1DTRTRS(1)                LAPACK routine (version 3.2)                DTRTRS(1)
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NAME

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

10       SUBROUTINE DTRTRS( UPLO, TRANS, DIAG, N, NRHS, A, LDA, B, LDB, INFO )
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12           CHARACTER      DIAG, TRANS, UPLO
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14           INTEGER        INFO, LDA, LDB, N, NRHS
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16           DOUBLE         PRECISION A( LDA, * ), B( LDB, * )
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PURPOSE

19       DTRTRS solves a triangular system of the form where A is  a  triangular
20       matrix  of  order  N, and B is an N-by-NRHS matrix.  A check is made to
21       verify that A is nonsingular.
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ARGUMENTS

24       UPLO    (input) CHARACTER*1
25               = 'U':  A is upper triangular;
26               = 'L':  A is lower triangular.
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28       TRANS   (input) CHARACTER*1
29               Specifies the form of the system of equations:
30               = 'N':  A * X = B  (No transpose)
31               = 'T':  A**T * X = B  (Transpose)
32               = 'C':  A**H * X = B  (Conjugate transpose = Transpose)
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34       DIAG    (input) CHARACTER*1
35               = 'N':  A is non-unit triangular;
36               = 'U':  A is unit triangular.
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38       N       (input) INTEGER
39               The order of the matrix A.  N >= 0.
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41       NRHS    (input) INTEGER
42               The number of right hand sides, i.e., the number of columns  of
43               the matrix B.  NRHS >= 0.
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45       A       (input) DOUBLE PRECISION array, dimension (LDA,N)
46               The  triangular  matrix  A.   If UPLO = 'U', the leading N-by-N
47               upper triangular part of the array A contains the upper  trian‐
48               gular  matrix,  and  the strictly lower triangular part of A is
49               not referenced.  If UPLO = 'L', the leading N-by-N lower trian‐
50               gular part of the array A contains the lower triangular matrix,
51               and the strictly upper triangular part of A is not  referenced.
52               If  DIAG  = 'U', the diagonal elements of A are also not refer‐
53               enced and are assumed to be 1.
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55       LDA     (input) INTEGER
56               The leading dimension of the array A.  LDA >= max(1,N).
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58       B       (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
59               On entry, the right hand side matrix B.  On exit, if INFO =  0,
60               the solution matrix X.
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62       LDB     (input) INTEGER
63               The leading dimension of the array B.  LDB >= max(1,N).
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65       INFO    (output) INTEGER
66               = 0:  successful exit
67               < 0: if INFO = -i, the i-th argument had an illegal value
68               > 0: if INFO = i, the i-th diagonal element of A is zero, indi‐
69               cating that the matrix is singular and the solutions X have not
70               been computed.
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74 LAPACK routine (version 3.2)    November 2008                       DTRTRS(1)
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