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* [Bug libgomp/94290] New: [gfortran] OpenMP target teams distribute default firstprivate causes failure to map back values from device @ 2020-03-23 18:47 jhdavis at udel dot edu 2020-03-27 19:32 ` [Bug libgomp/94290] " jakub at gcc dot gnu.org 0 siblings, 1 reply; 2+ messages in thread From: jhdavis at udel dot edu @ 2020-03-23 18:47 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94290 Bug ID: 94290 Summary: [gfortran] OpenMP target teams distribute default firstprivate causes failure to map back values from device Product: gcc Version: 9.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libgomp Assignee: unassigned at gcc dot gnu.org Reporter: jhdavis at udel dot edu CC: jakub at gcc dot gnu.org Target Milestone: --- Created attachment 48099 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48099&action=edit Target teams distribute default(firstprivate) reproducible Hello, This bug report is from the SOLLVE team regarding default(firstprivate) in an offloading construct. --- SUMMARY --- On a target teams distribute clause the default(firstprivate) clause we are seeing a failure to map back changes made on the device. In the attached reproducible we test both the 'private' and 'first' aspects of the clause for both scalars and arrays on the device and then check the results on the host. Changing the default(firstprivate) in both parts of the test to firstprivate(privatized, privatized_array) causes the test to work as expected. The version of the test in our suite is availible here: https://github.com/SOLLVE/sollve_vv/blob/d031050b40edf3cd261219d649e932b4f4743ff6/tests/4.5/target_teams_distribute/test_target_teams_distribute_default_firstprivate.F90 --- DETAILS --- gfortran version: 9.2.0 System: x86_64-pc-linux-gnu (Summit) Config options: ../gcc9.2/configure --enable-offload-targets=nvptx-none --with-cuda-driver-include=/software/apps/cuda/9.2//include --with-cuda-driver-lib=/software/apps/cuda/9.2//lib64 --disable-bootstrap --disable-multilib --enable-languages=c,c++,fortran,lto --prefix=/software/apps/gcc/9.2 No compiler output. Runtime output: test_firstprivate_private gave 1024 expected 0 test_firstprivate_first gave 1024 expected 0 Command line to trigger bug: gfortran -fopenmp -ffree-line-length-none default_firstprivate_bug.F90 -o default_firstprivate_bug.F90.o ./default_firstprivate_bug.F90.o Best, Josh Davis ^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug libgomp/94290] [gfortran] OpenMP target teams distribute default firstprivate causes failure to map back values from device 2020-03-23 18:47 [Bug libgomp/94290] New: [gfortran] OpenMP target teams distribute default firstprivate causes failure to map back values from device jhdavis at udel dot edu @ 2020-03-27 19:32 ` jakub at gcc dot gnu.org 0 siblings, 0 replies; 2+ messages in thread From: jakub at gcc dot gnu.org @ 2020-03-27 19:32 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94290 Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |INVALID Status|UNCONFIRMED |RESOLVED --- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> --- This is a test bug. Please see https://www.openmp.org/spec-html/5.0/openmpse22.html#x116-4340002.14 When you have a combined or composite constructs, clauses that apply to just one of the constructs generally are applied to the construct which allows them, while clauses that can be applied to multiple constructs have more complicated clause distribution rules in that section. When you have combined !$omp target teams default(firstprivate) map(from:a) then the default clause, as it applies to teams only and not target, goes to teams, and map clauses go to target. So, it is like !$omp target map(from:a) !$omp teams default(firstprivate) Now, if you reference a in the teams region, there is no data sharing clause on the teams construct for a, and the default is firstprivate, which means an implicit firstprivate(a) clause is added to the teams construct. The target construct has a map clause, so a on that construct is mapped rather than privatized, which means that each team will have its own privatized copy of a, and the uninitialized original mapped a is then copied back. Either don't use default(firstprivate) on the combined constructs because you really want sharing for those vars, or you can use !$omp target teams default(firstprivate) map(from:a) shared(a) While OpenMP has a restriction that the same list item can't be specified in mapping and data sharing clauses, my understanding is that this applies after the clauses are distributed among the constituent constructs, and as target construct doesn't allow shared clause and teams construct doesn't allow map clause, each goes to one of them and should do what you want. Adding shared(a, b, c, d) clause to both combined directives in your testcase fixes it. You can even just add shared(d), though in that case the a, b, c arrays are mapped to the device and then copied from that to each of the teams private copies. ^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2020-03-27 19:32 UTC | newest] Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-03-23 18:47 [Bug libgomp/94290] New: [gfortran] OpenMP target teams distribute default firstprivate causes failure to map back values from device jhdavis at udel dot edu 2020-03-27 19:32 ` [Bug libgomp/94290] " jakub at gcc dot gnu.org
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