NAME

SGETRS - solve 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 SGETRF

SYNOPSIS

SUBROUTINE SGETRS(
TRANS, N, NRHS, A, LDA, IPIV, B, LDB, INFO )

CHARACTER TRANS

INTEGER INFO, LDA, LDB, N, NRHS

INTEGER IPIV( ∗ )

REAL A( LDA, ∗ ), B( LDB, ∗ )

PURPOSE

SGETRS 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 SGETRF.
 

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 = Transpose)

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) REAL array, dimension (LDA,N)
The factors L and U from the factorization A = P∗L∗U as computed by SGETRF.

LDA     (input) INTEGER
The leading dimension of the array A.  LDA >= max(1,N).

IPIV    (input) INTEGER array, dimension (N)
The pivot indices from SGETRF; for 1<=i<=N, row i of the matrix was interchanged with row IPIV(i).

B       (input/output) REAL 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 illegal value

  —  LAPACK version 2.0  —  08 October 1994