NAME dstsv - compute the solution to a system of linear equations A * X = B where A is a symmetric tridiagonal matrix SYNOPSIS SUBROUTINE DSTSV( N, L, D, SUBL, IPIV, INFO ) INTEGER INFO, N DOUBLE PRECISION D( * ) DOUBLE PRECISION L( * ), SUBL( * ) #include <sunperf.h> void dstsv(int n, double *l, double *d, double *subl, int *info) ; PURPOSE DSTSV computes the solution to a system of linear equations A * X = B where A is a symmetric tridiagonal matrix. ARGUMENTS N (input) INTEGER The order of the matrix A. N >= 0. L (input/output) DOUBLE PRECISION array, dimension (N) On entry, the n-1 subdiagonal elements of the tri- diagonal matrix A. On exit, part of the factori- zation of A. D (input/output) DOUBLE PRECISION array, dimension (N) On entry, the n diagonal elements of the tridiago- nal matrix A. On exit, the n diagonal elements of the diagonal matrix D from the factorization of A. SUBL (output) DOUBLE PRECISION array, dimension (N) On exit, part of the factorization of A. IPIV (output) INTEGER array, dimension (N) On exit, the pivot indices of the factorization. INFO (output) INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an ille- gal value > 0: if INFO = i, D(k,k) is exactly zero. The factorization has been completed, but the block diagonal matrix D is exactly singular and division by zero will occur if it is used to solve a system of equations.
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