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NAME DGTTRS - solve one of the systems of equations A*X = B or A'*X = B, SYNOPSIS SUBROUTINE DGTTRS( TRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB, INFO ) CHARACTER TRANS INTEGER INFO, LDB, N, NRHS INTEGER IPIV( * ) DOUBLE PRECISION B( LDB, * ), D( * ), DL( * ), DU( * ), DU2( * ) PURPOSE DGTTRS solves one of the systems of equations A*X = B or A'*X = B, with a tridiagonal matrix A using the LU factorization computed by DGTTRF. ARGUMENTS TRANS (input) CHARACTER Specifies the form of the system of equations: = 'N': A * X = B (No transpose) = 'T': A'* X = B (Transpose) = 'C': A'* X = B (Conjugate transpose = Transpose) N (input) INTEGER The order of the matrix A. NRHS (input) INTEGER The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0. DL (input) DOUBLE PRECISION array, dimension (N-1) The (n-1) multipliers that define the matrix L from the LU factorization of A. D (input) DOUBLE PRECISION array, dimension (N) The n diagonal elements of the upper triangular matrix U from the LU factorization of A. DU (input) DOUBLE PRECISION array, dimension (N-1) The (n-1) elements of the first superdiagonal of U. DU2 (input) DOUBLE PRECISION array, dimension (N-2) The (n-2) elements of the second superdiagonal of U. IPIV (input) INTEGER array, dimension (N) The pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i). IPIV(i) will always be either i or i+1; IPIV(i) = i indi- cates a row interchange was not required. (LDB,NRHS) B (input/output) DOUBLE PRECISION array, dimension On entry, the right hand side matrix B. On exit, B is overwritten by the solution matrix X. LDB (input) INTEGER The leading dimension of the array B. LDB >= max(1,N). INFO (output) INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value