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

NAME

dtrtrs - solve a triangular system of the form A * X = B or A**T * X = B,

SYNOPSIS

  SUBROUTINE DTRTRS( UPLO, TRANSA, DIAG, N, NRHS, A, LDA, B, LDB, 
 *      INFO)
  CHARACTER * 1 UPLO, TRANSA, DIAG
  INTEGER N, NRHS, LDA, LDB, INFO
  DOUBLE PRECISION A(LDA,*), B(LDB,*)

  SUBROUTINE DTRTRS_64( UPLO, TRANSA, DIAG, N, NRHS, A, LDA, B, LDB, 
 *      INFO)
  CHARACTER * 1 UPLO, TRANSA, DIAG
  INTEGER*8 N, NRHS, LDA, LDB, INFO
  DOUBLE PRECISION A(LDA,*), B(LDB,*)

F95 INTERFACE

  SUBROUTINE TRTRS( UPLO, [TRANSA], DIAG, [N], [NRHS], A, [LDA], B, 
 *       [LDB], [INFO])
  CHARACTER(LEN=1) :: UPLO, TRANSA, DIAG
  INTEGER :: N, NRHS, LDA, LDB, INFO
  REAL(8), DIMENSION(:,:) :: A, B

  SUBROUTINE TRTRS_64( UPLO, [TRANSA], DIAG, [N], [NRHS], A, [LDA], B, 
 *       [LDB], [INFO])
  CHARACTER(LEN=1) :: UPLO, TRANSA, DIAG
  INTEGER(8) :: N, NRHS, LDA, LDB, INFO
  REAL(8), DIMENSION(:,:) :: A, B

C INTERFACE

#include <sunperf.h>

void dtrtrs(char uplo, char transa, char diag, int n, int nrhs, double *a, int lda, double *b, int ldb, int *info);

void dtrtrs_64(char uplo, char transa, char diag, long n, long nrhs, double *a, long lda, double *b, long ldb, long *info);

PURPOSE

dtrtrs solves a triangular system of the form

where A is a triangular matrix of order N, and B is an N-by-NRHS matrix. A check is made to verify that A is nonsingular.

ARGUMENTS

• UPLO (input)
  

   = 'U':  A is upper triangular;

   = 'L':  A is lower triangular.

• TRANSA (input)
  Specifies the form of the system of equations:

   = 'N':  A * X  = B  (No transpose)

   = 'T':  A**T * X  = B  (Transpose)

   = 'C':  A**H * X  = B  (Conjugate transpose  = Transpose)

• DIAG (input)
  

   = 'N':  A is non-unit triangular;

   = 'U':  A is unit triangular.

• N (input)
  The order of the matrix A. N > = 0.

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

• A (input)
  The triangular matrix A. If UPLO = 'U', the leading N-by-N upper triangular part of the array A contains the upper triangular matrix, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading N-by-N lower triangular part of the array A contains the lower triangular matrix, and the strictly upper triangular part of A is not referenced. If DIAG = 'U', the diagonal elements of A are also not referenced and are assumed to be 1.

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

• B (input/output)
  On entry, the right hand side matrix B. On exit, if INFO = 0, the solution matrix X.

• LDB (input)
  The leading dimension of the array B. LDB > = max(1,N).

• INFO (output)
  

   = 0:  successful exit

   < 0: if INFO  = -i, the i-th argument had an illegal value

   > 0: if INFO  = i, the i-th diagonal element of A is zero,
  indicating that the matrix is singular and the solutions
  X have not been computed.