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dtptrs

 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, * )

 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((j-1)*j/2 + i) = A(i,j) for 1<=i<=j; if UPLO =
              'L', AP((j-1)*(n-j) + j*(j+1)/2 + i-j) = A(i,j) for
              j<=i<=n.

 (LDB,NRHS)
      B       (input/output) DOUBLE PRECISION array, dimension
              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.