Why Do All My Open MPI Processes Have Rank 0?

macos openmpi homebrew
aperiodic picture aperiodic · Oct 28, 2010 · Viewed 10.5k times · Source

I'm writing a parallel program using Open MPI. I'm running Snow Leopard 10.6.4, and I installed Open MPI through the homebrew package manager.

When I run my program using mpirun -np 8 ./test, every process reports that it has rank 0, and believes the total number of processes to be 1, and 8 lines of process rank: 0, total processes: 1 get spit out to the console.

I know it's not a code issue, since the exact same code will compile and run as expected on some Ubuntu machines in my college's computer lab. I've checked homebrew's bug tracker, and no-one's reported an issue with the Open MPI package. I'm at a loss.

Answer

powerrox picture powerrox · Mar 4, 2011

Check which mpirun you are invoking. The mpirun that is being executed is launching 8 independent instances of the binary. So each instance is an MPI application with a universe size of 1 and rank 0.

Also, unless you are planning to run the final code on a cluster of OS X boxes, I highly recommend installing a Linux version in a VM, like virtualbox, to test & develop these codes.

Related questions

How do I install pip on macOS or OS X?

I spent most of the day yesterday searching for a clear answer for installing pip (package manager for Python). I can't find a good solution. How do I install it?

Read More
Find (and kill) process locking port 3000 on Mac

How do I find (and kill) processes that listen to/use my tcp ports? I'm on mac os x. Sometimes, after a crash or some bug, my rails app is locking port 3000. I can't find it using ps -ef... When …

Read More
bash: pip: command not found

I downloaded pip and ran python setup.py install and everything worked just fine. The very next step in the tutorial is to run pip install <lib you want> but before it even tries to find anything online …

Read More