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Advanced multi threading support in CH4
Hajime Fujita edited this page Nov 9, 2018
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MPICH 3.3rc1 (released on 11/9/2018) introduced several improvements to MPI_THREAD_MULTIPLE. As of 3.3rc1, this feature is not enabled by default, therefore a special build configuration is needed.
Note that this feature is still in active development and some code that runs with CH3 or regular CH4 may not run correctly with this configuration.
The new improvements are implemented inside the CH4 device. So CH4 needs to be selected when building MPICH.
Example configure lines:
./configure --with-device=ch4:ofi --with-libfabric=<path/to/ofi/install>
./configure --with-device=ch4:ucx --with-ucx=<path/to/ucx/install>
Refer to MPICH README for more details on how to build CH4.
3.3rc1 introduced two threading models.
- Trylock-enqueue (
trylock) - Handoff (
handoff)
Build time configurations:
--enable-thread-cs=per-vni --enable-izem=queue --with-zm-prefix=yes --enable-ch4-mt=trylock --with-hwloc=<path/to/hwlocinstall>
Runtime configurations:
- None needed
Build time configurations:
--enable-thread-cs=per-vni --enable-izem=queue --with-zm-prefix=yes --enable-ch4-mt=handoff --with-hwloc=<path/to/hwlocinstall>
Runtime configurations:
- Set the environment variable:
MPIR_CVAR_ASYNC_PROGRESS=1