Last change
on this file since 3702 was
1289,
checked in by Ehouarn Millour, 15 years ago
|
Minor improvement: Bring Jacobi into the XXIst century.
Routine can now handle matix of any size (tested on local Linux machines and IBM Power6 that this doesn't change results compared to old version).
EM
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-
Property svn:eol-style set to
native
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Property svn:keywords set to
Author Date Id Revision
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File size:
2.7 KB
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1 | ! |
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2 | ! $Id: jacobi.F90 1289 2009-12-18 14:51:22Z oboucher $ |
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3 | ! |
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4 | SUBROUTINE JACOBI(A,N,NP,D,V,NROT) |
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5 | implicit none |
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6 | ! Arguments: |
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7 | integer,intent(in) :: N |
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8 | integer,intent(in) :: NP |
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9 | integer,intent(out) :: NROT |
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10 | real,intent(inout) :: A(NP,NP) |
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11 | real,intent(out) :: D(NP) |
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12 | real,intent(out) :: V(NP,NP) |
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13 | |
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14 | ! local variables: |
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15 | integer :: IP,IQ,I,J |
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16 | real :: SM,TRESH,G,H,T,THETA,C,S,TAU |
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17 | real :: B(N) |
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18 | real :: Z(N) |
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19 | |
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20 | DO IP=1,N |
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21 | DO IQ=1,N |
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22 | V(IP,IQ)=0. |
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23 | ENDDO |
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24 | V(IP,IP)=1. |
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25 | ENDDO |
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26 | DO IP=1,N |
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27 | B(IP)=A(IP,IP) |
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28 | D(IP)=B(IP) |
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29 | Z(IP)=0. |
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30 | ENDDO |
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31 | NROT=0 |
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32 | DO I=1,50 ! 50? I suspect this should be NP |
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33 | ! but convergence is fast enough anyway |
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34 | SM=0. |
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35 | DO IP=1,N-1 |
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36 | DO IQ=IP+1,N |
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37 | SM=SM+ABS(A(IP,IQ)) |
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38 | ENDDO |
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39 | ENDDO |
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40 | IF(SM.EQ.0.)RETURN |
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41 | IF(I.LT.4)THEN |
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42 | TRESH=0.2*SM/N**2 |
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43 | ELSE |
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44 | TRESH=0. |
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45 | ENDIF |
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46 | DO IP=1,N-1 |
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47 | DO IQ=IP+1,N |
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48 | G=100.*ABS(A(IP,IQ)) |
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49 | IF((I.GT.4).AND.(ABS(D(IP))+G.EQ.ABS(D(IP))) & |
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50 | .AND.(ABS(D(IQ))+G.EQ.ABS(D(IQ))))THEN |
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51 | A(IP,IQ)=0. |
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52 | ELSE IF(ABS(A(IP,IQ)).GT.TRESH)THEN |
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53 | H=D(IQ)-D(IP) |
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54 | IF(ABS(H)+G.EQ.ABS(H))THEN |
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55 | T=A(IP,IQ)/H |
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56 | ELSE |
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57 | THETA=0.5*H/A(IP,IQ) |
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58 | T=1./(ABS(THETA)+SQRT(1.+THETA**2)) |
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59 | IF(THETA.LT.0.)T=-T |
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60 | ENDIF |
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61 | C=1./SQRT(1+T**2) |
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62 | S=T*C |
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63 | TAU=S/(1.+C) |
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64 | H=T*A(IP,IQ) |
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65 | Z(IP)=Z(IP)-H |
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66 | Z(IQ)=Z(IQ)+H |
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67 | D(IP)=D(IP)-H |
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68 | D(IQ)=D(IQ)+H |
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69 | A(IP,IQ)=0. |
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70 | DO J=1,IP-1 |
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71 | G=A(J,IP) |
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72 | H=A(J,IQ) |
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73 | A(J,IP)=G-S*(H+G*TAU) |
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74 | A(J,IQ)=H+S*(G-H*TAU) |
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75 | ENDDO |
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76 | DO J=IP+1,IQ-1 |
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77 | G=A(IP,J) |
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78 | H=A(J,IQ) |
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79 | A(IP,J)=G-S*(H+G*TAU) |
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80 | A(J,IQ)=H+S*(G-H*TAU) |
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81 | ENDDO |
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82 | DO J=IQ+1,N |
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83 | G=A(IP,J) |
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84 | H=A(IQ,J) |
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85 | A(IP,J)=G-S*(H+G*TAU) |
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86 | A(IQ,J)=H+S*(G-H*TAU) |
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87 | ENDDO |
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88 | DO J=1,N |
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89 | G=V(J,IP) |
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90 | H=V(J,IQ) |
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91 | V(J,IP)=G-S*(H+G*TAU) |
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92 | V(J,IQ)=H+S*(G-H*TAU) |
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93 | ENDDO |
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94 | NROT=NROT+1 |
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95 | ENDIF |
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96 | ENDDO |
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97 | ENDDO |
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98 | DO IP=1,N |
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99 | B(IP)=B(IP)+Z(IP) |
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100 | D(IP)=B(IP) |
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101 | Z(IP)=0. |
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102 | ENDDO |
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103 | ENDDO ! of DO I=1,50 |
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104 | STOP 'Jacobi: 50 iterations should never happen' |
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105 | RETURN |
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106 | END SUBROUTINE JACOBI |
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