mirror of
https://git.planet-casio.com/Lephenixnoir/OpenLibm.git
synced 2025-01-01 06:23:39 +01:00
103 lines
2.8 KiB
Fortran
103 lines
2.8 KiB
Fortran
*DECK PROD
|
|
SUBROUTINE PROD (ND, BD, NM1, BM1, NM2, BM2, NA, AA, X, Y, M, A,
|
|
+ B, C, D, W, U)
|
|
C***BEGIN PROLOGUE PROD
|
|
C***SUBSIDIARY
|
|
C***PURPOSE Subsidiary to BLKTRI
|
|
C***LIBRARY SLATEC
|
|
C***TYPE SINGLE PRECISION (PROD-S, PROC-C)
|
|
C***AUTHOR (UNKNOWN)
|
|
C***DESCRIPTION
|
|
C
|
|
C PROD applies a sequence of matrix operations to the vector X and
|
|
C stores the result in Y.
|
|
C
|
|
C BD,BM1,BM2 are arrays containing roots of certain B polynomials.
|
|
C ND,NM1,NM2 are the lengths of the arrays BD,BM1,BM2 respectively.
|
|
C AA Array containing scalar multipliers of the vector X.
|
|
C NA is the length of the array AA.
|
|
C X,Y The matrix operations are applied to X and the result is Y.
|
|
C A,B,C are arrays which contain the tridiagonal matrix.
|
|
C M is the order of the matrix.
|
|
C D,W,U are working arrays.
|
|
C IS determines whether or not a change in sign is made.
|
|
C
|
|
C***SEE ALSO BLKTRI
|
|
C***ROUTINES CALLED (NONE)
|
|
C***REVISION HISTORY (YYMMDD)
|
|
C 801001 DATE WRITTEN
|
|
C 891214 Prologue converted to Version 4.0 format. (BAB)
|
|
C 900402 Added TYPE section. (WRB)
|
|
C***END PROLOGUE PROD
|
|
C
|
|
DIMENSION A(*) ,B(*) ,C(*) ,X(*) ,
|
|
1 Y(*) ,D(*) ,W(*) ,BD(*) ,
|
|
2 BM1(*) ,BM2(*) ,AA(*) ,U(*)
|
|
C***FIRST EXECUTABLE STATEMENT PROD
|
|
DO 101 J=1,M
|
|
W(J) = X(J)
|
|
Y(J) = W(J)
|
|
101 CONTINUE
|
|
MM = M-1
|
|
ID = ND
|
|
IBR = 0
|
|
M1 = NM1
|
|
M2 = NM2
|
|
IA = NA
|
|
102 IF (IA) 105,105,103
|
|
103 RT = AA(IA)
|
|
IF (ND .EQ. 0) RT = -RT
|
|
IA = IA-1
|
|
C
|
|
C SCALAR MULTIPLICATION
|
|
C
|
|
DO 104 J=1,M
|
|
Y(J) = RT*W(J)
|
|
104 CONTINUE
|
|
105 IF (ID) 125,125,106
|
|
106 RT = BD(ID)
|
|
ID = ID-1
|
|
IF (ID .EQ. 0) IBR = 1
|
|
C
|
|
C BEGIN SOLUTION TO SYSTEM
|
|
C
|
|
D(M) = A(M)/(B(M)-RT)
|
|
W(M) = Y(M)/(B(M)-RT)
|
|
DO 107 J=2,MM
|
|
K = M-J
|
|
DEN = B(K+1)-RT-C(K+1)*D(K+2)
|
|
D(K+1) = A(K+1)/DEN
|
|
W(K+1) = (Y(K+1)-C(K+1)*W(K+2))/DEN
|
|
107 CONTINUE
|
|
DEN = B(1)-RT-C(1)*D(2)
|
|
W(1) = 1.
|
|
IF (DEN) 108,109,108
|
|
108 W(1) = (Y(1)-C(1)*W(2))/DEN
|
|
109 DO 110 J=2,M
|
|
W(J) = W(J)-D(J)*W(J-1)
|
|
110 CONTINUE
|
|
IF (NA) 113,113,102
|
|
111 DO 112 J=1,M
|
|
Y(J) = W(J)
|
|
112 CONTINUE
|
|
IBR = 1
|
|
GO TO 102
|
|
113 IF (M1) 114,114,115
|
|
114 IF (M2) 111,111,120
|
|
115 IF (M2) 117,117,116
|
|
116 IF (ABS(BM1(M1))-ABS(BM2(M2))) 120,120,117
|
|
117 IF (IBR) 118,118,119
|
|
118 IF (ABS(BM1(M1)-BD(ID))-ABS(BM1(M1)-RT)) 111,119,119
|
|
119 RT = RT-BM1(M1)
|
|
M1 = M1-1
|
|
GO TO 123
|
|
120 IF (IBR) 121,121,122
|
|
121 IF (ABS(BM2(M2)-BD(ID))-ABS(BM2(M2)-RT)) 111,122,122
|
|
122 RT = RT-BM2(M2)
|
|
M2 = M2-1
|
|
123 DO 124 J=1,M
|
|
Y(J) = Y(J)+RT*W(J)
|
|
124 CONTINUE
|
|
GO TO 102
|
|
125 RETURN
|
|
END
|