1DTPTRS(1)                LAPACK routine (version 3.1)                DTPTRS(1)
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NAME

6       DTPTRS - a triangular system of the form   A * X = B or A**T * X = B,
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SYNOPSIS

9       SUBROUTINE DTPTRS( UPLO, TRANS, DIAG, N, NRHS, AP, B, LDB, INFO )
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11           CHARACTER      DIAG, TRANS, UPLO
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13           INTEGER        INFO, LDB, N, NRHS
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15           DOUBLE         PRECISION AP( * ), B( LDB, * )
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PURPOSE

18       DTPTRS solves a triangular system of the form
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20       where  A is a triangular matrix of order N stored in packed format, and
21       B is an N-by-NRHS matrix.  A check is made to verify that A is  nonsin‐
22       gular.
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ARGUMENTS

26       UPLO    (input) CHARACTER*1
27               = 'U':  A is upper triangular;
28               = 'L':  A is lower triangular.
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30       TRANS   (input) CHARACTER*1
31               Specifies the form of the system of equations:
32               = 'N':  A * X = B  (No transpose)
33               = 'T':  A**T * X = B  (Transpose)
34               = 'C':  A**H * X = B  (Conjugate transpose = Transpose)
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36       DIAG    (input) CHARACTER*1
37               = 'N':  A is non-unit triangular;
38               = 'U':  A is unit triangular.
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40       N       (input) INTEGER
41               The order of the matrix A.  N >= 0.
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43       NRHS    (input) INTEGER
44               The  number of right hand sides, i.e., the number of columns of
45               the matrix B.  NRHS >= 0.
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47       AP      (input) DOUBLE PRECISION array, dimension (N*(N+1)/2)
48               The upper or lower triangular matrix A, packed columnwise in  a
49               linear  array.   The j-th column of A is stored in the array AP
50               as follows: if UPLO = 'U',  AP(i  +  (j-1)*j/2)  =  A(i,j)  for
51               1<=i<=j;  if  UPLO  = 'L', AP(i + (j-1)*(2*n-j)/2) = A(i,j) for
52               j<=i<=n.
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54       B       (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
55               On entry, the right hand side matrix B.  On exit, if INFO =  0,
56               the solution matrix X.
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58       LDB     (input) INTEGER
59               The leading dimension of the array B.  LDB >= max(1,N).
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61       INFO    (output) INTEGER
62               = 0:  successful exit
63               < 0:  if INFO = -i, the i-th argument had an illegal value
64               >  0:   if  INFO  =  i, the i-th diagonal element of A is zero,
65               indicating that the matrix is singular and the solutions X have
66               not been computed.
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70 LAPACK routine (version 3.1)    November 2006                       DTPTRS(1)
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