DGETRS (3lapack)

solve a system of linear equations A * X = B or A' * X = B with a general N-by-N matrix A using the LU factorization computed by DGETRF

SYNOPSIS

  SUBROUTINE DGETRS( TRANS, N, NRHS, A, LDA, IPIV, B, LDB, INFO )

      CHARACTER      TRANS

      INTEGER        INFO, LDA, LDB, N, NRHS

      INTEGER        IPIV( * )

      DOUBLE         PRECISION A( LDA, * ), B( LDB, * )

PURPOSE

  DGETRS solves a system of linear equations
     A * X = B  or  A' * X = B with a general N-by-N matrix A using the LU
  factorization computed by DGETRF.

ARGUMENTS

  TRANS   (input) CHARACTER*1
          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.  N >= 0.

  NRHS    (input) INTEGER
          The number of right hand sides, i.e., the number of columns of the
          matrix B.  NRHS >= 0.

  A       (input) DOUBLE PRECISION array, dimension (LDA,N)
          The factors L and U from the factorization A = P*L*U as computed by
          DGETRF.

  LDA     (input) INTEGER
          The leading dimension of the array A.  LDA >= max(1,N).

  IPIV    (input) INTEGER array, dimension (N)
          The pivot indices from DGETRF; for 1<=i<=N, row i of the matrix was
          interchanged with row IPIV(i).

  B       (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
          On entry, the right hand side matrix B.  On exit, 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