Τι κάνεις FOSSCOMM 2019

Thanks to the sponsorship of Fedora, I was able to travel to Lamia, Greece from October 10 to October 14 to attend at FOSSCOMM (Free and Open Source Software Communities Meeting), the pan-Hellenic conference of free and open source software communities.

Things I did in the event:

1.- Set up a Fedora booth

I arranged the booth during the first hours when I arrived Lamia. The event registration started at 4:00 p.m. and thanks to the help of enthusiastic volunteers and Alex Angelo (I met him in GUADEC 2019), the booth was all ready to go since the first day of the event.

The Fedora project sent swags directly to the University of Central Greece, and I created my own handmade decoration. I used Fedora and GNOME ballons to have a nice booth 🙂 Thanks to the tools provided by the university I was able to finish what I had in mind:

2.- Spread up the Fedora word

When the students visited our Fedora booth, they were excited to take some Fedora gifts, especially the tattoo sticker. I was asking how many of them used Fedora, and most of them were using Ubuntu, Linux Mint, Kali Linux and Elementary OS. It was an opportunity to share the Fedora 30 edition and give the beginner’s guide that the Fedora community wrote in a little book. Most of them enjoyed taking photos with the Linux frame I did in Edinburgh 💙  Alex shared also his Linux knowledge in our Fedora booth.

3.- Do a keynote about Linux on Supercomputers

I was invited to the conference to do a talk about Linux in supercomputers. Only 9 out of 42 attendees were non-Linux users. However, I am so glad that they attended to know what is going on in the supercomputer world that uses Linux. Then, I started by asking questions about Linux in general, and some linuxers were able to answer part of the questions but not all of them. I have been told by professor Thanos that Greece has a supercomputer called Aris, as well as the students were aware about GPUs technologies. When I asked a question about GPUs, a female student answered correctly about the use of GPUs and that is why she won the t-shirt of the event I offered as a prize to the audience. You might see my entire talk in the live streaming video. 

4.- Do a workshop of GTK on C

I was planning to teach the use of the GTK library with C, Python, and Vala. However, because of the time and the preference of the attendees, we only worked with C. The workshop was supported by Alex Angelo who also traduced some of my expressions in Greek. I was flexible in using different Operating Systems such as Linux Mint, Ubuntu, Kubuntu among other distros. There were only two users that used Fedora. Almost half of the audience did not bring a laptop, and then I grouped in groups to work together. I enjoyed to see young students eager to learn, they took their own notes, and asked questions. You might see the video of the workshop that was recorded by the organizers.

My feelings about the event:

The agenda of the event was so interesting, I was quite sad to not attend because I had to take care of the booth, and most of the talks were done in Greek. As you can see in the pictures, there were a variety of technical talks in charge of women. I was impressed by Greek ladies because they are well prepared, most of them were self-taught in Linux and in trending technologies such as IoT, security, programming, Linux, and in bio-science.

Authorities supported this kind of Linux events and I think that was an important factor to have a successful event. Miss Catherine and Mister Thanos were pictured with minorities, women and kids were very excited to be part of FOSSCOMM 2019. Additionally, its local government also supported this event. Here a post in the magazine.

Greek people are warm and happy.  Thank you so much to everyone for the kindness!

Food for everyone

I was surprised by time and schedules, they started the journey every day at 8:00 am and the talks finished at 8p.m. The lunch break was set at 2:30p.m. and a local guy told me that just for breakfast they usually take a cup of coffee. We had a very delicious and consistent dinner on the first day of the event with the professors of the Informatics and Biology department of the University Central Greece. Free lunch and coffee breaks were served carefully to all. I enjoyed Greece food, we had a variety of salads and sweeties. 

Turistic places I visited

I only had a few hours before leaving Lamia, I had time to visit the castle and the museum where I learned more about the different ancient eras and legends of Greece.

Special Thanks

Thanks to Alex for being my local guide during the whole event! Thanks to Iris for the welcoming, to Argiris for the invitation and the t-shirt he promised me, and to Kath for being so nice in the thousand pictures we took and for the touristic guide and her help.

