Bug fix: zero-length write request to a record variable in a collective put API - #239
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wkliao wants to merge 3 commits into
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Bug fix: zero-length write request to a record variable in a collective put API#239wkliao wants to merge 3 commits into
wkliao wants to merge 3 commits into
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varp is needed to tell if a variable is a record variable. With this change, varid must be valid when reaching to put_varm(). Another fix is required to return error earlier in dispatcher when a invalid varid is detected.
When writing to a record variable, a collective call to MPI_Allreduce() is necessary to update and sync-ed the number of records among all processes. For fix-sized variables, such a call to MPI_Allreduce() is not necessary. The argument varid of a put API supplied by the user may point to either a fix-sized or record variable. Because there is no way to tell if an invalid varid is a fix-sized variable or a record variable, there is no consistent if-condition can be devised to determine whether to call MPI_Allreduce(). The solution adopted by this commit adds a call to MPI_Allreduce() to check the error returned from sanity_check(), which unfortunately adds some communication cost. Luckily, this fix is only necessary for collective blocking put APIs.
…put API This test program, provided by Blaise Bourdin, calls a collective blocking put API to write to a record variable where one of the processes makes a zero-length request. When writing to a record variable, PnetCDF calls MPI_Allreduce to update and sync the number of records among all processes. If a subset of the processes has a zero-length request, these processes may not participate the call to MPI_Allreduce, causing program to hang. See PR Parallel-NetCDF#239.
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This PR fixes the issue reported in #238