CTPTRS(3)                  MathKeisan LAPACK routine                 CTPTRS(3)



NAME
       CTPTRS  - 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 nonsin-
       gular.


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.



 LAPACK routine (version 3.1)    November 2006                       CTPTRS(3)