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| -rw-r--r-- | lib/spack/docs/basic_usage.rst | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/lib/spack/docs/basic_usage.rst b/lib/spack/docs/basic_usage.rst index ae591920db..1118160adf 100644 --- a/lib/spack/docs/basic_usage.rst +++ b/lib/spack/docs/basic_usage.rst @@ -436,6 +436,35 @@ package, e.g. if an application needs MPI-2 functions, it can depend on ``mpi@2:`` to indicate that it needs some implementation that provides MPI-2 functions. + +Constraining virtual packages +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +When installing a package that depends on a virtual package, you can +opt to specify the particular provider you want to use, or you can let +Spack pick. For example, if you just type this:: + + spack install mpileaks + +Then spack will pick a provider for you according to site policies. +If you really want a particular version, say mpich, then you could +run this instead:: + + spack install mpileaks ^mpich + +This forces spack to use some version of ``mpich`` for its +implementation. As always, you can be even more specific and require +a particular ``mpich`` version:: + + spack install mpileaks ^mpich@3 + +In this case, ``mpileaks`` only needs MPI-1 commands, so any MPI +implementation will do. If another package depends on ``mpi@2`` and +you try to give it an insufficient MPI implementation (e.g., one that +provides only ``mpi@:1``), then Spack will raise an error. Likewise, +if you try to plug in some package that doesn't provide MPI, Spack +will raise an error. + ``spack providers`` ~~~~~~~~~~~~~~~~~~~~~~~~~~ |