Teuchos: initializeKokkos' use of call_once requires TPL_ENABLE_Pthread=ON for serial g++ builds

[kddevin]

@trilinos/teuchos @trilinos/tpetra

Expectations and Current behavior

Serial builds with g++ and TPL_ENABLE_Pthread=OFF used to work. Now, with gnu compilers and TPL_ENABLE_Pthread=OFF, I can build in serial but Teuchos' initializeKokkos throws an error.

It appears that g++ requires Pthread to correctly execute std::call_once, which is used in initializeKokkos. Thus, TPL_ENABLE_Pthread=OFF leads to an error.

The attached program demonstrates the std::call_once behavior. Here are the compilations and test results. I've seen the same behavior with gcc 4.9.3, 6.3.1 and 7.2.1.

callOnce.cpp.txt

g++ -std=c++11 callOnce.cpp
a.out
In initialize 0
terminate called after throwing an instance of 'std::system_error'
what(): Unknown error 18446744073709551615
Abort (core dumped)
g++ -std=c++11 -pthread callOnce.cpp
a.out
In initialize 0
In initializeOnce 0
In initialize 1
In initialize 2
In initialize 3
In initialize 4
In initialize 5
In initialize 6
In initialize 7
In initialize 8
In initialize 9
Done: callCnt = 10; initCnt = 1

Motivation and Context

Serial builds of Zoltan2 tests with TPL_ENABLE_Pthread=OFF build but do not execute.
Discovered trying to diagnose #3033

Definition of Done

Possible Solution

Can the use of call_once be safely removed, with initializeKokkos just testing Kokkos' initialization status? Or is call_once really needed for threading?

Steps to Reproduce

Build serial Zoltan2 with gnu compilers and -DTPL_ENABLE_Pthread=OFF; make test.

Your Environment

module purge
module load sems-env
module load sems-gcc/4.9.3
cmake
-DTPL_ENABLE_Pthread:BOOL=OFF
-DTrilinos_ENABLE_SECONDARY_TESTED_CODE:BOOL=ON
-DTrilinos_ENABLE_ALL_OPTIONAL_PACKAGES:BOOL=OFF
-DTrilinos_ENABLE_TESTS:BOOL=OFF
-DTrilinos_ENABLE_EXPLICIT_INSTANTIATION:BOOL=ON
-DTrilinos_ENABLE_Zoltan2:BOOL=ON
-DZoltan2_ENABLE_TESTS:BOOL=ON
..

Related Issues

#3033

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Additional Information

[mhoemmen]

I merged PR #3058 into develop. Hopefully that will fix this issue. Please let me know if you continue to have troubles; thanks!

[mhoemmen]

FYI, #3058 purges use of std::call_once from Tpetra::Map's initialization of Kokkos. If it later becomes necessary to reintroduce std::call_once, we should protect it with the macro corresponding to TPL_ENABLE_Pthread.