CTPTRS (3lapack)

solve 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.