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Streamline decoding to use a single call to decode174_91.

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This commit is contained in:
Steven Franke 2020-05-05 11:59:43 -05:00
parent 27b94e2cc7
commit 9b6dd092c5
4 changed files with 167 additions and 168 deletions
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14
lib/fsk4hf/ldpcsim174_91.f90
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@ -105,19 +105,9 @@ program ldpcsim174_91
llr(1:nap)=5*(2.0*msgbits(1:nap)-1.0) llr(1:nap)=5*(2.0*msgbits(1:nap)-1.0)
apmask=0 apmask=0
apmask(1:nap)=1 apmask(1:nap)=1
! max_iterations is max number of belief propagation iterations call decode174_91(llr,Keff,nbposd,ndepth,apmask,message91,cw,ntype,nharderrors,dmin)
call bpdecode174_91(llr, apmask, max_iterations, message77, cw, nhardbp,niterations,ncheck)
if( ndepth .ge. 0 .and. nhardbp .lt. 0 ) then
dmin=0.0
if(nbposd.eq.0) then
call osd174_91(llr,Keff,apmask,ndepth,message91,cw,nhardosd,dmin)
elseif(nbposd.gt.0) then
maxsuper=nbposd
call decode174_91(llr,Keff,ndepth,apmask,maxsuper,message91,cw,nhardosd,niterations,ncheck,dmin)
endif
! If the decoder finds a valid codeword, nharderrors will be .ge. 0. ! If the decoder finds a valid codeword, nharderrors will be .ge. 0.
endif if( nharderrors.ge.0 ) then
if( nhardbp .ge. 0 .or. nhardosd.ge.0 ) then
nhw=count(cw.ne.codeword) nhw=count(cw.ne.codeword)
if(nhw.eq.0) then ! this is a good decode if(nhw.eq.0) then ! this is a good decode
ngood=ngood+1 ngood=ngood+1

30
lib/ft4_decode.f90
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@ -407,27 +407,19 @@ contains
endif endif
message77=0 message77=0
dmin=0.0 dmin=0.0
call timer('bpdec174',0)
call bpdecode174_91(llr,apmask,max_iterations,message77, &
cw,nharderror,niterations,ncheck)
call timer('bpdec174',1)
if(doosd .and. nharderror.lt.0) then ndeep=2
! ndeep=3 maxosd=1
ndeep=2 if(abs(nfqso-f1).le.napwid) then
if(abs(nfqso-f1).le.napwid) then maxosd=2
! ndeep=4
ndeep=3
endif
call timer('osd174_91 ',0)
Keff=91
maxsuper=1
! call osd174_91(llr,Keff,apmask,ndeep,message91,cw,nharderror,dmin)
call decode174_91(llr,Keff,ndeep,apmask,maxsuper,message91,cw,nharderror, &
niterations,ncheck,dmin)
message77=message91(1:77)
call timer('osd174_91 ',1)
endif endif
if(.not.doosd) maxosd = -1
call timer('dec174_91 ',0)
Keff=91
call decode174_91(llr,Keff,maxosd,ndeep,apmask,message91,cw, &
ntype,nharderror,dmin)
message77=message91(1:77)
call timer('dec174_91 ',1)
if(sum(message77).eq.0) cycle if(sum(message77).eq.0) cycle
if( nharderror.ge.0 ) then if( nharderror.ge.0 ) then

242
lib/ft8/decode174_91.f90
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@ -1,133 +1,155 @@
subroutine decode174_91(llr,Keff,ndeep,apmask,maxsuper,message91,cw,nharderror,iter,ncheck,dmin) subroutine decode174_91(llr,Keff,maxosd,norder,apmask,message91,cw,ntype,nharderror,dmin)
! !
! A hybrid bp/osd decoder for the (174,91) code. ! A hybrid bp/osd decoder for the (174,91) code.
