ScaLAPACK global vs local parameters - fix some doc?

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ScaLAPACK global vs local parameters - fix some doc?

Postby dbakshee » Mon Feb 15, 2016 12:28 am


Perhaps all ScaLAPACK functions have their parameters marked as 'local' or 'global'. What these attributes mean, is not clearly articulated in the ScaLAPACK Users' Guide. To me 'global' means the parameter shall be the same in every process calling this synchronous parallel routine, so they synchronously describe a parallel global data or operation. For example the size of a distributed global matrix shall be the same in every process. On opposite, attribute 'local' means the parameter may have different value on different processes, for example, leading dimension of a local part of the global matrix, or a workspace buffer may be different between the processes. In most cases the matrices (input or output) should be local, because they do not contain the global matrix, only a part of the global distributed matrix. Most arrays, with notable exception of descriptors named DESC*, should also be local, especially if they are 'workspace' arrays. However, about 24 sources in ScaLAPACK refer to the piece of A as 'global', and other parameters questionably marked 'global'. Is this understanding correct? If so, fixing documentation will improve usability of ScaLAPACK.

I prepared a few patches showing what changes should be made to the sources, and I attach them here as a plaint text mailbox file just in case you may find them useful.

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