Connecting the dots

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Parallel Debugging with a Serial Debugger

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Parallel Debuggers are important tools when trying to eliminate bugs in parallel programs. Commercial parallel debuggers are expensive. In this blog post I will show you a free and open source alternative which is good enough for education purposes and for small codes. Suppose you want to debug the famous cpi.c code which computes an approximation to pi by a parallel numerical integration. This demo uses the free Data Display Debugger (ddd) which is based on gdb but has a nice GUI. Step 1, compile: mpicc -g -o cpi ./cpi.c Step 2, run (without a debugger): mpirun -np 2 ./cpi Step 3, run with the free Data Display Debugger (ddd) : mpirun -np 2 ddd ./cpi The last command will open two MPI processes (instances) of ddd each running cpi, see screen capture: Finally, I enclose here a short video which I hope is convincing: hi-res version:  https://youtu.be/N_J4NKJkuMs Happy (Free) MPI debugging!
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High-Performance Linpack

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 HPL Benchmark on my laptop It's the Top500 season time. I therefore tested HPL on my laptop using Intel's latest OneAPI version 2021.1.10.2261. The laptop specifications are obtained from lscpu : $ lscpu Architecture:                    x86_64 CPU op-mode(s):                  32-bit, 64-bit Byte Order:                      Little Endian Address sizes:                   39 bits physical, 48 bits virtual CPU(s):                          8 On-line CPU(s) list:     ...
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The End of Grid Computing?

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In the year 2003 the MIT Technology review ranked "Grid Computing" among the 10 Emerging Technologies That Will Change the World [1]. We are now four years later and something is not going well with "Grid Computing". An indication that there is a problem can easily be seen by looking at the "Google Trends" plot for the term "Grid Computing": (click on the image to get the current trend). This finding can be compared with another buzz word, "Virtualization", which is older than "Grid Computing" and yet is gaining more and more momentum: There is however one exception. The Academic Grid is still having lot's of glory thanks to the huge heavily funded European (EGEE) and other US projects. When LHC data will start to be taken at CERN it will reach it's top importance. But, it seems that for other scientific projects Grid Computing is not going to be such a success. It will remain as "Nice to have" but will never...
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