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NAME
     dtptrs - solve a triangular system of the form   A * X  =  B
     or A**T * X = B,

SYNOPSIS
     SUBROUTINE DTPTRS( UPLO, TRANS, DIAG, N, NRHS, AP,  B,  LDB,
               INFO )

     CHARACTER DIAG, TRANS, UPLO

     INTEGER INFO, LDB, N, NRHS

     DOUBLE PRECISION AP( * ), B( LDB, * )



     #include <sunperf.h>

     void dtptrs(char uplo, char trans, char  diag,  int  n,  int
               nrhs, double *dap, double *db, int ldb, int *info)
               ;

PURPOSE
     DTPTRS 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 = Tran-
               spose)

     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)   DOUBLE   PRECISION   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) DOUBLE PRECISION  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 ille-
               gal 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.

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