Array Layout Guidelines

Two-Dimensional Arrays: If a and b are two-dimensional, S3L_gen_band_solve is more efficient when axis_r = 0, axis_d = 1, array a is block distributed along axis 1, axis_row = 0, axis_col = 1 and array b is block distributed along axis 0.

Note that the values cited in the previous paragraph apply to programs using the C/C++ interface--that is, they assume zero-based array indexing. When S3L_gen_band_solve is called from F77 or F90 applications, these values must be increased by one. Therefore, when a and b are two-dimensional and S3L_gen_band_solve is called by a Fortran program, the solver is more efficient when axis_r = 1, axis_d = 2, array a is block distributed along axis 2, axis_row = 1, axis_col = 2 and array b is block distributed along axis 1.

When a and b are two-dimensional and nrhs is greater than 1, the size of a must be such that n is divisible by the number of processors.

Arrays With More Than Two Dimensions: If a and b have more than two dimensions, S3L_gen_band_solve is more efficient when axes axis_r and axis_d of a and axes axis_row and axis_col are local (not distributed).