Thanks to Stathis who encouraged me to apply to FOSSCOMM, to each volunteer for the help they gave me and all the effort they did, I know that most of them live an hour and a half far from the university. Thanks again to Fedora for the travel sponsorship!

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A reason to go to GUADEC

There is only one reason to attend GUADEC: To learn about GNOME.

You may not know much about the GNOME project or the GNOME community. From my experience in the GNOME community for more than eight years, I can list some reasons to get to know more about it:

1. GNOME is a worldwide project and community

It is usual that people work in a company that has functional areas such as marketing, technology, human resources, accounting, and finance. It is also usual that people work with other local people face-to-face in a fixed schedule on weekdays. GNOME has the same functional areas managed by people from many parts of the world. Each person has a different way of working, different time zone, and different culture – but they all have the same mission: to improve the GNOME software and the GNOME community. You are more than welcomed to contribute to GNOME as a developer, designer, translator or any role you prefer!

Pictured on the left, we see Linux enthusiasts: Nuritzi and Sri from the USA, Sigu and StellaMaris from Kenya, and Julita from Peru 😉  On the right side, all the GNOMEies gathered at GUADEC 2019. You can get GNOME as a final user or get the code in gitlab as a developer.

2. GNOME creates breakthrough technologies

I got to know about Red Hat because I attended GUADEC 2012 and I saw Marc Andre and Zeeshan proudly wearing their red hats. Now in 2019, I am aware of the partnership of GNOME with Purism and was able to see the elegant work of Tobias Bernard at GUADEC and how GNOME can now be used for Linux smartphones. I want to also highlight the work of Peruvian Fabian Orccon, who is doing volunteer technical work for Cheese. This application captures static faces to apply effects, and now with Fabian’s help, it detects faces in movement and applies effects used in technologies like Snapchat and on Facebook. Finally,  at this GUADEC, Lubosz Sarnecki from Collabora moved GNOME to another reality. He used Virtual Reality(VR) to simulate a virtual desktop environment.
These three innovative efforts I just mentioned came from three of GNOME’s former Google Summer of Code (GSoC) students. You can learn more about Google Summer of Code opportunities for GNOME here.

3. GNOME supports and empowers all of its members

GNOME has defined guidelines for members who want to participate in GNOME. Following these guidelines, I have designed some initiatives that I have applied within my local Linux community in Peru: Peru Rumbo GSoC 2018, GNOME PERU Challenge 2017 – I,  and Lets CONTRIBUTE Peru. These were some of the volunteer programs I created in order to promote the use of and contribution to GNOME in my country. GNOME believed in my efforts and supported these ideas by providing the material resources I needed as well as some online support from other GNOME members. I feel that I only succeed once because Cesar Fabian Orccon was the only Peruvian that also became a GNOME Foundation member and not my other students. Even if I made mistakes along the way, GNOME appreciates my effort, time, and money I invested during more than 8 years.

Regarding my own story, I started in GNOME as a technical writer, and over the years I became a representative of GNOME and a speaker at Linux events. For instance, I gave a talk in Portland at the API 2017 conference where I did a workshop using GTK and C. That is only part of my experience with GNOME, and that is also the case for other members such as Carlos Garnacho, Maria, Nuritzi, and Sebastian, who works in Ubuntu. At this year’s GUADEC, I met Sigu and StellaMaris who have promoted Free Software in Africa for around four years!  Pictured on the bottom left: GNOME members are taking selfies as a part of a workshop at this year’s GUADEC.

4. GNOME allows you to leave a legacy

GNOME has more than 20 years of existence and it has also been translated into more than 20 languages thanks to the contribution of volunteers around the world. In order to have a successful Linux project, you must attract a new generation of contributors and pass along the know-how to them. In this matter, GNOME has joined the GSoC program and Outreachy to reach newcomers.
I have met the GNOME students in Thessaloniki and I am glad that Carlos Soriano keeps this effort since he was a previous GSoC student and he is sharing his expertise with newbies.

