had moved to another job, but he was my external sensor for my master dissertation. It was a short and intense meeting with this lovely man. Thank you som much. Kind regards Magnus

ZHANG, Chunyuan from Changsha, Hunan, China wrote on October 6, 2019 at 11:24 am

I met him in UiO in 2014 and have used his Python textbook since 2015. He gave me all the resources of the course. The textbook have been translated to Chinese this year and will be published soon.

Jose Funes from Washington, DC wrote on October 5, 2019 at 2:56 pm

Sad news, I met him by reading his excellent books in Python, just a brillian mind! to spread knowledge to the world. I was shocked to learn that he passed away. My sincere condolences to his family.

Steffen Loen Sunde from Trondheim wrote on August 17, 2019 at 10:32 am

Saddened to see such a great person passing away. I did not have the chance to meet Hans Petter in person, but his work is a true source of inspiration. My most sincere condolences to his family, friends and colleagues.

Arben Tapia from Toronto wrote on April 8, 2019 at 7:17 pm

I wish to express my deepest condolences for Prof. Hans Peter family, friends and ex-coworkers. While using some of Prof. Hans Peters' ideas in the classroom, I just sadly learned about the passing away. It's no exaggeration to say I feel like I have lost a personal friend and mentor even though I never met Prof. Hans Peter. Sincerely, Arben Tapia

Raffaele Ponzini from Rodero wrote on March 16, 2019 at 9:18 am

If I'm using Python for my technical applications is because I had access to the books written by Professor Langtangen. His work remains in my mind as one of the clearer examples of what teaching and explaining something to other people should be. I never had the chance to thank him in person. I will really miss his contribution to science. Sincerely, lele

Olav D. Snørteland from Stavanger wrote on February 5, 2019 at 10:25 pm

Wow, I was really sad to hear that this great guy had passed away. Met him fresh out of high school teaching us about python at UiO in 2009. By far, the best lecturer I have had the last 10 years.

Siddhartha Ommi from Nantes wrote on January 3, 2019 at 2:01 pm

I have recently started using FEniCS and reading his books. I love the elegance in which he describes the use of each line in the Python script. I googled his name to find his email to ask a few questions and I came to know that he is no more. RIP Hans Petter.

Peter Carmicahel from Sunnyvale wrote on November 22, 2018 at 12:23 am

I am so deeply saddened to hear that Hans Petter has passed away. I'm reading his works, currently, and they are deeply satisfying, in a way that very few books are. They are deeply helpful too, in a way that even fewer books are. And now I've learned that this great man, who wrote and is teaching me still, has passed away. My profoundest sympathies to those of you who knew him well.

Phi Ha from Berlin wrote on November 14, 2018 at 7:22 am

Even though I have never had a chance to meet/work with prof. Langtangen, I really admire him for his research/teaching career. In fact, since reading his Python books, I have found love in numerical mathematics. I could not express how elegant the book is, and how it have such a strong impress on a theoretical mathematician like me. So thank you very very much and rest in peace, prof. Langtangen.

Aarish Shaheen from New Delhi wrote on September 17, 2018 at 8:37 pm

What can I say? I learnt the ropes of computing from his excellent python book. Thoughts and prayers fir his family.

Panos the Greek from Bologna, Italy wrote on January 22, 2018 at 9:21 pm

Dear Hans, I googled your name to find your email address because I wanted to say "thank you", even if never met you, for helping me using Python and Flask to build my scientific applications on the web. Nobody has explained better to me what purpose all those commands serve. I was delighted one night finding your notes "Using Flask for Scientific Web Applications" on the web. Your clear writing style was very much appreciated. Then, I was taken aback by the sad news that I found. I am very sorry that sometimes people like you have a short life. I send my condolences to your best friends and family.

Ajay Rawat from Chennai wrote on October 21, 2017 at 5:51 pm

I was pulled towards scientific computing using Python by reading his books and softwares. Truly a great soul and his departure is a tremendous loss to scientific computing community. May his soul rest in peace.

Daniel Mejía R. from Medellín(Colombia) wrote on September 28, 2017 at 2:12 am

A great loss for science. I never met Hans Petter L. in person, and only means of knowing him was through his books and source code works such as DiffPack and Doconce. A great scientist concerned with education and the availability of good study materials and software tools, I'm sure his legacy will continue making echo as generations pass.

Klaus G. Müller from Wassenaar (Netherlands) wrote on September 2, 2017 at 3:38 am

It is only today that I learned of Petter's death, and I am so shocked and sorry. Petter's books on scientific software for the first time comprehensively showed what a scientist should and could do with Python. Before his books, Python was just another nice language. He effectively showed the direction in which NumPy should be going. My personal experience with Petter have been a few most productive exchanges by e-mail during my development of SimPy. I never realized how young he was, his breadth and depth in his work suggested to me that I was dealing with a quite senior scientist. I am missing him, and I will now sit down and read his books from front to cover again, with a lump in my throat. RIP, Petter, and thank you for your wisdom!

Shubeur Rahman from Abu Dhabi wrote on April 13, 2017 at 2:49 pm

No memorial tribute over a few paragraphs will be adequate to thank Hans Petter for his contribution to the education, career, and life of mine and no doubt countless others, but I nevertheless feel that I should try to write a few words out of respect. I met Hans Petter back in 2002 during the early stages of my PhD research at Cambridge and when I was much in need of inspiration and guidance. I emailed him about a technical problem, and to my surprise he responded quickly and invited me to spend a month in Oslo working with himself and his team. This I believe to be the turning point of my career and my life as Hans Petter soon became my mentor, and friend throughout various challenges I had in my life since then. The words “never give up” Hans Petter once used still continue to echo in my mind. I recall his modest self-introduction when we first met, and then showing me around the lab introducing me to the Simula team, then driving me to the train station at the end of the day. We kept in touch over the years writing regularly by email. In October last year (2016) when I wrote to him, he replied as promptly as ever and he mentioned that he was unwell although not giving details. I replied with the words “never give up”. Little did I know that he was to pass away only a few days later. Hans Petter was an incredible intellect and person and I was very fortunate to have him play a huge part in my life. My thoughts are with his family, friends and colleagues and all the lives he touched.

