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*DECK ALINVD
SUBROUTINE ALINVD(N,A,MAX,IER)
*
*-----------------------------------------------------------------------
*
*Purpose:
* in-place inversion of a non singular matrix using gaussian elimination
* with partial pivoting. Double precision version.
*
*Copyright:
* Copyright (C) 1993 Ecole Polytechnique de Montreal
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version
*
*Author(s): A. Hebert
*
*Parameters: input
* N order of the coefficient matrix.
* A coefficient matrix to be inverted.
* MAX first dimention of matrix A.
*
*Parameters: output
* A inverted matrix.
* IER error flag (execution failure if IER.ne.0).
*
*-----------------------------------------------------------------------
*
IMPLICIT DOUBLE PRECISION (A-H,O-Z)
*----
* SUBROUTINE ARGUMENTS
*----
INTEGER N,MAX,IER
DOUBLE PRECISION A(MAX,N)
*----
* ALLOCATABLE ARRAY
*----
INTEGER, DIMENSION(:), ALLOCATABLE :: IND
*
ALLOCATE(IND(N))
IN=0
IER=0
DO 1 I=1,N
IND(I)=I
1 CONTINUE
DO 12 J=1,N
TEST=0.0D0
DO 2 I=J,N
IF (ABS(A(I,J)).LE.TEST) GO TO 2
TEST=ABS(A(I,J))
IN=I
2 CONTINUE
IF (TEST.NE.0.0D0) GO TO 3
IER=1
DEALLOCATE(IND)
RETURN
3 PMX=A(IN,J)
A(IN,J)=1.0D0
DO 4 I=1,N
PER=A(IN,I)/PMX
A(IN,I)=A(J,I)
A(J,I)=PER
4 CONTINUE
IPER=IND(IN)
IND(IN)=IND(J)
IND(J)=IPER
DO 11 I=1,N
IF (I.EQ.J) GO TO 11
PMX=A(I,J)
A(I,J)=0.0D0
DO 9 K=1,N
A(I,K)=A(I,K)-PMX*A(J,K)
9 CONTINUE
11 CONTINUE
12 CONTINUE
DO 16 J=1,N
DO 13 K=J,N
IF (IND(K).NE.J) GO TO 13
IN=K
GO TO 14
13 CONTINUE
14 DO 15 I=1,N
PER=A(I,J)
A(I,J)=A(I,IN)
A(I,IN)=PER
IND(IN)=IND(J)
15 CONTINUE
16 CONTINUE
DEALLOCATE(IND)
RETURN
END
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