5. GNOME helps build friendship around the world

First, you meet someone and then it can be hard to make the change from acquaintances to friends. I am so glad to share that I have been invited from GNOME members to be part of their lives and they kindly hosted me in their houses when I traveled abroad. That is the case for Andre Klapper in 2012 when we stayed at his apartment to attend the Documentation Hackfest in Brno. In 2014, I visited UK at Kat’s place, and in 2016 in order to attend to the ISC conference (a non GNOME conference), I stayed at Tobias Mueller’s house and I met his lovely wife.

It is priceless that somebody trusts you enough to give you the key of their house. It was very exciting to see these people again at GUADEC 2019! Petr Kovar’s is just in the collection of photos because I had no other choice 🙂 Felipe Borges taught me GTK on Python once in a Hackfest, and keep many other valuable stories in my mind from Javier, Sam, Rosanna, David and Bin Li that were also pictured for this post. Finally, even though I did not visit Nuritzi’s home, I feel that she is my friend not only because she supports my ideas and initiatives, but because a real friend tells you in your face good and bad things in order to be a better person. Nuritzi did that in this GUADEC, and I will try to behave better for the sake of humanity. I will post Zeeshan’s photo when he will take me on his plane! 😀
Additional thanks To Federico Mena, Marina, Karen, Shaun McCance, Phil Bull, Siska and all the GNOMErs that did not attend the GUADEC 2019 but they are definitely in my mind and heart 💜

6. GNOME is constantly working on user-friendly changes

A project exists based on a user’s need. Nowadays, an IT project must be enough to solve the needs of two generations such as millennials and members of Generation Z. These two generations are closely impacted by the presence of technology, then GNOME has been reinvented during the latest years. The first substantial evolution I witnessed was the implementation of  GNOME 3.x. This effort is constantly improved by developers of GNOME, due to the ubiquity and online-oriented information demand. The GNOME technologies that are created must be adequate for the sake of the project and for all its members and users. There is also a board of directors of GNOME that are supervising all the efforts done by the GNOME members.

Pictured are Philip Chimento who is in charge of GJS, the GNOME Javascript engine, and Robert McQueen who is the CEO Endless, ex CTO and co-founder of Collabora and long-term contributor to FOSS projects like GNOME, Flathub, Flatpak and freedesktop.org, and currently serving as the President of the GNOME Foundation Board of Directors.

You might see the full schedule of the projects presented at GUADEC 2019 here.

7. GNOME rewards your efforts

Meritocracy is a basic principle that GNOME has demonstrated over the years. As GNOME people contribute to the GNOME project and community, they are prized by being sponsored to attend different Linux conferences around the world. In my case, GNOME recognised my effort by featuring me as a people side of GNOME. It definitely raised my confidence. Moreover, I feel strongly connected with GNOME when I read posts of other GNOME international members such as Philip Chimento and Felipe Borges where they showed empathy towards my work.

In this GUADEC 2019, I met again and shared my table with the GNOME Asia members. I had the honour to travel to Asia to meet the strong GNOME Asia community in 2015. Glad to talk to BinLi, he is one of the most active members for several years and works for Open SUSE in China.The “Bingo” prized the effort that some people did in this GUADEC to meet GNOME in deep. I will never forget that I won twice! That is the first time in my life that  it happened!

8. GNOME is an important part of my life

Over the past 8 years of contributing to GNOME, my life has changed from the routine to a life of trips, and continuous learning because the world of technology also constantly changes. GNOME gave me trust in myself and that is, in my eyes, more valuable than anything else. I have moved to the USA and the UK in the last two years. Starting off has been so difficult since living abroad implies acquiring new mindset and ways to behave in a different culture. However, wherever I go, I try to spread the Linux word, especially the GNOME and Fedora word. You can see that in the two interviews that ORNL did to me in the USA: 1, 2; and here is the video that summarizes my volunteer work as the general organizer of  Linux at Edinburgh, an event where a did a talk about GNOME and Fedora.

Thank you so much again GNOME for second 0.3 in GUADEC 2015, the 1:31 on GUADEC 2012, My GUADEC 2014, My GUADEC 2017, and My version of the Desktop Summit 2011, My own video of my talk at GUADEC 2012 and my lighting talk at GUADEC 2015.

