(i) The remap options are only used in multi-gang mode; the custom remap is provided for cases where the ScaLAPACK remap function (pdgemr2d) performs poorly or fails.
(ii) The busy-work exponent, BWEXP, sets the amount of busy-work done as a function of the IO data size. For N data elements written/read the busy-work function will perform NBWEXP floating-point operations.
If the IO data are thought of as matrices, as in the parent application, then
BWEXP = 1.0 corresponds to level 2 BLAS
BWEXP = 1.5 corresponds to level 3 BLAS
If the IO data are thought of as vectors then
BWEXP = 1.0 corresponds to level 1 BLAS
BWEXP = 2.0 corresponds to level 2 BLAS