| Issue |
53154
|
| Summary |
OpenMP target: `omp_pteam_mem_alloc` leaves variable thread-private
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
jkelling
|
To my understanding of OpenMP 5.0 2.11.2 (page 154, lines 4-6) a variable declared inside a `parallel` region within a `teams` region should become shared between all threads executing that parallel region when using the following `omp allocate` construct with the `omp_pteam_mem_alloc` allocator:
```c++
#pragma omp allocate(varName) allocator(omp_pteam_mem_alloc)
```
Using the current Clan Main (95a436f8cca6991dc0f30588d9b1af3223818168) this test fails:
```c++
#include <iostream>
#include <cstdio>
#include <omp.h>
int main()
{
int maxThreads = omp_get_max_threads();
constexpr int numTeams = 4;
int aLocal[numTeams];
int aTeam[numTeams];
std::cout << "maxThreads=" << maxThreads
<< "\tnumTeams=" << numTeams << std::endl;
#pragma omp target data map(tofrom:aLocal,aTeam)
#pragma omp target
{
#pragma omp teams num_teams(numTeams) thread_limit(maxThreads)
{
#pragma omp distribute
for(int t = 0; t < omp_get_num_teams(); ++t)
{
int team = 0;
#pragma omp parallel //num_threads(maxThreads)
{
int local = 0;
#pragma omp allocate(local) allocator(omp_pteam_mem_alloc)
#pragma omp atomic update
local += t+1;
#pragma omp atomic update
team += t+1;
#pragma omp barrier
// printf("TEAM %d, THREAD=%d, local=%d, team=%d\n"
// , (int)(omp_get_team_num()), (int)(omp_get_thread_num()), local, team);
if(omp_get_thread_num() == 0)
aLocal[t] = local;
}
aTeam[t] = team;
}
}
}
bool good = true;
for(int a = 0; a < numTeams; ++a)
{
if(aLocal[a] != aTeam[a])
{
std::cerr << "allocator(omp_pteam_mem_alloc) not shared in team for team " << a << ": "
<< aLocal[a] << " != " << aTeam[a] << '\n';
good = false;
}
}
return !good;
}
```
([on github](https://github.com/jkelling/omp5tests/blob/master/allocate/allocate.cpp))
* `CXXFLAGS=-"fopenmp -fopenmp=libomp -fopenmp-targets=x86_64-pc-linux-gnu -Wall -pedantic -Wopenmp-target -fopenmp=libomp -g -fopenmp"`
This shows, that the variable `local` remains private to each thread. Declaring `local` as `static` makes it shared in the whole target region (between all teams). In either case the `allocate` construct has no effect.
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