Parallel Debugging with a Serial Debugger

-
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!

Comments

Post a Comment

Popular posts from this blog

The End of Grid Computing?

-
Image
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...
Read more

[mpich-discuss] Errors while testing MPICH2 on Vista

-
[mpich-discuss] Errors while testing MPICH2 on Vista Guy Tel-Zur gtelzur at gmail.com Sat Oct 24 14:39:26 CDT 2009 Previous message: [mpich-discuss] MPI-3 Fortran feedback Next message: [mpich-discuss] MPI function to test a machine alive or not. Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] I am trying to test a fresh installation of MPICH2 (version 1.2) on Vista32 and get the following errors: c:\temp>"c:\Program Files\MPICH2\bin\mpiexec.exe" -n 4 cpi.exe Please specify an authentication passphrase for smpd: passphrase, e.g. behappy*> Error while connecting to host, No connection could be made because the target machine actively refused it. (10061) Connect on sock (host=user-PC, port=8676) failed, exhaused all end points Unable to connect to 'user-PC:8676', sock error: Error = -1 I will appreciate any comment. --Guy -------------- next...
Read more