sgetri.f

来自「基于Blas CLapck的.用过的人知道是干啥的」· F 代码 · 共 103 行

      SUBROUTINE SGETRI( N, A, LDA, IPIV, WORK, LWORK, INFO )
*
*  -- LAPACK routine (version 3.0) --
*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
*     Courant Institute, Argonne National Lab, and Rice University
*     June 30, 1999
*
*  -- Modified by R. Clint Whaley for ATLAS Fortran77 LAPACK interface,
*     2001
*
*
*     .. Scalar Arguments ..
      INTEGER            INFO, LDA, LWORK, N
*     ..
*     .. Array Arguments ..
      INTEGER            IPIV( * )
      REAL A( LDA, * ), WORK( * )
*     ..
*
*  Purpose
*  =======
*
*  SGETRI computes the inverse of a matrix using the LU factorization
*  computed by SGETRF.
*
*  This method inverts U and then computes inv(A) by solving the system
*  inv(A)*L = inv(U) for inv(A).
*
*  Arguments
*  =========
*
*  N       (input) INTEGER
*          The order of the matrix A.  N >= 0.
*
*  A       (input/output) REAL array, dimension (LDA,N)
*          On entry, the factors L and U from the factorization
*          A = P*L*U as computed by SGETRF.
*          On exit, if INFO = 0, the inverse of the original matrix A.
*
*  LDA     (input) INTEGER
*          The leading dimension of the array A.  LDA >= max(1,N).
*
*  IPIV    (input) INTEGER array, dimension (N)
*          The pivot indices from ZGETRF; for 1<=i<=N, row i of the
*          matrix was interchanged with row IPIV(i).
*
*  WORK    (workspace/output) REAL array, dimension (LWORK)
*          On exit, if INFO=0, then WORK(1) returns the optimal LWORK.
*
*  LWORK   (input) INTEGER
*          The dimension of the array WORK.  LWORK >= max(1,N).
*          For optimal performance LWORK >= N*NB, where NB is
*          the optimal blocksize returned by ILAENV.
*
*          If LWORK = -1, then a workspace query is assumed; the routine
*          only calculates the optimal size of the WORK array, returns
*          this value as the first entry of the WORK array, and no error
*          message related to LWORK is issued by XERBLA.
*
*  INFO    (output) INTEGER
*          = 0:  successful exit
*          < 0:  if INFO = -i, the i-th argument had an illegal value
*          > 0:  if INFO = i, U(i,i) is exactly zero; the matrix is
*                singular and its inverse could not be computed.
*
*  =====================================================================
*
*     ..
*     .. Local Scalars ..
      LOGICAL            LQUERY
*     ..
*     .. External Subroutines ..
      EXTERNAL           XERBLA, ATL_F77WRAP_SGETRI
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          MAX
*     ..
*     .. Executable Statements ..
*
*     Test the input parameters.
*
      INFO = 0
      LQUERY = ( LWORK.EQ.-1 )
      IF( N.LT.0 ) THEN
         INFO = -1
      ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
         INFO = -3
      ELSE IF( LWORK.LT.MAX( 1, N ) .AND. .NOT.LQUERY ) THEN
         INFO = -6
      END IF
      IF( INFO.NE.0 ) THEN
         CALL XERBLA( 'SGETRI', -INFO )
         RETURN
      END IF
*
      CALL ATL_F77WRAP_SGETRI(N, A, LDA, IPIV, WORK, LWORK, INFO)
*
      RETURN
*
*     End of SGETRI
*
      END