Murilo Henrique Moreira from São Carlos wrote on February 15, 2017 at 2:30 pm

I'm a Brazilian student of Materials Engineering, I did not have the opportunity to have great teachers on my graduation, but I really want to work with numerical simulations. I have a lot to learn yet, but work from people who REALLY cares about the idea of sharing knowledge with others do inspire and make it possible that one day people like me, with not the best basis, are capable of dreaming of one day become skilled scientists like Professor Hans Petter. I didn`t even started to read all his works, I`m in the second week of my internship (which involves directly numerical simulations), but I truly believe that this book may help me. It is beautiful to live in a world were people like Professor Hans Petter exist. I am thankful for him without even knowing him, without even understanding the size of his knowledge nor the importance of such subjects, but I think that this is the mark of people like him. Legends will never die, it is a true statement. In live and in death, he still help us, and this is brilliant.

Bjørn Remseth from Heggedal wrote on February 8, 2017 at 6:42 am

Many years ago when I worked as a sysadmin for the Math department at the University of Oslo, Hans Petter was a dear colleague. His keen interest in bringing the very best computing resources to the students was an inspiration, and it was always fun to talk with him about any subject. He was a man of many talents, I remember being very surprised when on one "Eplefest", the student/faculty Christmas he played guitar in the band. He played very well btw. I only heard about his death today, and I was immediately saddened by it. He was a great guy.

Alvaro Coutinho from Rio de Janeiro wrote on December 1, 2016 at 5:09 pm

I first met Hans Peter at SIAM Geosciences meeting in early 90's. At that time we were doing porous media flow with stabilized finite element methods. Since them we continued to follow his many contributions in this area, always creative and deeply rooted. May he rest in peace.

Michael Thuné from Uppsala, Sweden wrote on November 28, 2016 at 4:17 pm

During the late 1990s and early 2000s, Hans Petter was a frequent guest at the Division of Scientific Computing within the Department of Information Technology at Uppsala University. The primary contact point was with our group on software tools for high-performance computing, where we benefitted greatly from Hans Petter's expertise in that area. However, with his broad competence in all aspects of Scientific Computing, Hans Petter become an appreciated discussion partner for people from all parts of the division. For many of us, Hans Petter also became a personal friend, kind-hearted and brilliant. We miss him deeply.

Simen Kvaal from Oslo wrote on November 16, 2016 at 8:35 pm

I met Hans Petter as a young student in 2001 (I think it was), attending his numerical methods for partial differential equations course at UiO. He led me onto my scientific path with that course. His glowing enthusiasm was catching, and his warm personality was unique, always supportive and inspiring self-confidence in all the students. I always looked forwards to the occasions I had to see him over the years, and that I will deeply miss.

Jacek Starzyński from Warszawa, Poland wrote on November 8, 2016 at 9:53 am

I was heartbroken by this sad news. I knew Hans Petter by email only, but we started our contacts in 1994 on the occasion of the first Diffpack release. He was a brilliant mind, full of ideas and always humble and keen to help. He passed away, but his memory will live among us.

Temsgen Abraham from Kløfta wrote on November 2, 2016 at 3:47 pm

While I did not have the honour to work under Professor Hans Petter Langtangen, I did take some of his courses at UiO. I remember him as a brilliant teacher and a very humble human being. Reading all these letters from people all around the world shows the profound impact Professor Langtangen had on everyone he met. RIP hpl.

Xiyang from Trondheim wrote on November 2, 2016 at 2:45 pm

To Professor Petter, I never see you before in my real life, but I am learning FEniCS from the beginning of my PhD life. Your influence on me is fundamental and indescribable. Miss you......

Jonas Lindemann from Skurup wrote on October 31, 2016 at 9:50 pm

Hans Petter was my opponent at my PhD Defense. I remember being extremely nervous as I new his reputation in the field. Hans was a great opponent and it was a very good discussion. After the defense, which very C++ focused, he asked my why don't you use Python instead. This opened my eyes to a new programming paradigm, which I have continued to develop. You will be missed.

Peder A. Tyvand from Ås wrote on October 25, 2016 at 12:45 pm

The first time I heard of Hans Petter when I was a post.doc. at MIT in 1984. The rumour of his brilliance had spread across the ocean already when he was young student! Those of us educated at the mechanics group are deeply honored that he spent his young years with us. I went to many seminars to meet him, even though I had left the department just at the time when he started his master work there. He was a fantastic person in every sense.. Always open, continuously spreading ideas and inspiration around him. Academia is a good place to be, once we find people like Hans Petter to be around. His personality was a rare gem, uniquely blending generosity with brilliance. He is deeply missed, but we find continuous inspiration in our memories of him.

Ilmar Wilbers from Oslo wrote on October 23, 2016 at 11:27 am

As so many others, Hans Petter heavily influenced the direction my studies would take. He taught me Python and soon became my supervisor for my MS. But I was also fortunate enough to work very closely together with Hans Petter for a full year, assisting him with creating the "Introduction to programming with scientific applications" course at UiO. He was a remarkable person, RIP HPL!

Ralph Lorentzen from Fornebu wrote on October 19, 2016 at 5:51 pm

When several years ago I as a retired scientist asked if I might work as a volunteer at Simula, I was interviewed by Hans Petter and Are Magnus. It was a pleasant experience which resulted in the startup of an interesting and challenging project. The project resulted in a new approach for carrying out computer experiments, and Hans Petter guided me gently throughout the project. I am deeply grateful for that.

Trond Vidar Stensby from Oslo wrote on October 19, 2016 at 2:16 pm

I first met Hans Petter while doing my master degree at SINTEF Applied Mathematics. His enthusiastic promotion for using object-oriented techniques for numerical software development sparked my interest for the C++ programming language. He was an excellent motivator and I am grateful for the influence that Hans Petter's teachings has had on my entire working life. Rest in peace, Hans Petter.

Stuart Clark from Oslo wrote on October 19, 2016 at 8:41 am

Hans Petter was a great inspiration to me. I will miss his drive and positive attitude to science. May God give comfort to his family at this difficult time.

Helge K. Dahle from Bergen wrote on October 19, 2016 at 6:14 am

I was very sad to learn that Hans Petter died. Hans Petter was a great scientist and a warm and good person. He will be deeply missed by the Norwegian scientific community.

Arnoldo Frigessi from Oslo wrote on October 18, 2016 at 8:56 pm

Hans Petter was open and clear, friendly and determined. Open to discuss themes that others were interested in and found important, beyond his own interest, to learn and understand and contribute. Clear in his opinions, with deep arguments and well documented, precise in his polite way. Friendly, with a biiig smile, gentle eyes under his glasses, yes in a hurry, like we all are, but you felt he saw you and heard you. Determined where you needed to be so, because there are principles, maybe ideals, that matter. He did not like methods that find an occasional application in biology or medicine, he wanted to start with the life-science question and develop the mathematical and digital instruments to answer them. We thought we could start to do multiscale models and statistical inference together, we hoped so. There was no time, Hans Petter. But we shall try to do it and we know you would have liked it.

