mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-25 13:48:42 -05:00
Streamline decoding to use a single call to decode174_91.
This commit is contained in:
Steven Franke
parent
27b94e2cc7
commit
9b6dd092c5
@ -105,19 +105,9 @@ program ldpcsim174_91
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llr(1:nap)=5*(2.0*msgbits(1:nap)-1.0)
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apmask=0
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apmask(1:nap)=1
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! max_iterations is max number of belief propagation iterations
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call bpdecode174_91(llr, apmask, max_iterations, message77, cw, nhardbp,niterations,ncheck)
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if( ndepth .ge. 0 .and. nhardbp .lt. 0 ) then
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dmin=0.0
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if(nbposd.eq.0) then
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call osd174_91(llr,Keff,apmask,ndepth,message91,cw,nhardosd,dmin)
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elseif(nbposd.gt.0) then
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maxsuper=nbposd
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call decode174_91(llr,Keff,ndepth,apmask,maxsuper,message91,cw,nhardosd,niterations,ncheck,dmin)
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endif
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call decode174_91(llr,Keff,nbposd,ndepth,apmask,message91,cw,ntype,nharderrors,dmin)
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! If the decoder finds a valid codeword, nharderrors will be .ge. 0.
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endif
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if( nhardbp .ge. 0 .or. nhardosd.ge.0 ) then
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if( nharderrors.ge.0 ) then
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nhw=count(cw.ne.codeword)
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if(nhw.eq.0) then ! this is a good decode
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ngood=ngood+1
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@ -407,27 +407,19 @@ contains
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endif
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message77=0
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dmin=0.0
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call timer('bpdec174',0)
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call bpdecode174_91(llr,apmask,max_iterations,message77, &
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cw,nharderror,niterations,ncheck)
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call timer('bpdec174',1)
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if(doosd .and. nharderror.lt.0) then
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! ndeep=3
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ndeep=2
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if(abs(nfqso-f1).le.napwid) then
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! ndeep=4
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ndeep=3
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endif
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call timer('osd174_91 ',0)
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Keff=91
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maxsuper=1
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! call osd174_91(llr,Keff,apmask,ndeep,message91,cw,nharderror,dmin)
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call decode174_91(llr,Keff,ndeep,apmask,maxsuper,message91,cw,nharderror, &
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niterations,ncheck,dmin)
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message77=message91(1:77)
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call timer('osd174_91 ',1)
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ndeep=2
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maxosd=1
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if(abs(nfqso-f1).le.napwid) then
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maxosd=2
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endif
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if(.not.doosd) maxosd = -1
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call timer('dec174_91 ',0)
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Keff=91
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call decode174_91(llr,Keff,maxosd,ndeep,apmask,message91,cw, &
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ntype,nharderror,dmin)
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message77=message91(1:77)
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call timer('dec174_91 ',1)
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if(sum(message77).eq.0) cycle
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if( nharderror.ge.0 ) then
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@ -1,133 +1,155 @@
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subroutine decode174_91(llr,Keff,ndeep,apmask,maxsuper,message91,cw,nharderror,iter,ncheck,dmin)
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subroutine decode174_91(llr,Keff,maxosd,norder,apmask,message91,cw,ntype,nharderror,dmin)
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!
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! A hybrid bp/osd decoder for the (174,91) code.
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!
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integer, parameter:: N=174, K=91, M=N-K
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integer*1 cw(N),apmask(N)
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integer*1 nxor(N),hdec(N)
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integer*1 message91(91),m96(96)
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integer nrw(M),ncw
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integer Nm(7,M)
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integer Mn(3,N) ! 3 checks per bit
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integer synd(M)
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real tov(3,N)
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real toc(7,M)
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real tanhtoc(7,M)
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real zn(N),zsum(N)
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real llr(N)
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real Tmn
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! maxosd<0: do bp only
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! maxosd=0: do bp and then call osd once with channel llrs
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! maxosd>1: do bp and then call osd maxosd times with saved bp outputs
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! norder : osd decoding depth
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!
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integer, parameter:: N=174, K=91, M=N-K
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integer*1 cw(N),apmask(N)
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integer*1 nxor(N),hdec(N)
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integer*1 message91(91),m96(96)
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integer nrw(M),ncw
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integer Nm(7,M)
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integer Mn(3,N) ! 3 checks per bit
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integer synd(M)
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real tov(3,N)
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real toc(7,M)
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real tanhtoc(7,M)
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real zn(N),zsum(N),zsave(N,3)
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real llr(N)
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real Tmn
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include "ldpc_174_91_c_reordered_parity.f90"
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include "ldpc_174_91_c_reordered_parity.f90"
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toc=0
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tov=0
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tanhtoc=0
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maxiterations=30
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nosd=0
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if(maxosd.gt.3) maxosd=3
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if(maxosd.eq.0) then ! osd with channel llrs
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nosd=1
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zsave(:,1)=llr
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elseif(maxosd.gt.0) then !
