1STRSV(1)                         BLAS routine                         STRSV(1)
2
3
4

NAME

6       STRSV - one of the systems of equations   A*x = b, or A'*x = b,
7

SYNOPSIS

9       SUBROUTINE STRSV(UPLO,TRANS,DIAG,N,A,LDA,X,INCX)
10
11           INTEGER                                      INCX,LDA,N
12
13           CHARACTER                                    DIAG,TRANS,UPLO
14
15           REAL                                         A(LDA,*),X(*)
16

PURPOSE

18       STRSV  solves one of the systems of equations
19
20       where  b  and  x are n element vectors and A is an n by n unit, or non-
21       unit, upper or lower triangular matrix.
22
23       No test for singularity or near-singularity is included  in  this  rou‐
24       tine. Such tests must be performed before calling this routine.
25
26

ARGUMENTS

28       UPLO   - CHARACTER*1.
29              On entry, UPLO specifies whether the matrix is an upper or lower
30              triangular matrix as follows:
31
32              UPLO = 'U' or 'u'   A is an upper triangular matrix.
33
34              UPLO = 'L' or 'l'   A is a lower triangular matrix.
35
36              Unchanged on exit.
37
38       TRANS  - CHARACTER*1.
39              On entry, TRANS specifies the equations to be solved as follows:
40
41              TRANS = 'N' or 'n'   A*x = b.
42
43              TRANS = 'T' or 't'   A'*x = b.
44
45              TRANS = 'C' or 'c'   A'*x = b.
46
47              Unchanged on exit.
48
49       DIAG   - CHARACTER*1.
50              On entry, DIAG specifies whether or not A is unit triangular  as
51              follows:
52
53              DIAG = 'U' or 'u'   A is assumed to be unit triangular.
54
55              DIAG = 'N' or 'n'   A is not assumed to be unit triangular.
56
57              Unchanged on exit.
58
59       N      - INTEGER.
60              On  entry,  N specifies the order of the matrix A.  N must be at
61              least zero.  Unchanged on exit.
62
63       A      - REAL             array of DIMENSION ( LDA, n ).
64              Before entry with  UPLO = 'U' or 'u', the leading n by  n  upper
65              triangular part of the array A must contain the upper triangular
66              matrix and the strictly lower triangular part of A is not refer‐
67              enced.   Before entry with UPLO = 'L' or 'l', the leading n by n
68              lower triangular part of the array A must contain the lower tri‐
69              angular  matrix  and  the strictly upper triangular part of A is
70              not referenced.  Note that when  DIAG = 'U' or 'u', the diagonal
71              elements  of  A are not referenced either, but are assumed to be
72              unity.  Unchanged on exit.
73
74       LDA    - INTEGER.
75              On entry, LDA specifies the first dimension of A as declared  in
76              the  calling  (sub)  program.  LDA must be at least max( 1, n ).
77              Unchanged on exit.
78
79       X      - REAL             array of dimension at least
80              ( 1 + ( n - 1 )*abs( INCX ) ).  Before  entry,  the  incremented
81              array  X must contain the n element right-hand side vector b. On
82              exit, X is overwritten with the solution vector x.
83
84       INCX   - INTEGER.
85              On entry, INCX specifies the increment for the  elements  of  X.
86              INCX must not be zero.  Unchanged on exit.
87
88              Level 2 Blas routine.
89
90              --  Written on 22-October-1986.  Jack Dongarra, Argonne National
91              Lab.  Jeremy Du Croz, Nag Central Office.  Sven Hammarling,  Nag
92              Central Office.  Richard Hanson, Sandia National Labs.
93
94
95
96BLAS routine                     November 2006                        STRSV(1)