Hi everybody! First of all I want to congratulate all of you because the quality of the community, I have solved a lot of doubts just reading the mailing list.
However I have a question that I can not solve... Until now I though that all the collective operations have an implicit sincronization, but I can see that this is not true at all (because optimizations?). Then, after searching a little bit on the web I saw that there are several implementations of the reduction in openmpi, in fact there are 6 possible algorithm (at least on OMPI 1.6) that you can use by mean of the mca parameters... I thought that one of them behaves as a synchronization but after execute a test with each one, no one behaves as it. Then my question is, there is any possibility, by tuning ompi, the reduce operation syncrhonize all the ranks that are involved at the end of the operation? Also I would like to know if there is any mechanism to know at runtime which algorithm is being used. Thanks for all! - Fran
