• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

dgetri - compute the inverse of a matrix using the LU factorization computed by SGETRF

SYNOPSIS

  SUBROUTINE DGETRI( N, A, LDA, IPIVOT, WORK, LDWORK, INFO)
  INTEGER N, LDA, LDWORK, INFO
  INTEGER IPIVOT(*)
  DOUBLE PRECISION A(LDA,*), WORK(*)

  SUBROUTINE DGETRI_64( N, A, LDA, IPIVOT, WORK, LDWORK, INFO)
  INTEGER*8 N, LDA, LDWORK, INFO
  INTEGER*8 IPIVOT(*)
  DOUBLE PRECISION A(LDA,*), WORK(*)

F95 INTERFACE

  SUBROUTINE GETRI( [N], A, [LDA], IPIVOT, [WORK], [LDWORK], [INFO])
  INTEGER :: N, LDA, LDWORK, INFO
  INTEGER, DIMENSION(:) :: IPIVOT
  REAL(8), DIMENSION(:) :: WORK
  REAL(8), DIMENSION(:,:) :: A

  SUBROUTINE GETRI_64( [N], A, [LDA], IPIVOT, [WORK], [LDWORK], [INFO])
  INTEGER(8) :: N, LDA, LDWORK, INFO
  INTEGER(8), DIMENSION(:) :: IPIVOT
  REAL(8), DIMENSION(:) :: WORK
  REAL(8), DIMENSION(:,:) :: A

C INTERFACE

#include <sunperf.h>

void dgetri(int n, double *a, int lda, int *ipivot, int *info);

void dgetri_64(long n, double *a, long lda, long *ipivot, long *info);

PURPOSE

dgetri 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)
  The order of the matrix A. N > = 0.

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

• IPIVOT (input)
  The pivot indices from SGETRF; for 1 < =i < =N, row i of the matrix was interchanged with row IPIVOT(i).

• WORK (workspace)
  On exit, if INFO =0, then WORK(1) returns the optimal LDWORK.

• LDWORK (input)
  The dimension of the array WORK. LDWORK > = max(1,N). For optimal performance LDWORK > = N*NB, where NB is the optimal blocksize returned by ILAENV.

  If LDWORK = -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 LDWORK is issued by XERBLA.

• INFO (output)
  

   = 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.