v6.1.2 (Dec 31, 2021)

Version 6.1.2, Dec 31, 2021

* performance: revised swap_rule in GrB_mxm, which decides whether
    to compute C=A*B or C=(B'*A')', and variants, resulting in up
    to 3x performance gain over v6.1.1 for GrB_mxm (observed;
    could be higher in other cases).