Kristin Vinje from Oslo wrote on October 18, 2016 at 7:23 pm

As former employee at Simula I had the pleasure to work closely with Hans Petter for several years. I first learned to know Hans Petter as a fellow student back in the early eighties at the University of Oslo, although he quickly advanced to teaching as we still finished up our degree. Hans Petter was remarkable in more than one way; he was an optimistic and creative soul, a very friendly and helpful person, a genius researcher and an excellent teacher. Until recently he also supervised two of our sons at UiO, and they can confirm what a brilliant and enthusiastic teacher he was! On behalf of my family and myself I will express my deepest condolences. RIP, Hans Petter!

Gerhard A. Holzapfel from Trondheim and Graz wrote on October 18, 2016 at 4:42 pm

Hans Petter passed away far too early. He was a very special person equipped with the talent to reduce complexity of numerical programming in order to pass it over to students in simple words and in form of enjoyable books on scientific computing. He had the ability to interact with many different people, he was very inspiring, positive, enthusiastic and friendly. Hans Petter was a generous person full of energy, spirit, passion and love. The world needs more people like him. As a perfect model of success combing work with life he will remain in our minds and continue to be present.

Helge Holden from Trondheim wrote on October 18, 2016 at 3:54 pm

It is so sad. It is a great honor to have known Hans Petter.

Johan Jansson from Stockholm wrote on October 18, 2016 at 3:46 pm

I was very sorry to hear the news. I first met Hans Petter over 10 years ago, just as the FEniCS project was starting. His encouragement and energy will always be an inspiration to us all. He was a voice of reason and a visionary, and his work will live on.

Johannes Ring from Oslo wrote on October 18, 2016 at 2:43 pm

I first met Hans Petter as a student back in 2003 at the University of Oslo. He immediately became my favorite teacher with his enthusiastic and inspiring lectures. I feel very fortunate and privileged to have had him as my supervisor in my master degree study. Not only was he extremely encouraging and helpful, he was also very kind and understanding. Later he gave me the opportunity to work at Simula, a job which I have enjoyed for the past nine years. I have so much to thank Hans Petter for. I will miss him deeply.

Susanne Støle-Hentschel from Oslo wrote on October 18, 2016 at 1:37 pm

Hans Petter gave me the opportunity to start working at Simula through a summer job and like many others I ended up at Simula for some time. During this period, I first got in touch with research and I felt at home immediately. I will always be grateful for this experience. I remember Hans Petter as many others have described already. I would like to share two memories that show his humbleness. I was always amazed how he could remember details of my project event though it was only one small thing that he did in addition of million others. Once, after a summer party and some beers he explained the downside of is memory. He kept on remembering details about people and situations that he would rather forget. It felt like he wanted to downscale his size. Many years later we were talking at the "eplefest". I expressed my gratitude for his modernization of teaching at UiO and that I often was pointed to one of his books about python when I tried to find a solution to something on the internet. His response was typical HPL style, something like " Oh that happens to me a lot too, and it annoys me, because I know what I am looking for cannot be found there"

Chandrika Kamath from Livermore wrote on October 18, 2016 at 3:24 am

I regrettably did not have the good fortune to know or work with Professor Langtangen. However, I learned about object-oriented software development from his work on Diffpack, which, along with his book on Python for Computational Science, have greatly influenced the software I have developed for data analysis. I very much appreciate his willingness to make his expertise so easily accessible to all. May he rest in peace.

Xing Cai from Rykkinn wrote on October 17, 2016 at 11:35 pm

Hans Petter was a perfect example of "Once a teacher, always a teacher". In 1992, I was very fortunate to become one of his numerous master-degree students. In 1995, when I embarked on my PhD, I was again privileged to have Hans Petter as one of my doctor-degree supervisors. Thankfully, Hans Petter's supervisor role never actually ceased at the completion of his students' academic degrees. He continued to nourish me in science as well as in life's other aspects, ever since. Without exaggeration, I can say that Hans Petter left his marks on every progress in my career. It thus pains me excruciatingly to realize that I have lost my life-time mentor, forever. "I'm eternally in debt to you, my dear teacher!"

Shewli Biswas from Kolkata wrote on October 17, 2016 at 1:43 pm

I am deeply shocked and saddened by the passing away of one of the great geniuses in bringing the complexities of numerical programming and bionumerics near to ordinary students like me. I am greatly indebted to Professor Langtangen's work. May he rest in peace and remembered for eternity.

Thanh-Ha Le Thi from Heidelberg wrote on October 17, 2016 at 1:13 pm

I have been very fortunate to know Hans Petter as author of Springer when I joined Martin Peters’ Mathematics and CSE Editorial at Springer in 1998. Since then, I have handled numerous books written and edited by Hans Petter, among them, the bestseller TCSE 6 “A Primer on Scientific Computing with Python”, now in its 5th edition. Hans Petter was very enthusiastic about his new book projects and could often not wait to get his hands on a printed copy of his “new baby”, Hans Petter’s own words of his newly published book. During the production process, Hans Petter’s feedback was very speedy and constructive. I am so sad to lose our very special and endearing author and will deeply miss our regular email contacts.

Magne Jørgensen from Strømmen wrote on October 17, 2016 at 1:08 pm

I will remember Hans Petter. I'v discussed research and life in general with Hans Petter on many occasions and look back at those discussions as some of the best I ever had. He has inspired me in teaching, research and how to deal with difficult life events. Grateful to have known Hans Petter.

Svein Linge from Porsgrunn wrote on October 17, 2016 at 11:29 am

Dear Hans Petter, “Very often in life, and in computer programs, the next action depends on the outcome of a question starting with “if”.” Well into your cancer treatment, you wrote this as the opening line of chapter 2 in a recent book of ours. That line will never be forgotten Hans Petter... Neither will I forget all the positive, enlightening and motivating moments you provided. A mountain of impossibilities was nowhere to be seen after a chat with you! Not too long ago, in the afternoon of August 19th, we met in your apartment to play some guitar and discuss book issues. We had to meet in the evening, since you were all day in the hospital. Coming home, you stepped out of the car with a smile, walked the stairs very determined (but with a rest or two) and went directly to your guitar room. You were too weak to bend down and plug in all the cables, so you directed me how to do it. The following 1-2 hours of non-stop playing will always remain a treasured memory for me. After playing, you were really exhausted and I had to lift you up on your feet... We got over to the living room and you sat down started talking about the book issues we had on the agenda. Clearly, you had no intentions about ending our evening! I was the one who had to suggest we better stop, which I did a bit later, having watched you trying to fight your closing eyes. Your determination was nothing less than outstanding. I am grateful for the time we had together Hans Petter. Thanks for everything. Svein Linge

Randy LeVeque from Seattle wrote on October 17, 2016 at 1:46 am

Hans Petter was an inspiration to us all. His books and other teaching materials have been highly influential, not only to countless students but also to a broad range of researchers in computational science, across many fields. Thanks to Hans Petter, my wife Loyce and I had the opportunity to spend a couple months at Simula on sabbatical in 2012, and the great pleasure of getting to know him better, and to appreciate what a warm and generous human being he was in addition to his scientific talents. We will miss him.