! !
integer, parameter:: N=174, K=91, M=N-K ! maxosd<0: do bp only
integer*1 cw(N),apmask(N) ! maxosd=0: do bp and then call osd once with channel llrs
integer*1 nxor(N),hdec(N) ! maxosd>1: do bp and then call osd maxosd times with saved bp outputs
integer*1 message91(91),m96(96) ! norder : osd decoding depth
integer nrw(M),ncw !
integer Nm(7,M) integer, parameter:: N=174, K=91, M=N-K
integer Mn(3,N) ! 3 checks per bit integer*1 cw(N),apmask(N)
integer synd(M) integer*1 nxor(N),hdec(N)
real tov(3,N) integer*1 message91(91),m96(96)
real toc(7,M) integer nrw(M),ncw
real tanhtoc(7,M) integer Nm(7,M)
real zn(N),zsum(N) integer Mn(3,N) ! 3 checks per bit
real llr(N) integer synd(M)
real Tmn real tov(3,N)
real toc(7,M)
real tanhtoc(7,M)
real zn(N),zsum(N),zsave(N,3)
real llr(N)
real Tmn
include "ldpc_174_91_c_reordered_parity.f90" include "ldpc_174_91_c_reordered_parity.f90"
toc=0 maxiterations=30
tov=0 nosd=0
tanhtoc=0 if(maxosd.gt.3) maxosd=3
if(maxosd.eq.0) then ! osd with channel llrs
nosd=1
zsave(:,1)=llr
elseif(maxosd.gt.0) then !
nosd=maxosd
elseif(maxosd.lt.0) then ! just bp
nosd=0
endif
toc=0
tov=0
tanhtoc=0
! initialize messages to checks ! initialize messages to checks
do j=1,M do j=1,M
do i=1,nrw(j) do i=1,nrw(j)
toc(i,j)=llr((Nm(i,j))) toc(i,j)=llr((Nm(i,j)))
enddo enddo
enddo enddo
ncnt=0 ncnt=0
nclast=0 nclast=0
zsum=0.0
maxiterations=1 do iter=0,maxiterations
zsum=0.0
do isuper=1,maxsuper
do iter=0,maxiterations
! Update bit log likelihood ratios (tov=0 in iteration 0). ! Update bit log likelihood ratios (tov=0 in iteration 0).
do i=1,N do i=1,N
if( apmask(i) .ne. 1 ) then if( apmask(i) .ne. 1 ) then
zn(i)=llr(i)+sum(tov(1:ncw,i)) zn(i)=llr(i)+sum(tov(1:ncw,i))
else else
zn(i)=llr(i) zn(i)=llr(i)
endif endif
enddo enddo
zsum=zsum+zn zsum=zsum+zn
if(iter.gt.0 .and. iter.le.maxosd) then
zsave(:,iter)=zsum
endif
! Check to see if we have a codeword (check before we do any iteration). ! Check to see if we have a codeword (check before we do any iteration).
cw=0 cw=0
where( zn .gt. 0. ) cw=1 where( zn .gt. 0. ) cw=1
ncheck=0 ncheck=0
do i=1,M do i=1,M
synd(i)=sum(cw(Nm(1:nrw(i),i))) synd(i)=sum(cw(Nm(1:nrw(i),i)))
if( mod(synd(i),2) .ne. 0 ) ncheck=ncheck+1 if( mod(synd(i),2) .ne. 0 ) ncheck=ncheck+1
! if( mod(synd(i),2) .ne. 0 ) write(*,*) 'check ',i,' unsatisfied' enddo
enddo if( ncheck .eq. 0 ) then ! we have a codeword - if crc is good, return it
! write(*,*) 'number of unsatisfied parity checks ',ncheck m96=0
if( ncheck .eq. 0 ) then ! we have a codeword - if crc is good, return it m96(1:77)=cw(1:77)
m96=0 m96(83:96)=cw(78:91)
m96(1:77)=cw(1:77) call get_crc14(m96,96,nbadcrc)
m96(83:96)=cw(78:91) nharderror=count( (2*cw-1)*llr .lt. 0.0 )
call get_crc14(m96,96,nbadcrc) if(nbadcrc.eq.0) then
nharderror=count( (2*cw-1)*llr .lt. 0.0 ) message91=cw(1:91)
if(nbadcrc.eq.0) then hdec=0
message91=cw(1:91) where(llr .ge. 0) hdec=1
dmin=0.0 nxor=ieor(hdec,cw)
return dmin=sum(nxor*abs(llr))
endif ntype=1
endif return
endif
endif
! if( iter.gt.0 ) then ! this code block implements an early stopping criterion if( iter.gt.0 ) then ! this code block implements an early stopping criterion
if( iter.gt.10000 ) then ! this code block implements an early stopping criterion ! if( iter.gt.10000 ) then ! this code block implements an early stopping criterion
