The four existing stable factorization methods for symmetric indefinite pivoting (row or column exchanges) maintains a band structure in the reduced matrix and the factors, but destroys symmetry completely once an off-diagonal pivot is used. Two-by-two block pivoting maintains symmetry at all times, but quickly destroys the band structure. Gaussian reduction to tridiagonal also maintains symmet...

We combine the idea of the direct LU factorization with the idea of the pivoting strategy in the usual Gaussian elimination and show that two so-called total scaled and total pivoting strategies can be employed in addition to the traditional pivoting strategies: partial scaled, partial, and direct diagonal. In this paper we o er a general LU factorization with total scaled pivoting algorithm fr...

LAPACK and LINPACK both solve symmetric indeenite linear systems using the diagonal pivoting method with the partial pivoting strategy of Bunch and Kaufman (1977). No proof of the stability of this method has appeared in the literature. It is tempting to argue that the diagonal pivoting method is stable for a given pivoting strategy if the growth factor is small. We show that this argument is f...

LAPACK and LINPACK both solve symmetric indefinite linear systems using the diagonal pivoting method with the partial pivoting strategy of Bunch and Kaufman [Math. Comp., 31 (1977), pp. 163–179]. No proof of the stability of this method has appeared in the literature. It is tempting to argue that the diagonal pivoting method is stable for a given pivoting strategy if the growth factor is small....

Gaussian elimination is a canonical linear algebra procedure for solving linear systems of equations. In the last few years, the algorithm received a lot of attention in an attempt to improve its parallel performance. This article surveys recent developments in parallel implementations of the Gaussian elimination. Five different flavors are investigated. Three of them are based on different str...

This paper illustrates how the communication due to pivoting in the solution of symmetric indefinite linear systems can be reduced by considering innovative approaches that are different from pivoting strategies implemented in current linear algebra libraries. First a tiled algorithm where pivoting is performed within a tile is described and then an alternative to pivoting is proposed. The latt...

LAPACK and LINPACK both solve symmetric inde nite linear systems using the diagonal pivoting method with the partial pivoting strategy of Bunch and Kaufman (1977). No proof of the stability of this method has appeared in the literature. It is tempting to argue that the diagonal pivoting method is stable for a given pivoting strategy if the growth factor is small. We show that this argument is f...

LAPACK and LINPACK both solve symmetric indeenite linear systems using the diagonal pivoting method with the partial pivoting strategy of Bunch and Kaufman (1977). No proof of the stability of this method has appeared in the literature. It is tempting to argue that the diagonal pivoting method is stable for a given pivoting strategy if the growth factor is small. We show that this argument is f...