P.A Fronth Nyhus from Oslo wrote on October 17, 2016 at 12:04 am

My first brief encounter with you HP dates back to lower secondary school, a small gig/rehearsal at your parent’s house. You had already then a natural and built a positive reputation for being extraordinarily good with numbers math and indeed people who had a hard time to grasp it . A talent which you made the most and you into a brilliant scholar. I always knew whom to turn to in such matters and you were always open and eager to assist and provide clues where to go next in finding possible solutions and to test the solution/ problem at hand. Beyond QED , you used your curiousity as to provide a deeper insights and a deeper understanding. Whether it be HMM, NN, how to go about a set of ODE , PDEs , DD and ML and get the most out of precious CPU time or just simply in meeting people in a fair and square manner. You always seemed to have or made time, when we from time to time met albeit to infrequent. Open minded, reflexive and keen to help and even if I did not get it the first time around, I always had this good feeling, good vibrations ,and encouraged to pursue matters further. You will be sorely missed HP and I for one will always remember our first brief encounter and you as playful Mathemusician. An extraordinary gifted yet ordinary guy I feel proud to have known. RIP HPL my guitar gently weeps.I really whish you where here ,but I take comfort in that all the great work you done will not be forgotten.

Stefan Turek from Dortmund wrote on October 16, 2016 at 9:28 pm

I was very very sad to hear that my long time colleague and also friend Hans Petter, who was my partner since the 90s in many discussions, projects and conferences regarding mathematical software (for PDEs based on FEM and particularly for flow problems) und HPC techniques, has already passed away, much too early. I will never forget you!

Galen Gisler from Los Alamos, NM, USA wrote on October 16, 2016 at 8:43 pm

I wish I could have known him better, and for longer. I met him for the first time when I moved to Norway in 2006 to join the Centre for the Physics of Geological Processes. An affiliate of the Centre, Hans Petter surprised me by saying he was excited to meet me; said he knew of my numerical work on asteroid impacts! That embarrassed me. I didn’t think the work was good enough to warrant his attention. Our contacts during my years in Oslo were always pleasant but unfortunately infrequent. A his invitation I gave a talk at Simula. He introduced me by praising my work most highly, and then bringing me back to earth by saying that I was just a regular guy after all. It was fun, true, and totally disarming. He was also a “regular guy”,.easy to talk to, friendly and helpful The last time I saw him he was playing guitar in a little rock band assembled for the Mathematics Institute’s “Eplefest” in January 2015, lively and energetic as always, expressing the same enthusiasm in his music as in everything else. I will certainly miss you, Hans Petter!

Åsmund Ødegård from Ås wrote on October 16, 2016 at 8:31 pm

Hans Petter, you was a very special person. On one side, a brilliant scholar and professor with deep knowledge in your fields, as described by many here. But on the other side, also playful and with the enthusiasm usually associated with a child - open to new ideas, eager and spontaneous. I met you in the mid 90's, and learnt to "speak" C++ from you. Later, you was in particularly instrumental in the last phase of my phd. But even more dear to me, and something I will keep in my memory for the rest of my life, are the many exciting and wonderful discussions we had - about scientific computing, and almost all other sorts of technological topics, as well as music and life it self. I will miss you dearly HPL, but what I learnt from you will continue to influence my life and work for the years to come.

Erlend Arge from Oslo wrote on October 16, 2016 at 6:20 pm

Hans Petter was a visionary. Singularly bright. Unbelievably productive. Confident, but open and humble. A lecturer and a listener. He had this rare ability to bring out the best in people. When we talked, he always made me feel I had something to offer. Hans Petter was a scientist and also a musician. A common friend meant he could step in as lead guitarist in any rock band whenever he liked. I knew Hans Petter for 30 years. We worked together in various contexts after we met as students in the 1980’s. Our last project was our joint sax and guitar solo on Van Halen’s “Jump” at Simula’s Christmas party in 2012. Hans Petter was intense! A precious memory. I am grateful to have known him.

Omar Ghattas from Austin, Texas wrote on October 16, 2016 at 10:23 am

I first interacted with Hans Petter many years ago. I had asked him to review a full manuscript for a proposed book. Knowing how difficult it is to find people willing to review full manuscripts, I was expecting a brief, high level review. Instead, I received a remarkably thorough and detailed review, with constructive recommendations on just about every section. I was to learn that this was typical of Hans Petter: always going far beyond the call of duty in his commitment to and support of the field of CS&E. How tragic it is that HP has been taken away from the CS&E community--not to mention his family, friends, and colleagues--at such a young age. But as anyone who interacted with him knows, his enormous legacy as a tireless researcher, author, advocate, editor, mentor, teacher, and colleague will continue to influence so many for years to come.

Adnan Rauf from Sukkur, Pakistan wrote on October 16, 2016 at 3:19 am

Thanks HPL for enabling High Performance Learning Thanks for Opening Up new worlds We are grateful

Stein Christian Waage from Oslo wrote on October 15, 2016 at 10:33 pm

I have known Hans Petter since we both went to the same high school. We have remained very good friends ever since. Hans Petter was always excellent in all that he did. He was brilliant at school , he played several instruments (all his friends will remember his late night guitar sessions), he had a lot of energy and we all enjoyed his company. Hans Petter you were a true friend and my kids and my wife will miss you dearly. Rest in peace my friend we will never forget you.

