dgetrs(3)

NAME

DGETRS - solve a system of linear equations A * X = B or

A' * X = B with a general N-by-N matrix A using the LU factoriza

tion computed by DGETRF

SYNOPSIS

SUBROUTINE DGETRS( TRANS, N, NRHS, A, LDA, IPIV,  B,  LDB,
INFO )
    CHARACTER      TRANS
    INTEGER        INFO, LDA, LDB, N, NRHS
    INTEGER        IPIV( * )
    DOUBLE         PRECISION A( LDA, * ), B( LDB, * )

PURPOSE

DGETRS solves a system of linear equations A * X = B or A'

* X = B with a general N-by-N matrix A using the LU factorization

computed by DGETRF.

ARGUMENTS

TRANS (input) CHARACTER*1

Specifies the form of the system of equations:
= 'N': A * X = B (No transpose)
= 'T': A'* X = B (Transpose)
= 'C': A'* X = B (Conjugate transpose = Trans

pose)

N (input) INTEGER

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) DOUBLE PRECISION array, dimension (LDA,N)

The factors L and U from the factorization A =

P*L*U as computed by DGETRF.

LDA (input) INTEGER

The leading dimension of the array A. LDA >=

max(1,N).

IPIV (input) INTEGER array, dimension (N)

The pivot indices from DGETRF; for 1<=i<=N, row i

of the matrix was interchanged with row IPIV(i).

B (input/output) DOUBLE PRECISION array, dimension

(LDB,NRHS)

On entry, the right hand side matrix B. On exit,

the 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 ille

gal value

LAPACK version 3.0 15 June 2000

DGETRS(3)