Hello, > The code was pretty simple. I was trying to send 8MB data from one > rank to other in a loop(say 1000 iterations). And then i was taking the > average of time taken and was calculating the bandwidth. > > The above logic i tried with both mpirun-with-mca-parameters and without > any parameters. And to my surprise, the performance was degrading when i > was trying to manipulate. That sounds strange. So did you re-use the communication buffers? Did you try to run some existing benchmarks like Netpipe [1], IMB or Netgauge [2]?
> Now I have another question in mind. Is it possible to have IB Hardware > Multicast implementation in OpenMPI? I have gone through the > issues/challenges for the same, but also read couple of people who have > successfully done it for Ethernet/Giga-bit Ethernet and IPoIB ofcourse in > experimental stage. Actually i want to contribute for it in OpenMPI and > need the help for the same. As far as I know, there are two groups/people working on this. Andy Friedley implements a "traditional" ACK based approach (like the one that the OSU folks published about some time ago) and I implemented a new idea for extreme scale (see "A practically constant-time MPI Broadcast Algorithm for large-scale InfiniBand Clusters with Multicast" [3]). I know that my version is still unstable and has some problems. But I'm working on this. Best, Torsten [1]: http://www.scl.ameslab.gov/netpipe/ [2]: http://www.unixer.de/research/netgauge/ [3]: https://www.unixer.de/publications/#hoefler-cac07 -- bash$ :(){ :|:&};: --------------------- http://www.unixer.de/ ----- Computer scientists are the historians of computing. -- Gordon Bell
