DGESV(1) LAPACK driver routine (version 3.2) DGESV(1)NAME
DGESV - computes the solution to a real system of linear equations A *
X = B,
SYNOPSIS
SUBROUTINE DGESV( N, NRHS, A, LDA, IPIV, B, LDB, INFO )
INTEGER INFO, LDA, LDB, N, NRHS
INTEGER IPIV( * )
DOUBLE PRECISION A( LDA, * ), B( LDB, * )
PURPOSE
DGESV computes the solution to a real system of linear equations
A * X = B, where A is an N-by-N matrix and X and B are N-by-NRHS
matrices. The LU decomposition with partial pivoting and row inter‐
changes is used to factor A as
A = P * L * U,
where P is a permutation matrix, L is unit lower triangular, and U is
upper triangular. The factored form of A is then used to solve the
system of equations A * X = B.
ARGUMENTS
N (input) INTEGER
The number of linear equations, i.e., the order of the matrix
A. N >= 0.
NRHS (input) INTEGER
The number of right hand sides, i.e., the number of columns of
the matrix B. NRHS >= 0.
A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
On entry, the N-by-N coefficient matrix A. On exit, the fac‐
tors L and U from the factorization A = P*L*U; the unit diago‐
nal elements of L are not stored.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
IPIV (output) INTEGER array, dimension (N)
The pivot indices that define the permutation matrix P; row i
of the matrix was interchanged with row IPIV(i).
B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
On entry, the N-by-NRHS matrix of right hand side matrix B. On
exit, if INFO = 0, the N-by-NRHS solution matrix X.
LDB (input) INTEGER
The leading dimension of the array B. LDB >= max(1,N).
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, U(i,i) is exactly zero. The factorization
has been completed, but the factor U is exactly singular, so
the solution could not be computed.
LAPACK driver routine (version 3November 2008 DGESV(1)
