We recently upgraded our 64 bit Fortran compilers on Windows, OSX and linux to 15.0.1.148 Build 20141023. One of our nightly verification cases failed when using the Windows release compilation (/O2 /Qopenmp). The failure was substantial -- a totally spurious result. All other builds worked (linux, OSX, Windows debug). This is a very large computational fluids code broken up into about 30 source files. The code is fully compliant with Fortran 2003 and we run the thread checker on hundreds of test cases each day. The thread checker did not detect a problem, and we have run these test cases with previous versions from roughly 9 through 13. I tracked down the problem to one source file, which contained a single OpenMP construct. When I removed the OpenMP comments, but still compiled with /Qopenmp, the case still failed. When I compiled this one source file without the /Qopenmp, the case worked. I even got the case to work with OpenMP when I added a write statement to one of the loops -- a loop that was not parallelized with OpenMP. This leads me to suspect that there is a problem with the /O2 optimization (/O1 works fine) combined with /Qopenmp. It would be difficult to submit the entire code and test case, but can you think of something that might have changed in version 15 vis a vis OpenMP and optimization?
↧