dtptri - compute the inverse of a real upper or lower triangular matrix A stored in packed format
SUBROUTINE DTPTRI(UPLO, DIAG, N, A, INFO) CHARACTER*1 UPLO, DIAG INTEGER N, INFO DOUBLE PRECISION A(*) SUBROUTINE DTPTRI_64(UPLO, DIAG, N, A, INFO) CHARACTER*1 UPLO, DIAG INTEGER*8 N, INFO DOUBLE PRECISION A(*) F95 INTERFACE SUBROUTINE TPTRI(UPLO, DIAG, N, A, INFO) CHARACTER(LEN=1) :: UPLO, DIAG INTEGER :: N, INFO REAL(8), DIMENSION(:) :: A SUBROUTINE TPTRI_64(UPLO, DIAG, N, A, INFO) CHARACTER(LEN=1) :: UPLO, DIAG INTEGER(8) :: N, INFO REAL(8), DIMENSION(:) :: A C INTERFACE #include <sunperf.h> void dtptri(char uplo, char diag, int n, double *a, int *info); void dtptri_64(char uplo, char diag, long n, double *a, long *info);
Oracle Solaris Studio Performance Library dtptri(3P) NAME dtptri - compute the inverse of a real upper or lower triangular matrix A stored in packed format SYNOPSIS SUBROUTINE DTPTRI(UPLO, DIAG, N, A, INFO) CHARACTER*1 UPLO, DIAG INTEGER N, INFO DOUBLE PRECISION A(*) SUBROUTINE DTPTRI_64(UPLO, DIAG, N, A, INFO) CHARACTER*1 UPLO, DIAG INTEGER*8 N, INFO DOUBLE PRECISION A(*) F95 INTERFACE SUBROUTINE TPTRI(UPLO, DIAG, N, A, INFO) CHARACTER(LEN=1) :: UPLO, DIAG INTEGER :: N, INFO REAL(8), DIMENSION(:) :: A SUBROUTINE TPTRI_64(UPLO, DIAG, N, A, INFO) CHARACTER(LEN=1) :: UPLO, DIAG INTEGER(8) :: N, INFO REAL(8), DIMENSION(:) :: A C INTERFACE #include <sunperf.h> void dtptri(char uplo, char diag, int n, double *a, int *info); void dtptri_64(char uplo, char diag, long n, double *a, long *info); PURPOSE dtptri computes the inverse of a real upper or lower triangular matrix A stored in packed format. ARGUMENTS UPLO (input) = 'U': A is upper triangular; = 'L': A is lower triangular. DIAG (input) = 'N': A is non-unit triangular; = 'U': A is unit triangular. N (input) The order of the matrix A. N >= 0. A (input/output) DOUBLE PRECISION array, dimension (N*(N+1)/2) On entry, the upper or lower triangular matrix A, stored columnwise in a linear array. The j-th column of A is stored in the array A as follows: if UPLO = 'U', A(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', A(i + (j-1)*((2*n-j)/2) = A(i,j) for j<=i<=n. See below for further details. On exit, the (triangular) inverse of the original matrix, in the same packed storage format. INFO (output) = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, A(i,i) is exactly zero. The triangular matrix is singular and its inverse can not be computed. FURTHER DETAILS A triangular matrix A can be transferred to packed storage using one of the following program segments: UPLO = 'U': UPLO = 'L': JC = 1 JC = 1 DO 2 J = 1, N DO 2 J = 1, N DO 1 I = 1, J DO 1 I = J, N A(JC+I-1) = A(I,J) A(JC+I-J) = A(I,J) 1 CONTINUE 1 CONTINUE JC = JC + J JC = JC + N - J + 1 2 CONTINUE 2 CONTINUE 7 Nov 2015 dtptri(3P)