1SGESV(1)              LAPACK driver routine (version 3.1)             SGESV(1)
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NAME

6       SGESV - the solution to a real system of linear equations  A * X = B,
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SYNOPSIS

9       SUBROUTINE SGESV( N, NRHS, A, LDA, IPIV, B, LDB, INFO )
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11           INTEGER       INFO, LDA, LDB, N, NRHS
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13           INTEGER       IPIV( * )
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15           REAL          A( LDA, * ), B( LDB, * )
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PURPOSE

18       SGESV computes the solution to a real system of linear equations
19          A  *  X  =  B, where A is an N-by-N matrix and X and B are N-by-NRHS
20       matrices.
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22       The LU decomposition with partial pivoting and row interchanges is used
23       to factor A as
24          A = P * L * U,
25       where  P  is a permutation matrix, L is unit lower triangular, and U is
26       upper triangular.  The factored form of A is then  used  to  solve  the
27       system of equations A * X = B.
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ARGUMENTS

31       N       (input) INTEGER
32               The  number  of linear equations, i.e., the order of the matrix
33               A.  N >= 0.
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35       NRHS    (input) INTEGER
36               The number of right hand sides, i.e., the number of columns  of
37               the matrix B.  NRHS >= 0.
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39       A       (input/output) REAL array, dimension (LDA,N)
40               On  entry,  the N-by-N coefficient matrix A.  On exit, the fac‐
41               tors L and U from the factorization A = P*L*U; the unit  diago‐
42               nal elements of L are not stored.
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44       LDA     (input) INTEGER
45               The leading dimension of the array A.  LDA >= max(1,N).
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47       IPIV    (output) INTEGER array, dimension (N)
48               The  pivot  indices that define the permutation matrix P; row i
49               of the matrix was interchanged with row IPIV(i).
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51       B       (input/output) REAL array, dimension (LDB,NRHS)
52               On entry, the N-by-NRHS matrix of right hand side matrix B.  On
53               exit, if INFO = 0, the N-by-NRHS solution matrix X.
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55       LDB     (input) INTEGER
56               The leading dimension of the array B.  LDB >= max(1,N).
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58       INFO    (output) INTEGER
59               = 0:  successful exit
60               < 0:  if INFO = -i, the i-th argument had an illegal value
61               >  0:   if INFO = i, U(i,i) is exactly zero.  The factorization
62               has been completed, but the factor U is  exactly  singular,  so
63               the solution could not be computed.
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67 LAPACK driver routine (version 3.N1o)vember 2006                        SGESV(1)