9. GNOME made challenge myself

I have recently completed my masters in Computer Science when I won the OPW 2011 for GNOME. I started in the GNOME documentation team, and then I realized that learning Linux will help me get better career opportunities. Unfortunately, I have never been hired by any partner company of GNOME such as Red Hat, Collabora, CodeThink, Canonical or Purism as most of the current GNOME members are.  However, my entrepreneurship allowed me to achieve my Red Hat Certified Professional and then I was able to work in IBM Peru. This opened me other doors such as being a Linux teacher in universities in Lima, Peru. Later, I was involved in High Performance Computing researcher projects.

I dare to say that GNOME made me find myself as a blogger, photographer, teacher, sysadmin, international speaker, developer, IT event organizer, and nowadays I am acquiring skills as a researcher in the HPC field.Taking GNOME people’s backs represented my challenge at this GUADEC because I usually take pictures of people’s fronts. I am also excited to see ARM as part of the GNOME sponsors.

10. The GNOME heart is left wherever the GUADEC is held

Throughout these eight years, I met GNOME communities around the world. I got fascinated when I saw in person different volunteer workgroups making possible GUADECs. This GUADEC 2019 in Greece has definitely a lovely group behind the scenes.Thank you so much Efstathios Iosifidis, Mariet Vaina, Eirini Basdani and all the team! 👍

Special thanks for the proofreading service to Nuritzi Sanchez and KittyKat 

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Building a foundation of HPC knowledge

It is said that life is a series of decisions. In my case, I was living life as light as a feather, but passionate in anything at the same time. I like challenges and I did not want to be just a woman in computers, I wanted to be a woman that works with supercomputers! Three years ago, I found by chance the HPC (High Performance Computing) program offered by the University of Edinburgh while I was considering higher studies in HPC, since this field has many areas to flourish. Despite my previous HPC experience with my internship at ORNL in the USA, and the ISC 2016 event in Germany, I decided to move to Scotland to learn more about HPC.

The EPCC (which offers this intense HPC year program) has been the international centre for excellence in high-performance computing for over 25 years. I’ll share some memories:

The beginning

I was impressed by the number of ladies I met as classmates. Usually in the “IT world” there are very few women compared to men. The following picture shows that our HPC master group had 14 men and 10 women (1 from the UK, 1 Germany, 1 Peruvian, 7 China).

During classes and workshops

The curriculum for courses are previously arranged in advance by the teachers and teaching assistants and published one week before on the intranet. They consist of the theorical materials and practical exercises to support the theory. Some reinforcing workshops were also used in order to address questions and concerns.

Additionally, a personal tutor is designated in order to help us with any university subject.

Work as part of a group

Some courseworks were set in order to develop our skills of working as a group. Soft skills and other non-technical skills are also part of our educational evaluation. Dealing with students from multicultural societies was a little challenge for me at the beginning. With time, I discovered and learned from different studentship habits and actions.

Communication is the key in any healthy relationship in any circumstances.

Visiting Edinburgh in group

We did not share many moments as a unified group because of the deadlines of the intensive Master program. The first time we were together, it was arranged by the school to have an all-you-can-eat buffet with dishes from all over the world. A second big-group meeting was gathered by the initiative of the Chinese group. We went to the Edinburgh zoo, where we had lots of expectation for the penguin parade! The last one was a two-hour walk to the Arthur’s seat during the first week of our second semester. It was recorded  🙂

I have to say that the Chinese group demonstrated to be a strong community.

My failures and achievements

One of the first coursework that represents a challenge to me was our first MPI assignment, which consisted of divide a figure into pieces, then enhance it, to finally reconstruct it using many MPI processes. At the end, we were asked by the school to deliver a code and a report. Figures of different sizes were used for the experiment and thanks to the help of Holly and Jasmin I was able to complete it! Another challenge I remember I had, was the Student Cluster Competition SCC. I left the team since it represented an extra effort that I was not able to manage at that time.

The experience was useful at the end because my dissertation included the CP2K HPC app.