Abdullah Alhadab from Thuwal, Kingdom of Saudi Arabia wrote on October 15, 2016 at 6:33 pm

Currently, I am a master student at king Abdullah of science and technology KAUST. I have never met Hans, but I learned so much from his books, After reading Python Scripting for Computational Science and A Primer on Scientific Programming with Python. I fell in love with numerical solution of PDEs and ODEs and python as programing language. I read most of the book on Hans website. I am really amazed by his diligent work, productivity. Because of his books and clear explanation I started thinking to join Simula Research Laboratory to do my PhD straight after I finish my Msc degree. It is a great loss to the scientific community. May God bless his soul

Andreas Kloeckner from Champaign, IL wrote on October 15, 2016 at 5:39 pm

I met Hans Petter through a SIAM CSE conference in Miami in 2009. Being at the conference (my first!) was a bit terrifying, and I remember how Hans Petter as an organizer of the session in which I was speaking radiated kind calmness, encouragement, and enthusiasm. I left Miami with a very positive impression of the CSE community, and that was in no small part thanks to him. A later visit to Simula in 2011 underscored how his leadership had helped create a fantastic environment there for scientific computing research. The discipline (and scientific computing in Python specifically) is poorer for having lost him.

Jan Høiberg wrote on October 15, 2016 at 4:26 pm

Dette er en svært trist dag for alle oss som lærte Hans Petter å kjenne. Han var et unikum på alle måter, og vil bli dypt savnet. Hvil i fred, HP.

Leif Rune Hellevik from Trondheim wrote on October 15, 2016 at 1:51 pm

Ever since I meet Hans Petter for the first time, when he acted as my opponent at my PhD-defense in 1999 and later on as a collaborator at CBC, I have learnt to know him as an enthusiastic and playful scholar with a great passion for science. He was truly a unique character in our field which as been mentioned by many others. Who else write their own flexible markup language producing output to a range of web-formats and PDF, before setting off to produce piles of textbooks. But maybe more important was his energetic and natural ways of interaction with friends, colleagues, collaborators of all kinds, which inspired so many. I will miss him dearly both as a friend and collaborator.

Truls Flatberg from Trondheim wrote on October 14, 2016 at 5:49 pm

I was shocked and saddened by the passing of Hans Petter. I spent an intense autumn with him back in 96 as he was supervising my diploma thesis at NTNU. He was one of the few academics I know that also took in students from othe universities. I think this was a result both of his curiosity and willingness to collaborate. We spent several months trying to get some grasp of control theory and pdes without Michael success. Still he kept up his optimism making me never doubt as well. Two weeks before the deadline we has a breakthrough and the thesis was completed. I met up with Hans Petter a few years later and he admitted that he had never been so nervous on the behalf of a student. I still look back to that period with fond memories and will sorely miss the opportunity to discuss mathematics or the pleasures of the sauna with him.

Joakim Sundnes from Oslo wrote on October 14, 2016 at 2:25 pm

Very few people have impacted my life as much as Hans Petter. I first met him when he was teaching mechanics at UiO in the mid 1990s. I was an undergrad with only a vague plan for my studies, and Hans Petter's enthusiastic and insightful lectures effectively decided my path. Years later we became colleagues at Simula, and he continued to impress and inspire me. I will miss him dearly.

Espen H. Kristensen from OSLO wrote on October 14, 2016 at 1:37 pm

To the professor that got me interested in studying mathematics and informatics, sparked my interest and turned it into a glowing fire. The man behind a course and a way of thinking about science education in a more modern context, who found a brilliant way to both teach valuable informatics skills needed in the sciences and to use the same education as a pedagogical tool to learn in other science subjects. Programming is a wonderful, wonderful thing, and you helped me see that. To the person that influenced me the most without us being personally acquainted, I thank you and am very sorry to see you go a long time before you should have. We lost one of the greats on Monday. My condolences to your family and loved ones.

Tor wrote on October 14, 2016 at 1:29 pm

Så utrolig trist. Husker han som en av favorittforeleserene mine.

Ola Skavhaug from Oslo wrote on October 14, 2016 at 12:31 pm

Visiting Hans Petter in his office to discuss numerical software development was always a delight. With his great presence, enthusiasm, knowledge, and inventive mind, you left the room feeling a little wiser and happier. I will dearly miss Hans Petter, and continue to take joy working in a field greatly influenced by his visions.

Ginevra Testa from Oslo, Norway wrote on October 14, 2016 at 12:31 pm

Hans Petter was my professor since 2011 in a number or scientific programming courses, and he surely made an impact on my life. There are few professors who are genuinely enthusiastic about their field, about teaching to young students and as well making a greater contribution to science as Hans Petter was. He truly believed in his students and mentored us in a wonderfully human, empathic way, without prejudices. His lectures, books and publications were powerful, inspiring and elegant. He has set a noble standard for teaching and doing research.

Halvard Moe from Kolsås wrote on October 14, 2016 at 11:41 am

I first met Hans Petter in 1987 during my second semester at University of Oslo where he was the lecturer of the introductory course in Mechanics, the infamous ME101. Hans Petter’s brilliant and engaged way of conveying the curriculum was very inspiring for a young and undecided student. Also on the social side at the mechanics section of Department of Mathematics Hans Petter was in front bridging the gap between the established professors and the novice students. For me this was pivotal for choosing study - mechanics it was. Later I have had the pleasure of being a colleague of Hans Petter both at the University and at Simula. His determination and engagement never stopped impressing me. Hans Petter will be deeply missed but his legacy will live on.

Yapi Donatien Achou from Oslo wrote on October 14, 2016 at 10:49 am

Hans Petter was a mentor to me, encouraging me in hard time, and seeing the hidden potentials in me. He was friendly, and enthusiastic about every thing. His scientific achievements are well known, but above all, what distinguished him from many was his ability to connect with every one. As a teacher, he was creative, innovative and his goal was to introduce the industry best practices in the class room. He valued the feedback of his students and acknowledge them as an important part of the teaching process. My impression of him was that teaching was a creative and innovative process above all. He surely made a very big impression on me and he will be remembered as a great man. A man of talent. A creative man. A man of heart.

Hoang Xuan Phu from Hanoi, Vietnam wrote on October 14, 2016 at 10:07 am

On 20th February 2005 I invited Hans Petter to give a plenary lecture (http://hpsc.iwr.uni-heidelberg.de/HPSCHanoi2006/invitedlectures.php) at the 3rd International Conference on High Performance Scientific Computing (March 6-10, 2006, Hanoi, Vietnam) and wrote as usual: “We are NOT able to finance travelling expenses of invited speakers.” He replied two days later: “I am happy to accept this invitation. I do not have a complete funding for the travel yet, but I think this will work out.” On 1st November 2011 I invited Hans Petter to join the Editorial Board of Vietnam Journal of Mathematics. He replied two hours later: “I am very happy to accept this nice invitation! Over the years I have quite some experience with journal editing. Right now much of my time is spent on SIAM Journal on Scientific Computing, for which I act as Editor-in-Chief. You should also know that I try hard to come by Hanoi at your conference next spring.” And on 14th April 2012 Hans Petter wrote in addition: “Congratulations with having set all up for the journal! I am proud to have my name on a board with so many famous names.” Just two examples to remember Hans Petter, a very nice and helpful friend, an extraordinarily productive scientist. I will miss him. Our Vietnam Journal of Mathematics will miss him, too.

