- // Bareiss (fraction-free) elimination is generally a good guess:
- algo = solve_algo::bareiss;
- // For row<3, Bareiss elimination is equivalent to division free
- // elimination but has more logistic overhead
- if (row<3)
- algo = solve_algo::divfree;
- // This overrides any prior decisions.
- if (numeric_flag)
- algo = solve_algo::gauss;
+ unsigned density = 0;
+ for (const auto & r : m) {
+ density += !r.is_zero();
+ }
+ unsigned ncells = col*row;
+ if (numeric_flag) {
+ // For numerical matrices Gauss is good, but Markowitz becomes
+ // better for large sparse matrices.
+ if ((ncells > 200) && (density < ncells/2)) {
+ algo = solve_algo::markowitz;
+ } else {
+ algo = solve_algo::gauss;
+ }
+ } else {
+ // For symbolic matrices Markowitz is good, but Bareiss/Divfree
+ // is better for small and dense matrices.
+ if ((ncells < 120) && (density*5 > ncells*3)) {
+ if (ncells <= 12) {
+ algo = solve_algo::divfree;
+ } else {
+ algo = solve_algo::bareiss;
+ }
+ } else {
+ algo = solve_algo::markowitz;
+ }
+ }