HP MLIB User's Guide Vol. 2 7th Ed.

774 HP MLIB LAPACK User’s Guide
pdgssvx/ pzgssvx, pdgssvx_ABglobal/pzgssvx_ABglobal Solve systems of linear equations
But not options->ColPerm, whose value is ignored. This is because the
previous column permutation from ScalePermstruct->perm_c is used as
input. The user must also supply:
• A, the input matrix
• ScalePermstruct->perm_c, the column permutation.
• LUstruct->etree, the elimination tree.
The outputs returned include:
• A, the input matrix A overwritten by the scaled an permuted matrix
as described above.
• ScalePermstruct->perm_c, modified to describe how the input matrix
A was equilibrated and row permuted.
• LUstruct, modified to contain the new L and U factors.
4. The third value of options->Fact assumes that a matrix B with the same
sparsity pattern as A has already been factored, and where the row
permutation of B can be reused for A. This is useful when A and B have
similar numberical values, so that the same row permutation will make
both factorizations numerically stable. This lets us reuse all of the
previously computed structure of L and U.
• options->Fact = SamePattern_SameRowPerm: A is factored, assuming
not only the same nonzero pattern as the previously factored matrix B,
but reusing Bs row permutation.
In this case the user must still specify the following options as before:
• options->Equil
• options->ReplaceTinyPivot
But not options->RowPerm or options->ColPerm, whose values are
ignored. This is because the permutations from
ScalePermstruct->perm_r and ScalePermstruct->perm_c are used as
input.
The user must also supply:
• A, the input matrix
• ScalePermstruct->DiagScale, how the previous matrix was row
and/or column scaled.
• ScalePermstruct->R, the row scalings of the previous matrix, if any.
• ScalePermstruct->C, the columns scalings of the previous matrix, if
any.
• ScalePermstruct->perm_r, the row permutation of the previous
matrix.