1STRSV(1)                         BLAS routine                         STRSV(1)
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NAME

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

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

18       STRSV  solves one of the systems of equations
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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.
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23       No test for singularity or near-singularity is included  in  this  rou‐
24       tine. Such tests must be performed before calling this routine.
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ARGUMENTS

28       UPLO   - CHARACTER*1.
29              On entry, UPLO specifies whether the matrix is an upper or lower
30              triangular matrix as follows:
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32              UPLO = 'U' or 'u'   A is an upper triangular matrix.
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34              UPLO = 'L' or 'l'   A is a lower triangular matrix.
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36              Unchanged on exit.
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38       TRANS  - CHARACTER*1.
39              On entry, TRANS specifies the equations to be solved as follows:
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41              TRANS = 'N' or 'n'   A*x = b.
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43              TRANS = 'T' or 't'   A'*x = b.
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45              TRANS = 'C' or 'c'   A'*x = b.
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47              Unchanged on exit.
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49       DIAG   - CHARACTER*1.
50              On entry, DIAG specifies whether or not A is unit triangular  as
51              follows:
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53              DIAG = 'U' or 'u'   A is assumed to be unit triangular.
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55              DIAG = 'N' or 'n'   A is not assumed to be unit triangular.
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57              Unchanged on exit.
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59       N      - INTEGER.
60              On  entry,  N specifies the order of the matrix A.  N must be at
61              least zero.  Unchanged on exit.
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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.
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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.
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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.
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84       INCX   - INTEGER.
85              On entry, INCX specifies the increment for the  elements  of  X.
86              INCX must not be zero.  Unchanged on exit.
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FURTHER DETAILS

89       Level 2 Blas routine.
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91       -- Written on 22-October-1986.
92          Jack Dongarra, Argonne National Lab.
93          Jeremy Du Croz, Nag Central Office.
94          Sven Hammarling, Nag Central Office.
95          Richard Hanson, Sandia National Labs.
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100BLAS routine                     November 2008                        STRSV(1)