On Sat, Apr 03, 2021 at 08:30:31PM -0700, Damian Rouson wrote: > Hi Steve, > > I hope the gfortran developers won't commit a patch that replaces > existing behavior with a stub that simply emits an error message.
The current behavior is incorrect with respect to the Fortran standard if one runs a compiled program multiple times. The patch fixes a bug. > It has been a while since I looked at the previous emails regarding > problems with the current behavior so I'm not expressing an opinion > about the current behavior. I'm simply advocating against breaking > existing codes that rely on the current behavior if nothing better is > being provided. It cannot be helped. The underlying coarray implementation must handle RANDOM_INIT(). AFAICT, there must be communication between images if RANDOM_INIT() is used. libgfortran is not compiled with -fcoarray=lib (or -fcoarray=shared), so the coarray implementation(s) must deal with RANDOM_INIT(). > Or as a compromise, would you mind changing the patch so that the > error message is emitted only in the problematic cases? You presented > one problematic case out of the four possible combinations of > RANDOM_INIT() arguments. With only four possible combinations to > enumerate, I hope this suggestion isn't burdensome. Consider, read(*,*) repeatable, image_distinct call random_init(repeatable, image_distinct) for -fcoarray=none or -fcoarray=single, the image_distinct argument is irrevelant. This is simply translated to _gfortran_random_init(repeatable, image_distinct) For -fcoarray=lib (and by extension OpenCoarray), a simple 1 line patch on top of my patch would generate _gfortran_caf_random_init(repeatable, image_distinct) where is it assumed the function is coarray aware. Similarly, if -fcoarray=shared, then a 1 line patch would generate _gfortran_cas_random_init(repeatable, image_distinct) where is it assumed the function is coarray aware. There are 4 cases: (1) repeatable=.true., image_distinct=.true. (2) repeatable=.true., image_distinct=.false. (3) repeatable=.false., image_distinct=.true. (4) repeatable=.false., image_distinct=.false. IIRC, cases (1)-(3) don't require communication. case (4) does. That is, case (4) requires the same set of random seeds to be used on all images. > Regarding "someone who cares about coarray Fortran," finding people to > work on such an effort is quite challenging. Finding people willing to work on gfortran is as challenging if not more so. A year ago, I posted in c.l.f a list of 20+ PRs with patches that I had created. I don't do git. It would take someone with git-fu little time to take my patches and apply them to a source tree. Testing was done by me, but I would encourage git-fu aware individuals to bootstrap and test the patches. Then commit the patch. Harald has stepped up and grabbed a few. TO BE CLEAR, I AM NOT RANTING AT THE PEOPLE WHO HAVE CONTRIBUTED AND MAINTAINED GFORTRAN FOR YEARS. gfortran needs new blood, or it is destined for the bit bucket. > I believe Andre > Verheschild has some limited availability so I'm cc'ing him and will > discuss it with him if he's interested. If you know others who might > be interested, please let us know. Don't know any new people who are interested in gfortran. -- Steve
