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template<typename T>
void trtrs(char *uplo, char *trans, char *diag, integer *n, integer *nrhs, T *a, integer *lda, T *b, integer *ldb, integer *info)# TRTRS solves a triangular system of the form A * X = B or A**T * X = B.
Purpose:
TRTRS solves a triangular system of the form A * X = B or A**T * X = B, 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.
- Parameters:
UPLO – [in]
UPLO is CHARACTER*1
= ‘U’: A is upper triangular;
= ‘L’: A is lower triangular.TRANS – [in]
TRANS is CHARACTER*1
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 – [in]
DIAG is CHARACTER*1
= ‘N’: A is non-unit triangular;
= ‘U’: A is unit triangular.N – [in]
N is INTEGER
The order of the matrix A. N >= 0.
NRHS – [in]
NRHS is INTEGER
The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
A – [in]
A is REAL array, dimension (LDA,N)
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 – [in]
LDA is INTEGER
The leading dimension of the array A. LDA >= fla_max(1,N).
B – [inout]
B is REAL array, dimension (LDB,NRHS)
On entry, the right hand side matrix B. On exit, if INFO = 0, the solution matrix X.
LDB – [in]
LDB is INTEGER
The leading dimension of the array B. LDB >= fla_max(1,N).
INFO – [out]
INFO is INTEGER
= 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.