John F. Burkhart from Oslo wrote on October 14, 2016 at 9:37 am

Ironically, I started reading HPL's books when I came to Norway as a researcher - but did not even realize he was also here. It wasn't until several years later, finding myself a new professor at UiO that I met Hans Petter. My first visit to simula was so inspiring. His openess and willingness to collaborate made an immediate and immense impression. Over the years, I had several further opportunities to work with Hans Petter and some of his colleagues. What became most clear was that, through his enthusiastic and encouraging attitude, he was a force and visionary for those who had the pleasure to interact with him.

Johan Hoffman from Stockholm wrote on October 14, 2016 at 8:54 am

When I think about Hans-Petter I see his warm friendly smile. I first met him in Chicago when he got involved in FEniCS, but long before that I had met his work through Diffpack. I always found him to be visionary, inspiring and constructive in the sometimes challenging landscape of science. He will be greatly missed.

Martin Peters from Heidelberg wrote on October 14, 2016 at 8:27 am

My first meeting with Hans Petter was more than 20 years ago at SINTEF Applied Mathematics. Together with him, Aslak and Are Magnus we explored publication collaborations in CSE. Hans Petter turned out to be an incredible scientist and author. It is unbelievable how fast he could write big books, and how well he did it. I do not know anyone who can do it like he did. Now, after he departed I often think about the fun we had together, like when he was fluently talking in German after having a beer. These memories will stay with me. A friend has left.

Omar al-Khayat from Sandvika wrote on October 14, 2016 at 6:43 am

I first met Hans Petter at the course for high level programming in Python. After that I was hooked on scientific computing and consider myself lucky to mentor under him at Simula. He has had a great impact on my life. As a researcher, he was always a great inspiration and had an ability to see the big picture without being afraid to delve into the gritty details. I will always remember Hans Petter by his good natured demeanor and keen intellect. He will indeed be missed.

Gaute Einevoll from Stabekk wrote on October 13, 2016 at 8:56 pm

While most academics strive to excel in doing what everyone else is doing, the safest road to peer recognition in academia, Hans Petter was a true innovator both in terms of his teaching and his research. Indeed a rare species at Norwegian universities, and he will be sorely missed.

Chris Johnson from Salt Lake City wrote on October 13, 2016 at 5:39 pm

Hans Petter was an amazing scholar, friend and a truly nice, positive, and genuine person. Like Uli Ruede, I first met Hans Petter at the SciTools Workshop 20 years ago. He invited me to give a presentation about our SCIRun problem solving environment. The three of us hit it off immediately and we have been friends ever since. I note that Hans Petter, Uli and I Co-Chaired a Dagstuhl Workshop on Challenges in High Performance Simulations for Science and Engineering back in 2003. Happily, our paths crossed many times over the past 20 years with my visits to Oslo and Hans Petter's visits to Salt Lake City. During his last visit in March 2013 he gave a wonderful Distinguished Lecture (https://vimeo.com/84521038). In looking back in my emails with Hans Petter, there are enthusiastic exchanges about his new books, ideas about Scientific Computing research and teaching, and even about when Norwegian Magnus Carlsen won the World Chess Title. Then in early 2015, I learned the terrible news about his cancer. My father had passed away from pancreatic cancer a few months previously, so I was able to share some of the information I had gathered when trying to help my father fight his cancer. I was very happy to hear how Hans Petter was responding well to his treatments, no doubt in large part because of his very positive attitude. My last long email exchange with Hans Petter was in June when we discussed linking SCIRun 5 (yes, it is still going strong) with FEniCS, so we reconnected on the topic that originally brought us together 20 years ago. I am so very sad Hans Petter has departed. I miss him a great deal. To Hans Petter's family and colleagues, please accept my deepest sympathies and my most sincere condolences .

Kent-Andre Mardal from Oslo wrote on October 13, 2016 at 1:51 pm

It is now almost exactly 20 years since I first met Hans Petter and he told me that I had to learn programming if I wanted to solve PDEs. His course concerning the finite element method (using Diffpack) opened my eyes and swept away my dislike of computers with a shrug. Since then I have collaborated with Hans Petter and enjoyed his enthusiasm, joy for life and work, wise advice, his wide perspective and his warm, including and open mind. I will miss him dearly. He has had such an impact on my life.

Kees Vuik from Delft wrote on October 13, 2016 at 1:03 pm

I have met Hans Peter during several conferences: Computational Geomechanics, SIAM CSE, etc. Furthermore, he was a chief editor of SISC, so I collaborate with him as associate editor. He was a clever and nice person. The CSE community will miss him.

Harish Narayanan from London wrote on October 13, 2016 at 11:46 am

I’m very saddened to hear about Hans Petter’s passing and I am not able to process this news. He was always kind and so very encouraging of my intellectual pursuits. I would be a more timid researcher and individual if not for his encouragement and infectious curiosity. I will miss him.

Bjørn Fredrik Nielsen from Ås wrote on October 13, 2016 at 9:30 am

I learned to know Hans Petter in 1991 as a student at UiO. His lectures convinced me to switch from pure to computational mathematics, and he made me understand the importance of software development for solving contemporary mathematical problems. At UiO, Sintef and Simula his work, smile and laughter inspired all of us. Hans Petter will be deeply missed.

Tor Dokken from Oslo wrote on October 13, 2016 at 8:08 am

In the early 1990s, we had an ambition, in what is now the Department of Applied Mathematics in SINTEF, to build a strong research group in PDE-based simulation. A number of young ambitious researchers address this goal: Hans Petter, Morten and Aslak. Their go-ahead spirit was crowned with success. By the end of the 1990s, Hans Petter was appointed professor at the University of Oslo, and left SINTEF. The foundations of a strong PDE based simulation activity in SINTEF was established, an activity that now near two decades later is still vital and strong. Hans Peter's and my son were playing soccer in different local teams, and when their teams met, we go a chance to catch up watching the game. Later, as a student at the Mathematics Department at the University of Oslo, my son had the pleasure and privilege to have Hans Petter as a lecturer. I believe that his discussion with Hans Petter had strong influence on his choice of master studies, and for the application that resulted in my son's current PhD-position in SIMULA. During his studies, the lectures of Hans Petter were the best, most inspiring and most enthusiastic he attended.

