[Mpi-comments] MPI_Dims_create(..., ndims=0, ...) semantic ?

[Gilles Gouaillardet]

Folks,


Does the standard specifiy the behavior of MPI_Dims_create() when the 
ndims argument is zero ?


the standard only says negative input values of dims[i] are erroneous, 
but does not say anything about ndims.

ndims is the number of Cartesian dimensions (integer), and though a 
negative number likely looks erroneous

to most of us, a zero value is incorrect from a mathematical point of 
view (and i wish i remembered that ...)


Could someone tell me how a zero value should be interpreted ?

(e.g. valid/invalid/up to the implementor ?)


FWIW, currently

in MPICH, this is a no-op.

In Open MPI, this is an error by default, but if parameter check is 
manually disabled, then this is a no-op too.


Cheers,


Gilles

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