1CTRTRS(1)                LAPACK routine (version 3.1)                CTRTRS(1)
2
3
4

NAME

6       CTRTRS  - a triangular system of the form   A * X = B, A**T * X = B, or
7       A**H * X = B,
8

SYNOPSIS

10       SUBROUTINE CTRTRS( UPLO, TRANS, DIAG, N, NRHS, A, LDA, B, LDB, INFO )
11
12           CHARACTER      DIAG, TRANS, UPLO
13
14           INTEGER        INFO, LDA, LDB, N, NRHS
15
16           COMPLEX        A( LDA, * ), B( LDB, * )
17

PURPOSE

19       CTRTRS solves a triangular system of the form
20
21       where A is a triangular matrix of  order  N,  and  B  is  an  N-by-NRHS
22       matrix.  A check is made to verify that A is nonsingular.
23
24

ARGUMENTS

26       UPLO    (input) CHARACTER*1
27               = 'U':  A is upper triangular;
28               = 'L':  A is lower triangular.
29
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)
35
36       DIAG    (input) CHARACTER*1
37               = 'N':  A is non-unit triangular;
38               = 'U':  A is unit triangular.
39
40       N       (input) INTEGER
41               The order of the matrix A.  N >= 0.
42
43       NRHS    (input) INTEGER
44               The  number of right hand sides, i.e., the number of columns of
45               the matrix B.  NRHS >= 0.
46
47       A       (input) COMPLEX array, dimension (LDA,N)
48               The triangular matrix A.  If UPLO =  'U',  the  leading  N-by-N
49               upper  triangular part of the array A contains the upper trian‐
50               gular matrix, and the strictly lower triangular part  of  A  is
51               not referenced.  If UPLO = 'L', the leading N-by-N lower trian‐
52               gular part of the array A contains the lower triangular matrix,
53               and  the strictly upper triangular part of A is not referenced.
54               If DIAG = 'U', the diagonal elements of A are also  not  refer‐
55               enced and are assumed to be 1.
56
57       LDA     (input) INTEGER
58               The leading dimension of the array A.  LDA >= max(1,N).
59
60       B       (input/output) COMPLEX array, dimension (LDB,NRHS)
61               On  entry, the right hand side matrix B.  On exit, if INFO = 0,
62               the solution matrix X.
63
64       LDB     (input) INTEGER
65               The leading dimension of the array B.  LDB >= max(1,N).
66
67       INFO    (output) INTEGER
68               = 0:  successful exit
69               < 0: if INFO = -i, the i-th argument had an illegal value
70               > 0: if INFO = i, the i-th diagonal element of A is zero, indi‐
71               cating that the matrix is singular and the solutions X have not
72               been computed.
73
74
75
76 LAPACK routine (version 3.1)    November 2006                       CTRTRS(1)