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131 lines
3.7 KiB
Fortran
131 lines
3.7 KiB
Fortran
*DECK LA05BD
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SUBROUTINE LA05BD (A, IND, IA, N, IP, IW, W, G, B, TRANS)
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C***BEGIN PROLOGUE LA05BD
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C***SUBSIDIARY
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C***PURPOSE Subsidiary to DSPLP
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C***LIBRARY SLATEC
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C***TYPE DOUBLE PRECISION (LA05BS-S, LA05BD-D)
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C***AUTHOR (UNKNOWN)
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C***DESCRIPTION
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C
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C THIS SUBPROGRAM IS A SLIGHT MODIFICATION OF A SUBPROGRAM
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C FROM THE C. 1979 AERE HARWELL LIBRARY. THE NAME OF THE
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C CORRESPONDING HARWELL CODE CAN BE OBTAINED BY DELETING
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C THE FINAL LETTER =D= IN THE NAMES USED HERE.
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C REVISED SEP. 13, 1979.
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C
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C ROYALTIES HAVE BEEN PAID TO AERE-UK FOR USE OF THEIR CODES
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C IN THE PACKAGE GIVEN HERE. ANY PRIMARY USAGE OF THE HARWELL
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C SUBROUTINES REQUIRES A ROYALTY AGREEMENT AND PAYMENT BETWEEN
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C THE USER AND AERE-UK. ANY USAGE OF THE SANDIA WRITTEN CODES
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C DSPLP( ) (WHICH USES THE HARWELL SUBROUTINES) IS PERMITTED.
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C
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C IP(I,1),IP(I,2) POINT TO START OF ROW/COLUMN I OF U.
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C IW(I,1),IW(I,2) ARE LENGTHS OF ROW/COL I OF U.
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C IW(.,3),IW(.,4) HOLD ROW/COL NUMBERS IN PIVOTAL ORDER.
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C
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C***SEE ALSO DSPLP
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C***ROUTINES CALLED XERMSG, XSETUN
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C***COMMON BLOCKS LA05DD
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C***REVISION HISTORY (YYMMDD)
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C 811215 DATE WRITTEN
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C 890531 Changed all specific intrinsics to generic. (WRB)
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C 890831 Modified array declarations. (WRB)
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C 891214 Prologue converted to Version 4.0 format. (BAB)
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C 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
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C 900402 Added TYPE section. (WRB)
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C 920410 Corrected second dimension on IW declaration. (WRB)
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C***END PROLOGUE LA05BD
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DOUBLE PRECISION A(*), B(*), AM, W(*), G, SMALL
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LOGICAL TRANS
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INTEGER IND(IA,2), IW(N,8)
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INTEGER IP(N,2)
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COMMON /LA05DD/ SMALL, LP, LENL, LENU, NCP, LROW, LCOL
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C***FIRST EXECUTABLE STATEMENT LA05BD
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IF (G.LT.0.D0) GO TO 130
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KLL = IA - LENL + 1
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IF (TRANS) GO TO 80
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C
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C MULTIPLY VECTOR BY INVERSE OF L
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IF (LENL.LE.0) GO TO 20
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L1 = IA + 1
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DO 10 KK=1,LENL
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K = L1 - KK
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I = IND(K,1)
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IF (B(I).EQ.0.D0) GO TO 10
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J = IND(K,2)
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B(J) = B(J) + A(K)*B(I)
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10 CONTINUE
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20 DO 30 I=1,N
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W(I) = B(I)
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B(I) = 0.D0
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30 CONTINUE
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C
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C MULTIPLY VECTOR BY INVERSE OF U
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N1 = N + 1
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DO 70 II=1,N
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I = N1 - II
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I = IW(I,3)
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AM = W(I)
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KP = IP(I,1)
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IF (KP.GT.0) GO TO 50
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KP = -KP
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IP(I,1) = KP
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NZ = IW(I,1)
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KL = KP - 1 + NZ
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K2 = KP + 1
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DO 40 K=K2,KL
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J = IND(K,2)
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AM = AM - A(K)*B(J)
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40 CONTINUE
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50 IF (AM.EQ.0.) GO TO 70
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J = IND(KP,2)
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B(J) = AM/A(KP)
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KPC = IP(J,2)
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KL = IW(J,2) + KPC - 1
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IF (KL.EQ.KPC) GO TO 70
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K2 = KPC + 1
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DO 60 K=K2,KL
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I = IND(K,1)
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IP(I,1) = -ABS(IP(I,1))
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60 CONTINUE
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70 CONTINUE
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GO TO 140
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C
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C MULTIPLY VECTOR BY INVERSE OF TRANSPOSE OF U
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80 DO 90 I=1,N
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W(I) = B(I)
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B(I) = 0.D0
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90 CONTINUE
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DO 110 II=1,N
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I = IW(II,4)
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AM = W(I)
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IF (AM.EQ.0.D0) GO TO 110
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J = IW(II,3)
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KP = IP(J,1)
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AM = AM/A(KP)
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B(J) = AM
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KL = IW(J,1) + KP - 1
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IF (KP.EQ.KL) GO TO 110
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K2 = KP + 1
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DO 100 K=K2,KL
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I = IND(K,2)
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W(I) = W(I) - AM*A(K)
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100 CONTINUE
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110 CONTINUE
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C
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C MULTIPLY VECTOR BY INVERSE OF TRANSPOSE OF L
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IF (KLL.GT.IA) RETURN
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DO 120 K=KLL,IA
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J = IND(K,2)
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IF (B(J).EQ.0.D0) GO TO 120
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I = IND(K,1)
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B(I) = B(I) + A(K)*B(J)
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120 CONTINUE
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GO TO 140
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C
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130 CALL XSETUN(LP)
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IF (LP .GT. 0) CALL XERMSG ('SLATEC', 'LA05BD',
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+ 'EARLIER ENTRY GAVE ERROR RETURN.', -8, 2)
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140 RETURN
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END
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