mirror of
https://github.com/saitohirga/WSJT-X.git
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60 lines
1.5 KiB
Fortran
60 lines
1.5 KiB
Fortran
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subroutine afc65b(cx,npts,fsample,nflip,a,ccfbest,dtbest)
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! Find delta f, f1, f2 ==> a(1:3)
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complex cx(npts)
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real a(5),deltaa(5)
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a(1)=0.
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a(2)=0.
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a(3)=0.
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a(4)=0.
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deltaa(1)=2.0
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deltaa(2)=2.0
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deltaa(3)=2.0
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deltaa(4)=0.05
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nterms=3 !Maybe 2 is enough?
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! Start the iteration
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chisqr=0.
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chisqr0=1.e6
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do iter=1,3 !One iteration is enough?
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do j=1,nterms
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chisq1=fchisq65(cx,npts,fsample,nflip,a,ccfmax,dtmax)
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fn=0.
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delta=deltaa(j)
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10 a(j)=a(j)+delta
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chisq2=fchisq65(cx,npts,fsample,nflip,a,ccfmax,dtmax)
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if(chisq2.eq.chisq1) go to 10
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if(chisq2.gt.chisq1) then
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delta=-delta !Reverse direction
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a(j)=a(j)+delta
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tmp=chisq1
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chisq1=chisq2
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chisq2=tmp
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endif
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20 fn=fn+1.0
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a(j)=a(j)+delta
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chisq3=fchisq65(cx,npts,fsample,nflip,a,ccfmax,dtmax)
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if(chisq3.lt.chisq2) then
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chisq1=chisq2
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chisq2=chisq3
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go to 20
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endif
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! Find minimum of parabola defined by last three points
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delta=delta*(1./(1.+(chisq1-chisq2)/(chisq3-chisq2))+0.5)
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a(j)=a(j)-delta
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deltaa(j)=deltaa(j)*fn/3.
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enddo
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chisqr=fchisq65(cx,npts,fsample,nflip,a,ccfmax,dtmax)
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if(chisqr/chisqr0.gt.0.9999) go to 30
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chisqr0=chisqr
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enddo
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30 ccfbest=ccfmax * (1378.125/fsample)**2
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dtbest=dtmax
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return
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end subroutine afc65b
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