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

NAME

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

SYNOPSIS

  SUBROUTINE STBTRS( UPLO, TRANSA, DIAG, N, NDIAG, NRHS, A, LDA, B, 
 *      LDB, INFO)
  CHARACTER * 1 UPLO, TRANSA, DIAG
  INTEGER N, NDIAG, NRHS, LDA, LDB, INFO
  REAL A(LDA,*), B(LDB,*)

  SUBROUTINE STBTRS_64( UPLO, TRANSA, DIAG, N, NDIAG, NRHS, A, LDA, B, 
 *      LDB, INFO)
  CHARACTER * 1 UPLO, TRANSA, DIAG
  INTEGER*8 N, NDIAG, NRHS, LDA, LDB, INFO
  REAL A(LDA,*), B(LDB,*)

F95 INTERFACE

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

  SUBROUTINE TBTRS_64( UPLO, TRANSA, DIAG, [N], NDIAG, [NRHS], A, [LDA], 
 *       B, [LDB], [INFO])
  CHARACTER(LEN=1) :: UPLO, TRANSA, DIAG
  INTEGER(8) :: N, NDIAG, NRHS, LDA, LDB, INFO
  REAL, DIMENSION(:,:) :: A, B

C INTERFACE

#include <sunperf.h>

void stbtrs(char uplo, char transa, char diag, int n, int ndiag, int nrhs, float *a, int lda, float *b, int ldb, int *info);

void stbtrs_64(char uplo, char transa, char diag, long n, long ndiag, long nrhs, float *a, long lda, float *b, long ldb, long *info);

PURPOSE

stbtrs solves a triangular system of the form

where A is a triangular band 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 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.

• NDIAG (input)
  The number of superdiagonals or subdiagonals of the triangular band matrix A. NDIAG > = 0.

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

• A (input)
  The upper or lower triangular band matrix A, stored in the first kd+1 rows of A. The j-th column of A is stored in the j-th column of the array A as follows: if UPLO = 'U', A(kd+1+i-j,j) = A(i,j) for max(1,j-kd) < =i < =j; if UPLO = 'L', A(1+i-j,j) = A(i,j) for j < =i < =min(n,j+kd). If DIAG = 'U', the diagonal elements of A are not referenced and are assumed to be 1.

• LDA (input)
  The leading dimension of the array A. LDA > = NDIAG+1.

• 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.