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nosd=maxosd
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elseif(maxosd.lt.0) then ! just bp
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nosd=0
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endif
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toc=0
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tov=0
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tanhtoc=0
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! initialize messages to checks
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do j=1,M
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do i=1,nrw(j)
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toc(i,j)=llr((Nm(i,j)))
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enddo
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enddo
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do j=1,M
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do i=1,nrw(j)
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toc(i,j)=llr((Nm(i,j)))
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enddo
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enddo
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ncnt=0
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nclast=0
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maxiterations=1
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zsum=0.0
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do isuper=1,maxsuper
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do iter=0,maxiterations
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ncnt=0
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nclast=0
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zsum=0.0
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do iter=0,maxiterations
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! Update bit log likelihood ratios (tov=0 in iteration 0).
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do i=1,N
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if( apmask(i) .ne. 1 ) then
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zn(i)=llr(i)+sum(tov(1:ncw,i))
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else
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zn(i)=llr(i)
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endif
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enddo
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zsum=zsum+zn
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do i=1,N
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if( apmask(i) .ne. 1 ) then
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zn(i)=llr(i)+sum(tov(1:ncw,i))
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else
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zn(i)=llr(i)
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endif
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enddo
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zsum=zsum+zn
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if(iter.gt.0 .and. iter.le.maxosd) then
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zsave(:,iter)=zsum
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endif
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! Check to see if we have a codeword (check before we do any iteration).
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cw=0
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where( zn .gt. 0. ) cw=1
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ncheck=0
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do i=1,M
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synd(i)=sum(cw(Nm(1:nrw(i),i)))
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if( mod(synd(i),2) .ne. 0 ) ncheck=ncheck+1
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! if( mod(synd(i),2) .ne. 0 ) write(*,*) 'check ',i,' unsatisfied'
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enddo
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! write(*,*) 'number of unsatisfied parity checks ',ncheck
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if( ncheck .eq. 0 ) then ! we have a codeword - if crc is good, return it
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m96=0
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m96(1:77)=cw(1:77)
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m96(83:96)=cw(78:91)
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call get_crc14(m96,96,nbadcrc)
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nharderror=count( (2*cw-1)*llr .lt. 0.0 )
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if(nbadcrc.eq.0) then
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message91=cw(1:91)
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dmin=0.0
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return
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endif
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endif
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cw=0
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where( zn .gt. 0. ) cw=1
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ncheck=0
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do i=1,M
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synd(i)=sum(cw(Nm(1:nrw(i),i)))
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if( mod(synd(i),2) .ne. 0 ) ncheck=ncheck+1
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enddo
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if( ncheck .eq. 0 ) then ! we have a codeword - if crc is good, return it
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m96=0
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m96(1:77)=cw(1:77)
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m96(83:96)=cw(78:91)
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call get_crc14(m96,96,nbadcrc)
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nharderror=count( (2*cw-1)*llr .lt. 0.0 )
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if(nbadcrc.eq.0) then
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message91=cw(1:91)
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hdec=0
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where(llr .ge. 0) hdec=1
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nxor=ieor(hdec,cw)
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dmin=sum(nxor*abs(llr))
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ntype=1
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return
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endif
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endif
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! if( iter.gt.0 ) then ! this code block implements an early stopping criterion
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if( iter.gt.10000 ) then ! this code block implements an early stopping criterion
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nd=ncheck-nclast
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if( nd .lt. 0 ) then ! # of unsatisfied parity checks decreased
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ncnt=0 ! reset counter
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else
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ncnt=ncnt+1
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endif
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if( iter.gt.0 ) then ! this code block implements an early stopping criterion
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! if( iter.gt.10000 ) then ! this code block implements an early stopping criterion
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nd=ncheck-nclast
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if( nd .lt. 0 ) then ! # of unsatisfied parity checks decreased
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ncnt=0 ! reset counter
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else
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ncnt=ncnt+1
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endif
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! write(*,*) iter,ncheck,nd,ncnt
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if( ncnt .ge. 5 .and. iter .ge. 10 .and. ncheck .gt. 15) then
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nharderror=-1
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return
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endif
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endif
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nclast=ncheck
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if( ncnt .ge. 5 .and. iter .ge. 10 .and. ncheck .gt. 15) then
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nharderror=-1
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exit
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endif
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endif
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nclast=ncheck
