Previously, we reported a possible Scalapack bug in the PZUNGQR function
That issue has still not been resolved, but it was stated that it was an issue with zero-sized matrices on some nodes. However, we have encountered a somewhat similar issue with PZUNGQR even when the local matrices do no have zero-size. In the attached test case, the PZGEMM call that follows the PZUNGQR call will either hang or produce Irecv error even though the QR matrices and the PZGEMM matrices have non-zero sized matrices on all nodes. Interestingly, if the matrices used in the PZGEMM call have a global size less than the block size (only one node has non-zero sized matrices), then it completes fine.
In the attached test case, the bug only occurs if single-node matrices call ZUNQGR and multiple node matrices call PZUNGQR. If all nodes call PZUNGQR it does not occur. However, in our full code the bug seems to occur sometimes even if all nodes call PZUNGQR. Unfortunately, I was not able to reduce this particular behavior down to a simple test case.