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

NAME

cgetri - compute the inverse of a matrix using the LU factorization computed by CGETRF

SYNOPSIS

  SUBROUTINE CGETRI( N, A, LDA, IPIVOT, WORK, LDWORK, INFO)
  COMPLEX A(LDA,*), WORK(*)
  INTEGER N, LDA, LDWORK, INFO
  INTEGER IPIVOT(*)

  SUBROUTINE CGETRI_64( N, A, LDA, IPIVOT, WORK, LDWORK, INFO)
  COMPLEX A(LDA,*), WORK(*)
  INTEGER*8 N, LDA, LDWORK, INFO
  INTEGER*8 IPIVOT(*)

F95 INTERFACE

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

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

C INTERFACE

#include <sunperf.h>

void cgetri(int n, complex *a, int lda, int *ipivot, int *info);

void cgetri_64(long n, complex *a, long lda, long *ipivot, long *info);

PURPOSE

cgetri computes the inverse of a matrix using the LU factorization computed by CGETRF.

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 CGETRF. 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 CGETRF; 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.