Inspirational people and friends

Living abroad implies facing hard times, special thanks to Holly, Ruwaida, Racky, Huahua, Andreas and Cris for their understanding and help any time I asked. They stood by my side not only as good classmates, they were very friendly even in my complex mood :p

Meeting pluricultural people and moreover, living together in Bayes was “the experience”.

Unforgettable moments

The picture in the left was taken the first Sunday we meet in Bayes to complete the PS assignment. It was funny to see other groups watching us through the windows as a weird group. The picture in the right was taken in my apartment by my dear Holly, who was trained by me the whole year to have amazing selfies. I am glad she made it 😀

Uncountable stories that at the end someone remembers how others made you feel.

Leveling up people

Special thanks to those people that trusted in myself when I struggled to achieve something related to the master. Thanks to Vanya Yaneva for her support during the practical sessions, thanks to my supervisor during dissertation time and thanks to Abby!

The end

After presenting our dissertation summaries, the school prepared a gathering to close out the university year. I could not believe that this stage in my life finally ended.

All this students were so hard worked and smart in researching. I learned a lot from them.

Thanks EPCC

Scientists of EPCC were so helpful with my questions in the kitchen! Thanks to all EPCC!

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OpenMP User Conference 2019 in Edinburgh

The OpenMP user conference 2019 was held in the University of  Edinburgh by EPCC that hosted 10 speakers in person and one remotely over two days for around 30 attendees.

Day 1- Tuesday 4th June

  1. Hands-on Tutorial

I joined the Programming Your GPU with OpenMP: A Hands-On Introduction presented by the Professor of High Performance Computing at the University of Bristol, Simon McIntosh-Smith. He started with an overview of OpenMP and the difference of the terms used in the GPU programming model, the host, the device, and the clauses used in the target device. After that, we started the active learning by interacting with the ARM supercomputer called IsambardInitially, we run a basic serial program to add vectors, where the clause #pragma omp target was set in the processing loop.Usually, the serial version took more time than the parallel job. We need to check in deep in case we have a different result.

It was also explained how to read nvprof, a profiler CUDA toolkit. The command used was nvprof – -print-gpu-trace ./vadd. The first two lines show the cost of offloading in percentage. The calls from the host to the device are mostly greater than the calls from the device to the host after doing the reduction calculations in the device.

Later, the levels of parallelism were explained where the team of threads to be distributed follows the flow: target → device → compute unit → processing element. The term team of threads to be distributed is defined to be used inside the device. The jacobi_solver exercise was so useful to understand how the team of threads works. In this example, a pointer to a fixed array of floats that needs to be explicitly defined in the code as follows:Screen Shot 2019-06-04 at 12.39.03 PM.png

After adding the omp directives, we have that the parallelised version goes twice faster:Screen Shot 2019-06-04 at 12.43.00 PM

To control the memory movement, the target enter data and the target exit data allows data construction to create a data region. These clauses are set in the area of swapping data because the exchange is expensive. The target enter data allocates and copies data to the device, and target exit data directive copies back or destroys the data.Screen Shot 2019-06-04 at 4.25.18 PM

After these configurations, a very good optimization of the data movement is noticeable reducing the execution time 10 times from the serial version of the jacobi_solver.Screen Shot 2019-06-04 at 4.19.34 PM

2. Advanced OpenMP: Performance and 5.0 Features

An interesting talk about the performance of OpenMP was given bythe Senior Principal Engineer of Intel Corporation in the U.K., Jim Cownie. He shared OpenMP programming knowledge and parallel concepts related, as well as the best practices used.

Day 2- Wednesday 5th June


Nine talks were presented, including a remote presentation of the Director of Supercomputing Center of Excellence at Cray Inc., John M. Levesque who explained how to read the report provided by the CrayPat tool. I highlight these two efforts of the industry in pictures, Dr. Glover from MetOffice trying to accelerate UM and NEMO, and the representative of ARM, Oliver who optimized the performance of OpenMP intranode.

In the academy, the FFLUX optimization by Benjamin Symons from the University of Manchester inspired me to do a comparison with the application I am studying. The OpenMP Parallelisation of Quantum Computing Simulators by Youssef Moawad was also impressive to me, he did an excellent job in his presentation (including the rainbow:).


