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guez |
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! $Header: /home/cvsroot/LMDZ4/libf/filtrez/jacobi.F,v 1.1.1.1 2004/05/19 12:53:09 lmdzadmin Exp $ |
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SUBROUTINE JACOBI(A,N,NP,D,V,NROT) |
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PARAMETER (NMAX=400) |
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DIMENSION A(NP,NP),D(NP),V(NP,NP),B(NMAX),Z(NMAX) |
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IF (n.gt.nmax) THEN |
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print*, 'n, nmax=', n, nmax |
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print*, 'Surdimensionnement insuffisant dans jacobi' |
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stop 1 |
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ENDIF |
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DO 12 IP=1,N |
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DO 11 IQ=1,N |
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V(IP,IQ)=0. |
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11 CONTINUE |
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V(IP,IP)=1. |
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12 CONTINUE |
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DO 13 IP=1,N |
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B(IP)=A(IP,IP) |
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D(IP)=B(IP) |
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Z(IP)=0. |
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13 CONTINUE |
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NROT=0 |
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DO 24 I=1,50 |
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SM=0. |
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DO 15 IP=1,N-1 |
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DO 14 IQ=IP+1,N |
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SM=SM+ABS(A(IP,IQ)) |
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14 CONTINUE |
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15 CONTINUE |
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IF(SM.EQ.0.)RETURN |
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IF(I.LT.4)THEN |
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TRESH=0.2*SM/N**2 |
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ELSE |
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TRESH=0. |
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ENDIF |
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DO 22 IP=1,N-1 |
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DO 21 IQ=IP+1,N |
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G=100.*ABS(A(IP,IQ)) |
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IF((I.GT.4).AND.(ABS(D(IP))+G.EQ.ABS(D(IP))) |
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* .AND.(ABS(D(IQ))+G.EQ.ABS(D(IQ))))THEN |
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A(IP,IQ)=0. |
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ELSE IF(ABS(A(IP,IQ)).GT.TRESH)THEN |
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H=D(IQ)-D(IP) |
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IF(ABS(H)+G.EQ.ABS(H))THEN |
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T=A(IP,IQ)/H |
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ELSE |
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THETA=0.5*H/A(IP,IQ) |
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T=1./(ABS(THETA)+SQRT(1.+THETA**2)) |
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IF(THETA.LT.0.)T=-T |
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ENDIF |
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C=1./SQRT(1+T**2) |
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S=T*C |
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TAU=S/(1.+C) |
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H=T*A(IP,IQ) |
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Z(IP)=Z(IP)-H |
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Z(IQ)=Z(IQ)+H |
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D(IP)=D(IP)-H |
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D(IQ)=D(IQ)+H |
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A(IP,IQ)=0. |
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DO 16 J=1,IP-1 |
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G=A(J,IP) |
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H=A(J,IQ) |
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A(J,IP)=G-S*(H+G*TAU) |
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A(J,IQ)=H+S*(G-H*TAU) |
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16 CONTINUE |
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DO 17 J=IP+1,IQ-1 |
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G=A(IP,J) |
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H=A(J,IQ) |
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A(IP,J)=G-S*(H+G*TAU) |
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A(J,IQ)=H+S*(G-H*TAU) |
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17 CONTINUE |
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DO 18 J=IQ+1,N |
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G=A(IP,J) |
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H=A(IQ,J) |
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A(IP,J)=G-S*(H+G*TAU) |
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A(IQ,J)=H+S*(G-H*TAU) |
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18 CONTINUE |
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DO 19 J=1,N |
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G=V(J,IP) |
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H=V(J,IQ) |
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V(J,IP)=G-S*(H+G*TAU) |
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V(J,IQ)=H+S*(G-H*TAU) |
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19 CONTINUE |
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NROT=NROT+1 |
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ENDIF |
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21 CONTINUE |
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22 CONTINUE |
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DO 23 IP=1,N |
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B(IP)=B(IP)+Z(IP) |
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D(IP)=B(IP) |
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Z(IP)=0. |
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23 CONTINUE |
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24 CONTINUE |
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STOP '50 iterations should never happen' |
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RETURN |
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END |
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