Karl Rupp from Landegg, Austria wrote on October 13, 2016 at 7:14 am

I met Hans Petter at the SIAM CSE meeting in Boston in 2013, from which I recall being impressed by his open-mindedness and how approachable he has been. Two years later, Anders Logg arranged a public phone call to Hans Petter at the end of Anders' talk at SIAM CSE 2015 to send the audience's best regards. This will be something I'll always remember; it shows how much respect he has earned in the community on so many levels.

Michael Alley, College of Engineering, Penn State from State College, Pennsylvania wrote on October 13, 2016 at 2:54 am

Foremost, Hans Petter was scholar. Yet what I will always remember, and treasure, was his excitement about my work, which seems so small compared with his. Still, when Hans Petter liked one of your ideas, the world appeared to stop for him, and for you. His eyes lit up, his hands gestured in big arcs, and his voice welled and then exploded with enthusiasm. Hans Petter would not just approve your idea--he would embrace your idea.with a passion for it even deeper than your own. Hans Petter gave so much, of himself. In my memory, his energy was boundless. He will be missed more than words can express.

Mihai Anitescu from CHICAGO wrote on October 13, 2016 at 1:01 am

I worked with Hans Peter as editor at SISC, and met him a couple times at CSE, he was a joy. He will be missed.

Ondřej Čertík from Los Alamos, NM wrote on October 12, 2016 at 11:18 pm

I think I never met Hans in person, but we communicated over email a lot, later he invited me to contribute an article about SymPy into the Encyclopedia of Applied and Computational Mathematics. I think I might have spoken with him on the phone once. He was a super friendly person, always cheerful, and encouraging. And very nice to collaborate with. He was very modest. He invited me to visit him in Norway, but sadly that will not happen. I am happy I had a chance to collaborate with him at least on a few projects. I am very sad he passed away.

Douglas Arnold from Minneapolis wrote on October 12, 2016 at 9:51 pm

With Hans Petter's tragically premature passing we have lost a great computational scientist and a great communicator. But he leaves behind a great impact. His vision and early work on Diffpack continues to have a big influence on modern PDE solver environments, his FEniCS tutorial was the gateway to that program for many users, and his books on scientific computing have educated thousands. With his clear vision and enthusiasm he was always a pleasure to interact with. His high standards as an editor and his diplomatic skill in enforcing them benefited many of us. He will be sorely missed.

Panagiota Tsompanopoulou from Volos, Greece wrote on October 12, 2016 at 9:01 pm

Few years ago I met Hans Peter and I had the chance to work with him and the SIMULA group in Oslo. I will always remember how nice and enthusiastic he was. My deepest condolences to his family and SIMULA.

Patrick MERLOT from Oslo wrote on October 12, 2016 at 8:46 pm

I have been a one-semester student of Hans Petter Langtangen about 10 years ago. Probably like many of his students, I kept a feeling of admiration for the work this one man achieved and affection for his genuine willingness to share it to the many. I feel lucky to have met him and some of his close friends and colleagues that with him became important models for me. My thoughts are with his family and friends.

Are Magnus Bruaset from Oslo wrote on October 12, 2016 at 5:56 pm

My collaboration with Hans Petter dates back to 1993, when I became his sidekick in the development of Diffpack at SINTEF Applied Mathematics. This software package was one of the first large-scale attempts at using object-oriented techniques and high-level abstractions for creating very flexible and still numerically efficient simulators. These experiences fueled Hans Petter’s continuous search for the optimal way of developing numerical software, which led to his series of very popular Python books that have impacted researchers and students world-wide. I often think back to those pioneering days in the ‘90s, fondly remembering all the excitement, curiosity, and energy – three words that would describe Hans Petter to the very end. I will miss him – as a colleague here at Simula, and as a friend.

Tammy Kolda from Livermore, CA wrote on October 12, 2016 at 4:17 pm

It was a great pleasure to work with Hans Petter in his role as editor in chief for the SIAM Journal on Scientific Computing. He was a fantastic human being, and I will miss him very much. My sincere condolences to his family and coworkers.

Bjørn Skallerud from Trondheim wrote on October 12, 2016 at 2:27 pm

I met Hans Petter around 2000. We discussed how to improve collaboration in computational mechanics in Norway, in particular between UiO and NTNU. Then one year later Hans Petter contributed strongly to the birth of our National Conference on Computational Mechanics (Mekit) as one of our scientific board members. This conference has occurred every second year from 2001, and the next is in 2017. During the planning of the conference we also (of course) talked about music. It turned out he plays the guitar, and I play drums. So during every Mekit conference we also put in significant time for intense jam sessions in the basement under the wind tunnel lab at NTNU (trying to balance his taste for smooth jazz rock and my taste for heavier expressions). One word: fantastic. We also collaborated in the center of biomedical computations. Over the years we have met many times, sharing a beer, a meal, a discussion on how to teach mechanics, new directions for research. Last time we met was 1 June this year, on his balcony. Sun shining, good discussions, Hans Petter enthusiastic as always. Now we have lost a fantastic colleague and friend, I will miss him deeply

Karen Willcox from Cambridge, MA wrote on October 12, 2016 at 1:10 pm

Hans Petter was an exceptional colleague. His sustained commitment and service to the scientific community is an inspiration to us all. I was fortunate to have the chance to work closely with him over many hours of effort in co-chairing CSE13 and through our editorial roles at SISC. He will be missed.

Luca Formaggia from MIlano wrote on October 12, 2016 at 12:37 pm

I have met Hans-Petter approximately 15 years ago and unfortunately I do not remember the exact occasion. I remember him as an enthusiastic and visionary scientist. I was deeply honoured when he offered me to serve as Associate Editor to SISC. We will miss him.

Jack Hale from Luxembourg wrote on October 12, 2016 at 11:59 am

I met Hans Petter for the first, and sadly now, the last time, at the recent FEniCS Conference in Oslo. Prior to the conference, I emailed him to ask about Chaospy, a Python-based package for propagating statistical uncertainty through models, that he had developed with his PhD student Jonathan Feinberg at Simula. I had been told previously that he was quite ill, so it was wonderful when he replied saying that he wanted to come and talk about Chaospy. Reading the other stories on this memorial, I perhaps should not have been so surprised at his enthusiasm to meet. In the 20 minutes we chatted about Chaospy I could tell that he was truly passionate about scientific computing, Python, and the need for quality software to enable good science. He will surely leave a strong legacy that will influence the way things are done in our field.