Experts in OpenMP offered themselves to be asked about OpenMP. They are working towards OpenMP5 and the compatibilities with upcoming versions as GCC 10 and doing a common collaboration to adapt this interface to different HPC architectures.Food of Event

We met new HPC fellows during lunchtime, a Ph.D. candidate from Egypt Youssef and the Ph.D. student from the University of Manchester. Thanks again to Holly and Andreas H.

The OpenMP community in the U.K.

We did not have a photo group, but we were able to exchange ideas during the break time.

Special Thanks

Thanks to Dr. Bull for the invitation that let us enhance our skills, and to Professor McIntosh-Smith. It was exciting to meet in person the author of a paper I’ve referenced.

Good event in general! It would have been nice to have a couple of workshops and 45 minutes per talk. The projects were very interesting, but some talks lasted 15 minutes.

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EuroHPC Conference 2019 in Poznań

I was invited to do a talk to the EuroHPC conference in Poznán from May 13 to May 17. The experience was more than satisfactory from the very beginning to the end. Being part of the first-class HPC event was convenient from my perspective to learn from HPC  experts, improve my HPC knowledge and engage myself with this profession by increasing my networking in this very important field. Some thoughts from the event as follows:

HPC Topics

Several topics were presented as it was planned in the Timetable in regards to the HPC technologies and infrastructures that support scientific projects in Europe and around the world, the improvements done and the needs towards the exascale computation. From all the HPC topics, the eduGAIN project conferred by Erik Huizer captured my attention since I saw a world map and my country was not included yet in the “Federation of the Federations project” nor as part of any HPC team. I talked with Dr Huizer about it and he explained to me that the project was still in progress. Another project that took my eyes was the ambitious “HPC & Water-energy- food-environment- economy system analytics” project presented by Julien Harou that requires 750,000 model runs for n random seeds. From what I heard, most of the efforts have been done to support quantum projects in Europe. Finally,  I enjoyed so much the presentation done by Dr Marina Becoulet from France because she was able to model an HPC magnetic fusion using maths foundation, physics and she was consistent while she explained the emerging study that used MPI and OpenMP towards the exascale era.

On May 15th, I decided to attend to the PRACEdays Industrial Track and the PRACEdays Scientific Track 8: Computation Science/Towards exascale. Dr Chris Jhonson from EPCC explained the SHAPE project in Europe to promote the use of HPC resources. Studies that engaged me most were presented by Daniele Rispoli with the Immersion Cooling for HPC, the FEniCS-HPC mesh adaptivity on heterogeneous architecture by Ezhilmathi Krishnasamy, and Multi-scale Quantum Transport Simulations in thousands of cores the using graphene by Jose Garcia. You might see more of the content of these projects hereHPC Networking

It was very interesting to see HPC projects that demand exascale computation in the domain of chemistry, physics, astronomy, aeronautics, and in the education field using Federation technologies. HPC professionals from Greece like Evangelia Markidou and Erik Huizer were so cordial to me during the event and it was a pleasure to meet them. Thanks! My HPC talk

The title of my talk was “HPC: Challenge Accepted” where I shared my experiences and lessons learned as an international student of the Master in HPC at the University of Edinburgh as part of the session “Equality and Diversity in HPC“. I divided my talk into three parts: Thinking in Parallel, Studentship differences Peru – UK, and Culture Shock. HPC Teams

I met researchers from the Barcelona Supercomputing Center that are originally from different countries than Spain such as Alejandro Ortiz, a PhD student from Mexico who gave me some pieces of advice as LATAM professional in Europe, José García from Venezuela, a postdoc who is an interdisciplinary professional in physics with a computer science background, and Lawrence Adu from Ghana, another outstanding HPC professional. Moreover, I also had the chance to spend more time with scientists from Edinburgh Parallel Computing Centre of the University of Edinburgh as Dr. Chris Johson.

