
CGESV(l) ) CGESV(l)
NAME
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 NbyN matrix and X and B are NbyNRHS matrices.
The LU decomposition with partial pivoting and row interchanges 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) COMPLEX array, dimension (LDA,N)
On entry, the NbyN 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 NbyNRHS matrix of right hand side matrix B. On exit, if INFO = 0,
the NbyNRHS 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 ith 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 version 3.0 15 June 2000 CGESV(l) 
