---
name: "ctptrs"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/ctptrs/3lapack"
---

# ctptrs(3lapack)

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

## NAME

CTPTRS - solves a triangular system of the form   A \* X = B, A\*\*T \* X = B, or A\*\*H \* X = B,

## SYNOPSIS

- SUBROUTINE CTPTRS(

  UPLO, TRANS, DIAG, N, NRHS, AP, B, LDB, INFO )

- CHARACTER

  DIAG, TRANS, UPLO

- INTEGER

  INFO, LDB, N, NRHS

- COMPLEX

  AP( \* ), B( LDB, \* )

## PURPOSE

CTPTRS solves a triangular system of the form where A is a triangular matrix of order N stored in packed format, and B is an N-by-NRHS matrix.  A check is made to verify that A is nonsingular.\

## ARGUMENTS

- UPLO (input) CHARACTER\*1

  \= 'U':  A is upper triangular;\
   \= 'L':  A is lower triangular.

- TRANS (input) 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 (input) CHARACTER\*1

  \= 'N':  A is non-unit triangular;\
   \= 'U':  A is unit triangular.

- N (input) INTEGER

  The order of the matrix A.  N \>= 0.

- NRHS (input) INTEGER

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

- AP (input) COMPLEX array, dimension (N\*(N+1)/2)

  The upper or lower triangular matrix A, packed columnwise in a linear array.  The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)\*j/2) = A(i,j) for 1\<=i\<=j; if UPLO = 'L', AP(i + (j-1)\*(2\*n-j)/2) = A(i,j) for j\<=i\<=n.

- B (input/output) COMPLEX array, dimension (LDB,NRHS)

  On entry, the right hand side matrix B. On exit, if INFO = 0, the solution matrix X.

- LDB (input) INTEGER

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

- INFO (output) 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.