Uli Ruede from Erlangen and Toulouse wrote on October 12, 2016 at 11:53 am

Hans Petter was a great scientist and a good fried. I remember fondly our first personal meeting, in September 1996, when he co-organized the workshop SciTools in Oslo - and in fact I have just dug out the slides that I have used for this event. I remember from this meeting how we discussed over a beautiful dinner and then a sightseeing excursion in Oslo how we would define the difference between Scientific Computing and Computational Science. Many of the scientific topics that have developed from there onwards have now become the core of CSE. They have become no less than a new discipline. For me personally, this 1996 meeting has been a corner stone and I have profited for 20 years from the continuing exchange of ideas and visions with Hans Petter.. I will miss his sharp mind, his deep insight, and a good friend.

Hans De Sterck from Melbourne wrote on October 12, 2016 at 11:10 am

Hans-Petter was a great inspiration for so many of us at SISC and in the SIAM CSE community. I was deeply impressed by him as a person, with his modesty, wittiness, sharp knowledge, fairness, good judgment. He had such a classy way to go about things. He was an example for many of us, and will be dearly missed.

Garth Wells from Cambridge, UK wrote on October 12, 2016 at 10:11 am

I am very sorry at Hans Petter's passing. I was always struck by his enthusiasm, kindness and unwavering support, even as his health deteriorated. I met Hans Petter in Chicago in 2005 at the first FEniCS workshop. Many of us present were meeting in-person for the first time, and we have since seen each other many times. I recall enjoying meeting Hans Petter for the first time, and looked forward to seeing him on the many subsequent occasions that we met. He will be sorely missed. I am grateful for the support Hans Petter provided, and he was a wonderful supporter of the FEniCS Project. I also witnessed the way he fostered new researchers at Simula, and the support and guidance he offered. His work influenced the way I teach, and has affected the way we now teach at University of Cambridge. His influence will continue.

David Keyes from Thuwal, Saudi Arabia wrote on October 12, 2016 at 9:25 am

Hans Petter was a force of nature on behalf of CSE. Springer’s Lecture Notes on CSE could not have found a better author friend. SIAM’s Journal on Scientific Computing grew a strong CSE flavor during his editorship. The SIAM Conference on CSE that he co-chaired in Boston was a breakthrough meeting in terms of overall attendance and multidisciplinary outreach. SIMULA loses a star and the world of CSE loses an eloquent interpreter and its greatest enthusiast.

Mikael Mortensen from Oslo wrote on October 12, 2016 at 8:07 am

Unlike most people at Simula/UiO I met HPL through his books. I was doing advanced modelling of turbulent combustion and dabbled with programming and implementation of my models. I vividly remember how his ”Python Scripting for Scientific Computing ” struck me like a bomb, and for a long time it was my regular companion on the train commuting for work. I was so impressed by his enthusiasm that spoke to me through the lines. I had been living under the misconception that I knew a thing or two about programming, and then this guy shows up, miles ahead, pulling me away from physics and into the world of scientific computing. Then I met him in person! At first I was seriously starstruck, then shocked by his age, and then finally just amazed by his fantastic personality and sense of humour. It was not just his books that were inspiring! Today I’m very sad that he is gone, but I feel privileged to have met him and to have counted him as a friend. He changed the course of my career back to academia and I owe it to him that I hold my current position as Associate Professor at UiO. I will forever be grateful and I miss him deeply. Work will never be the same.

Konrad Hinsen from Paris wrote on October 12, 2016 at 7:25 am

I first met Hans-Petter at a conference in Switzerland, so long ago that I can't remember the exact year. We shared a hotel room because the conference hotel was overbooked for some reason. We ended up collaborating on a project to do parallel computing in Python (at a time when this was still exceptional). The last time I saw him was at EuroSciPy 2010. I wasn't aware of his illness, so the news of his passing was quite a shock. I will remember him as an enthusiastic, insightful, and kind person.

Fernando Perez from Oakland wrote on October 12, 2016 at 5:54 am

I first met Hans Petter when we organized an event for the SIAM 2009 CSE conference about the use of Python in scientific computing. I was struck by his generosity and giddy enthusiasm for sharing knowledge and ideas. Over the years we had multiple opportunities to collaborate further, and in 2013 I was able to spend a few days visiting him in Oslo. That visit remains one of my most cherished "academic travel" memories, and I kept looking for a way to accept his invitation to return. Sadly, that shall not be... Our last collaboration was in setting up residence for Min Ragan-Kelley as a scientist in his group, so that Min could continue his work on Project Jupyter from Norway. This came unfortunately as Hans Petter was falling ill, but he was still able to put everything in place for Min's success at Simula. In the world of big academic egos, Hans Petter stood apart for his kindness and genuine generosity. I am lucky to have had the privilege of enjoying it in person. We will all miss him deeply.

Gael P Varoquaux from Paris wrote on October 12, 2016 at 5:06 am

I knew of Hans Peter from his book on computational sciences and Python and his teaching activities. I met him when we invited him to give a keynote at an early EuroScipy. He was a kind and enthusiastic man, with a vision. His vision was about sharing knowledge and fostering ideas. We kept exchanging emails since. He will be sorely missed.

Travis Oliphant from Austin wrote on October 11, 2016 at 10:31 pm

I only met Hans Petter once and that was only briefly. I thanked him for his impressive contributions to Python and Science and he was gracious and kind. I remember being impressed by his research work and contributions and feeling at little pain because I had given up the academic world. He was a model of success in academia and in life. We will miss him!

Andy Terrel from Austin, TX wrote on October 11, 2016 at 9:49 pm

I met HPL in graduate school. First in print as his words opened my eyes to the power of computational science and python. Then in real life as he came to our campus to participate in the FEniCS project workshop. Of all the people I have known, none have been a greater champion of the unrelenting pursuit of open source scientific software. His words were inspirational. His work was transformational. His dedication was undeterred even in the face of illness. His contributions to the scientific field will be felt for generations.

Anders Logg from Smögen wrote on October 11, 2016 at 9:34 pm

HPL was a truly impressive man in so many ways. It is hard to understand he is gone, especially when I'm currently sitting here editing one of his latest manuscripts, making adjustments according to emails and fixmes he added only a few days ago. I was lucky to meet him and it was a privilege to work with him on one of his new books. His work and inspiration will live on.

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