Specifies the parameter to be returned as the value of
= 1: the optimal blocksize; if this value is 1, an unblocked algorithm will give the best performance (unlikely).
= 2: the minimum block size for which the block routine should be used; if the usable block size is less than this value, an unblocked routine should be used.
= 3: the crossover point (in a block routine, for N less than this value, an unblocked routine should be used).
= 4: the number of shifts, used in the nonsymmetric eigenvalue routines (DEPRECATED).
= 5: the minimum column dimension for blocking to be used; rectangular blocks must have dimension at least
is given by
= 6: the crossover point for the SVD (when reducing an
matrix to bidiagonal form, if max(
) exceeds this value, a QR factorization is used first to reduce the matrix to a triangular form).
= 7: the number of processors.
= 8: the crossover point for the multishift QR method for nonsymmetric eigenvalue problems (DEPRECATED).
= 9: maximum size of the subproblems at the bottom of the computation tree in the divide-and-conquer algorithm (used by
=10: IEEE NaN arithmetic can be trusted not to trap.
=11: infinity arithmetic can be trusted not to trap.
or one of its subroutines, see
for detailed explanation.
(not all), as follows:
=17: maximum number of concurrent computational windows;
=18: number of eigenvalues/bulges in each window;
=19: computational window size;
=20: minimal percentage of FLOPS required for performing matrix-matrix multiplications instead of pipelined orthogonal transformations;
=21: width of block column slabs for row-wise application of pipelined orthogonal transformations in their factorized form;
=22: the maximum number of eigenvalues moved together over a process border;
=23: the number of processors involved in Aggressive Early Deflation (AED);
=99: Maximum iteration chunksize in OpenMP parallelization.