Simplified Quasi-Minimal Residual Algorithm

Simplified Quasi-Minimal Residual (SQMR) algorithm for the solution of linear systems with with squa

This function solves the system of linear equations A*x=b, using the simplest form of the SQMR algorithm without look-ahead, where A is square and symmetric.

SQMR is an adaptation of the general nonsymmetric QMR method to exploit the symmetry of the matrix A. With SQMR, one can use symmetric indefinite preconditioners for symmetric but indefinite systems, while SYMMLQ and MINRES require symmetric positive-definite preconditioners.