CGESV - compute the solution to a complex system of linear
equations A * X = B,
SYNOPSIS
SUBROUTINE CGESV( N, NRHS, A, LDA, IPIV, B, LDB, INFO )
INTEGER INFO, LDA, LDB, N, NRHS
INTEGER IPIV( * )
COMPLEX A( LDA, * ), B( LDB, * )
PURPOSE
CGESV computes the solution to a complex 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 triangu
lar, 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) COMPLEX array, dimension (LDA,N)
On entry, the N-by-N coefficient matrix A. On
exit, the factors L and U from the factorization A
= P*L*U; the unit diagonal 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) COMPLEX 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.
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 ille
gal 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.
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