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

Chapter 13 Sparse Linear Equations 905
One-call usage DSLEFS
purpose of forming columns with identical structure to
increase the efficiency of the factorization. If
maxzer = 0, no additional fill is allowed. If many
solution vectors are to be computed for each
factorization, it is suggested that maxzer = 0 be used. If
only a few solution vectors are to be computed maxzer
= 10 could be tried but maxzer = 0 is perfectly
acceptable. Using values greater than 50 probably
increases the factorization time.
pvttol Pivoting tolerance; 0 ≤ pvttol ≤ 1. The value 0 gives a
reordering that minimizes fill; this value is appropriate
for positive definite matrices and provides the greatest
efficiency. The value 1 gives the best guarantee of
numerical stability for problems not known to be
positive definite.
msglvl Message level for printable output. Options:
msglvl ≤ 0 Suppress all output.
msglvl = 1 Error messages and summary
statistics.
msglvl = 2 More complete statistics.
msglvl = 3 First stage of debugging output.
msglvl = 4 Complete debugging output.
output Fortran logical unit number to which all printable
output is written.
colstr colstr(j) gives the index in rowind of the first nonzero
in the lower triangular part of column j of the matrix.
All of the nonzeros for column j are found, in ascending
order, in rowind(colstr(j)), rowind(colstr(j)+1), ...,
rowind(colstr(j+1)−1).
colstr(neqns+1) must be set to one greater than the
total number of nonzeros, nnzero, in the lower
triangular part of the matrix.
rowind List of row indices for all nonzeros, in ascending order
within each column, in the lower triangle part of the
matrix A.
value List of values corresponding in position to the indices
in rowind.
nrhs Number of right-hand sides.