## Version 1.1.0

This routine ﬁnds an approximate inverse $M$ of an $n×n$ sparse unsymmetric matrix $A$ by attempting to minimize the diﬀerence between $AM$ and the identity matrix in the Frobenius norm. The process may be improved by ﬁrst performing a block triangularization of $A$ and then ﬁnding approximate inverses to the resulting diagonal blocks.
$y=Mz\phantom{\rule{2em}{0ex}}and\phantom{\rule{2em}{0ex}}y={M}^{T}z.$
The principal use of such an approximate inverse is likely to be in preconditioning iterative methods for solving the linear system $Ax=b$.