# ctrtrs.f man page

ctrtrs.f —

## Synopsis

### Functions/Subroutines

subroutinectrtrs(UPLO, TRANS, DIAG, N, NRHS, A, LDA, B, LDB, INFO)CTRTRS

## Function/Subroutine Documentation

### subroutine ctrtrs (characterUPLO, characterTRANS, characterDIAG, integerN, integerNRHS, complex, dimension( lda, * )A, integerLDA, complex, dimension( ldb, * )B, integerLDB, integerINFO)

**CTRTRS**

**Purpose:**

```
CTRTRS solves a triangular system of the form
A * X = B, A**T * X = B, or A**H * 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*

```
UPLO is CHARACTER*1
= 'U': A is upper triangular;
= 'L': A is lower triangular.
```

*TRANS*

```
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)
```

*DIAG*

```
DIAG is CHARACTER*1
= 'N': A is non-unit triangular;
= 'U': A is unit triangular.
```

*N*

```
N is INTEGER
The order of the matrix A. N >= 0.
```

*NRHS*

```
NRHS is INTEGER
The number of right hand sides, i.e., the number of columns
of the matrix B. NRHS >= 0.
```

*A*

```
A is COMPLEX 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*

```
LDA is INTEGER
The leading dimension of the array A. LDA >= max(1,N).
```

*B*

```
B is COMPLEX array, dimension (LDB,NRHS)
On entry, the right hand side matrix B.
On exit, if INFO = 0, the solution matrix X.
```

*LDB*

```
LDB is INTEGER
The leading dimension of the array B. LDB >= max(1,N).
```

*INFO*

```
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.
```

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

November 2011

Definition at line 140 of file ctrtrs.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

ctrtrs(3) is an alias of ctrtrs.f(3).