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! Send messages from bits to check nodes
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do j=1,M
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do i=1,nrw(j)
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ibj=Nm(i,j)
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toc(i,j)=zn(ibj)
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do kk=1,ncw ! subtract off what the bit had received from the check
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if( Mn(kk,ibj) .eq. j ) then
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toc(i,j)=toc(i,j)-tov(kk,ibj)
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endif
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do j=1,M
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do i=1,nrw(j)
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ibj=Nm(i,j)
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toc(i,j)=zn(ibj)
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do kk=1,ncw ! subtract off what the bit had received from the check
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if( Mn(kk,ibj) .eq. j ) then
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toc(i,j)=toc(i,j)-tov(kk,ibj)
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endif
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enddo
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enddo
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enddo
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enddo
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enddo
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! send messages from check nodes to variable nodes
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do i=1,M
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tanhtoc(1:7,i)=tanh(-toc(1:7,i)/2)
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enddo
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do i=1,M
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tanhtoc(1:7,i)=tanh(-toc(1:7,i)/2)
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enddo
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do j=1,N
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do i=1,ncw
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ichk=Mn(i,j) ! Mn(:,j) are the checks that include bit j
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Tmn=product(tanhtoc(1:nrw(ichk),ichk),mask=Nm(1:nrw(ichk),ichk).ne.j)
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call platanh(-Tmn,y)
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do j=1,N
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do i=1,ncw
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ichk=Mn(i,j) ! Mn(:,j) are the checks that include bit j
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Tmn=product(tanhtoc(1:nrw(ichk),ichk),mask=Nm(1:nrw(ichk),ichk).ne.j)
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call platanh(-Tmn,y)
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! y=atanh(-Tmn)
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tov(i,j)=2*y
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enddo
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enddo
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tov(i,j)=2*y
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enddo
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enddo
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enddo ! bp iterations
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enddo ! bp iterations
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call osd174_91(zsum,Keff,apmask,ndeep,message91,cw,nharderror,dminosd)
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if(nharderror.gt.0) then
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hdec=0
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where(llr .ge. 0) hdec=1
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nxor=ieor(hdec,cw)
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dmin=sum(nxor*abs(llr))
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return
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endif
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enddo ! super iterations
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do i=1,nosd
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zn=zsave(:,i)
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call osd174_91(zn,Keff,apmask,norder,message91,cw,nharderror,dminosd)
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if(nharderror.gt.0) then
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hdec=0
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where(llr .ge. 0) hdec=1
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nxor=ieor(hdec,cw)
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dmin=sum(nxor*abs(llr))
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ntype=2
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return
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endif
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enddo
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nharderror=-1
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ntype=0
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nharderror=-1
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dminosd=0.0
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return
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return
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end subroutine decode174_91
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@ -400,28 +400,23 @@ subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,nzhsym,lapon, &
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endif
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cw=0
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call timer('bpd174_91 ',0)
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call bpdecode174_91(llrz,apmask,max_iterations,message77,cw,nharderrors, &
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niterations,ncheck)
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call timer('bpd174_91 ',1)
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dmin=0.0
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if(nharderrors.lt.0 .and. ncheck.le.30 .and. ndepth.ge.2) then
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! ndeep=ndepth
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ndeep=ndepth-1
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if(abs(nfqso-f1).le.napwid .or. abs(nftx-f1).le.napwid .or. ncontest.eq.7) then
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! ndeep=4
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ndeep=3
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endif
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! if(nagain) ndeep=5
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if(nagain) ndeep=4
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call timer('osd174_91 ',0)
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Keff=91
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! call osd174_91(llrz,Keff,apmask,ndeep,message91,cw,nharderrors,dmin)
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maxsuper=1
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call decode174_91(llrz,Keff,ndeep,apmask,maxsuper,message91,cw,nharderrors,niterations,ncheck,dmin)
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if(nharderrors.ge.0) message77=message91(1:77)
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call timer('osd174_91 ',1)
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norder=2
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maxosd=2
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if(ndepth.lt.3) maxosd=1
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if(abs(nfqso-f1).le.napwid .or. abs(nftx-f1).le.napwid .or. ncontest.eq.7) then
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maxosd=2
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endif
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if(nagain) then
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norder=3
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maxosd=1
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endif
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call timer('dec174_91 ',0)
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Keff=91
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call decode174_91(llrz,Keff,maxosd,norder,apmask,message91,cw, &
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ntype,nharderrors,dmin)
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if(nharderrors.ge.0) message77=message91(1:77)
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call timer('dec174_91 ',1)
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msg37=' '
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if(nharderrors.lt.0 .or. nharderrors.gt.36) cycle
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