HPC diversity

It was a nurturing experience to exchange project ideas and HPC endeavours with different researchers around the world. I met Phuong from Vietnam who studies in Stockholm, Iker, a biologist PhD student from Valladolid who is living in Barcelona, Alejandro, a PhD from Mexico who is doing a PhD in BSC, Ezhilmathi from India who studies Maths and HPC to do CDF simulations, and Lawrence Adu from Ghana who is also working in BSC Spain.

Food and Social Events

I was sponsored by PRACE organizers and they booked a room in the same hotel where the event was held. Excellent food and other state-of-the-art services were provided during my visiting days in Poznań. Diversity of international menus was also nicely offered.  Walking around the city

Getting to know this historical place was a rewarding experience considering the colour of the buildings and the art involved. Lots of statues of mythological creatures surround the Old Market Square of Poznań. Even though it was raining that day, I was able to record good memories there. Special Thanks

To Dr. Debora Testi from CINECA for trusting in my work along these years. Thanks for giving me this amazing opportunity that allowed me to empower my developing HPC career, and to maintain confidence in my HPC training. I also want to express my gratitude to Michał Pilc, a local HPC professional from Poznań who works in the Supercomputing Centre of Poznań for being welcoming and for patience with my doubts in HPC supercomputing centres. Lastly, another HPC professional from the University of Manchester, Lee Margetts who paid attention to my talk and he showed empathy with my situation as a foreign student. Thanks so much again for being so kind, and admirable HPC representatives in Europe. Thank you so much Marjolein Oorsprong, OfCores Events and all the attendees!  🙂

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Applying OpenMP directives

The Jacobi method is a usual method to solve partial equations in HPC situations such as pollution diffuses throughout a pipe applying the Laplace’s equation for diffusion.  A way to parallelise this solution when it is coded is by using the geometric decomposition with Epiphany.

From now, the serial version of the code has a runtime of 4256258 ns. We are going to use OpenMP directives to check how faster is going to be the runtime of the parallel version.

Since loops provided a chance to parallel the code, we are going to use the directive above the two loops with the option collapse (2) and declare all the variables involved as private or shared. The reduction also was set to use the value of bnorm outside the parallel region.There is another parallel region defined by loops to find the value of rnorm (where the reduction was applied). The default nonce will force the declaration of private and shared variables. Notice that there is no need to put brackets after the parallel for directives.The parallel for was also applied in the jacobi iteration. In this case, it was not necessary to use the firstprivate variable which takes the previous value before entering to the loop, it can change inside the loop, and have the same value after the loop as it was entered before.Due to the race condition of threads that are running in the program, there is a swapping zone that ought to be controlled by an OpenMP directive one by one. It is possible to achieve this with the single directive to block other threads job while one is executed.* The program was run with 16 threads (export OMP_NUM_THREADS=16) and different schedules were set such as schedule(static), schedule(static,4), schedule(dynamic), schedule(dynamic,4) with the respective runtimes. Finding the lowest runtime with the static schedule: 431520 ns.

The parallel version then turned to be 10 times faster than the serial version!

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Hybrid MPI-OpenMP

A myriad of applications are using the combination of OpenMP constructs and MPI library in order to improve their performance. You might start MPI with this great Website 🙂

Once you have a MPI program, you may include some code in order to make it hybrid:

  • Add the OpenMP header: #include <omp.h>
  • Declare request and provided variables in order to check the level of threads support.
  • Initialize the MPI environment properly, instead of int MPI_Init(&argc, &argv), use MPI_Init_thread(&argc, &argv, MPI_THREAD_FUNNELED, &provided); In this case, I choose the type Funneled but you may choose the style Master-only, Serialized, or Multiple. You can see further information about this here.
  • Define the parallel block with the directives pragma parallel omp including the default, firstprivate, private and/or shared variables as your program was set.

  • In your Makefile, set the FLAG= openmp or qopenmp (depends on your compiler).
  • Load the modules and run it as it is, a MPI program.

The performance was test as it is shown in the table having the best option with 36 processes and 1 thread using the Funneled type. Later, the style MPI_THREAD_SINGLE with 36 process and 1 thread was set, achieving 0.0532 achieving a speed of 0.9797 with this type.

*** Compared the Single style to the Funneled, this latter one was faster. ***

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