1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
|
*DECK ALSB
SUBROUTINE ALSB (N,IS,B,IER,MAX)
*
*-----------------------------------------------------------------------
*
*Purpose:
* solution of a system of linear equations using gaussian elimination
* with partial pivoting. Simple 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.
* IS number of right hand vectors.
* B coefficient matrix augmented with the right hand vectors.
* DIMENSION B(MAX,N+IS)
* MAX first dimention of matrix B.
*
*Parameters: output
* B solution vectors, starting at B(1,N+1).
* IER error flag. Execution failure if IER.ne.0.
*
*-----------------------------------------------------------------------
*
DIMENSION B(MAX,*)
IN=0
M=N+IS
IER=0
IF (N.EQ.1) GO TO 100
*
* SEARCH FOR MAXIMUM PIVOT ON COLUMN JCOL.
NM1=N-1
NP1=N+1
DO 60 JCOL=1,NM1
TEST=0.0
DO 10 I=JCOL,N
IF (ABS(B(I,JCOL)).LE.TEST) GO TO 10
TEST=ABS(B(I,JCOL))
IN=I
10 CONTINUE
IF (TEST.EQ.0.0) GO TO 120
*
* TRIANGULARIZATION.
PMX=B(IN,JCOL)
B(IN,JCOL)=B(JCOL,JCOL)
IP1=JCOL+1
DO 50 J=IP1,M
PER=B(IN,J)/PMX
B(IN,J)=B(JCOL,J)
B(JCOL,J)=PER
DO 40 I=IP1,N
B(I,J)=B(I,J)-B(I,JCOL)*PER
40 CONTINUE
50 CONTINUE
60 CONTINUE
PER=B(N,N)
IF (PER.EQ.0.0) GO TO 120
DO 70 J=NP1,M
B(N,J)=B(N,J)/PER
70 CONTINUE
*
* BACK SUBSTITUTION.
DO 95 IN=2,N
I=N-IN+1
IP1=I+1
DO 90 J=NP1,M
PER=B(I,J)
DO 80 K=IP1,N
PER=PER-B(I,K)*B(K,J)
80 CONTINUE
B(I,J)=PER
90 CONTINUE
95 CONTINUE
RETURN
*
100 PER=B(1,1)
IF (PER.EQ.0.0) GO TO 120
DO 110 J=2,M
B(1,J)=B(1,J)/PER
110 CONTINUE
RETURN
120 IER=1
RETURN
END
|