nd=ncheck-nclast nd=ncheck-nclast
if( nd .lt. 0 ) then ! # of unsatisfied parity checks decreased if( nd .lt. 0 ) then ! # of unsatisfied parity checks decreased
ncnt=0 ! reset counter ncnt=0 ! reset counter
else else
ncnt=ncnt+1 ncnt=ncnt+1
endif endif
! write(*,*) iter,ncheck,nd,ncnt ! write(*,*) iter,ncheck,nd,ncnt
if( ncnt .ge. 5 .and. iter .ge. 10 .and. ncheck .gt. 15) then if( ncnt .ge. 5 .and. iter .ge. 10 .and. ncheck .gt. 15) then
nharderror=-1 nharderror=-1
exit
return endif
endif endif
endif nclast=ncheck
nclast=ncheck
! Send messages from bits to check nodes ! Send messages from bits to check nodes
do j=1,M do j=1,M
do i=1,nrw(j) do i=1,nrw(j)
ibj=Nm(i,j) ibj=Nm(i,j)
toc(i,j)=zn(ibj) toc(i,j)=zn(ibj)
do kk=1,ncw ! subtract off what the bit had received from the check do kk=1,ncw ! subtract off what the bit had received from the check
if( Mn(kk,ibj) .eq. j ) then if( Mn(kk,ibj) .eq. j ) then
toc(i,j)=toc(i,j)-tov(kk,ibj) toc(i,j)=toc(i,j)-tov(kk,ibj)
endif endif
enddo
enddo
enddo enddo
enddo
enddo
! send messages from check nodes to variable nodes ! send messages from check nodes to variable nodes
do i=1,M do i=1,M
tanhtoc(1:7,i)=tanh(-toc(1:7,i)/2) tanhtoc(1:7,i)=tanh(-toc(1:7,i)/2)
enddo enddo
do j=1,N do j=1,N
do i=1,ncw do i=1,ncw
ichk=Mn(i,j) ! Mn(:,j) are the checks that include bit j ichk=Mn(i,j) ! Mn(:,j) are the checks that include bit j
Tmn=product(tanhtoc(1:nrw(ichk),ichk),mask=Nm(1:nrw(ichk),ichk).ne.j) Tmn=product(tanhtoc(1:nrw(ichk),ichk),mask=Nm(1:nrw(ichk),ichk).ne.j)
call platanh(-Tmn,y) call platanh(-Tmn,y)
! y=atanh(-Tmn) ! y=atanh(-Tmn)
tov(i,j)=2*y tov(i,j)=2*y
enddo enddo
enddo enddo
enddo ! bp iterations enddo ! bp iterations
call osd174_91(zsum,Keff,apmask,ndeep,message91,cw,nharderror,dminosd) do i=1,nosd
if(nharderror.gt.0) then zn=zsave(:,i)
hdec=0 call osd174_91(zn,Keff,apmask,norder,message91,cw,nharderror,dminosd)
where(llr .ge. 0) hdec=1 if(nharderror.gt.0) then
nxor=ieor(hdec,cw) hdec=0
dmin=sum(nxor*abs(llr)) where(llr .ge. 0) hdec=1
return nxor=ieor(hdec,cw)
endif dmin=sum(nxor*abs(llr))
enddo ! super iterations ntype=2
return
endif
enddo
nharderror=-1 ntype=0
nharderror=-1
dminosd=0.0
return return
end subroutine decode174_91 end subroutine decode174_91

35
lib/ft8/ft8b.f90
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@ -400,28 +400,23 @@ subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,nzhsym,lapon, &
endif endif
cw=0 cw=0
call timer('bpd174_91 ',0)
call bpdecode174_91(llrz,apmask,max_iterations,message77,cw,nharderrors, &
niterations,ncheck)
call timer('bpd174_91 ',1)
dmin=0.0 dmin=0.0
if(nharderrors.lt.0 .and. ncheck.le.30 .and. ndepth.ge.2) then norder=2
! ndeep=ndepth maxosd=2
ndeep=ndepth-1 if(ndepth.lt.3) maxosd=1
if(abs(nfqso-f1).le.napwid .or. abs(nftx-f1).le.napwid .or. ncontest.eq.7) then if(abs(nfqso-f1).le.napwid .or. abs(nftx-f1).le.napwid .or. ncontest.eq.7) then
! ndeep=4 maxosd=2
ndeep=3
endif
! if(nagain) ndeep=5
if(nagain) ndeep=4
call timer('osd174_91 ',0)
Keff=91
! call osd174_91(llrz,Keff,apmask,ndeep,message91,cw,nharderrors,dmin)
maxsuper=1
call decode174_91(llrz,Keff,ndeep,apmask,maxsuper,message91,cw,nharderrors,niterations,ncheck,dmin)
if(nharderrors.ge.0) message77=message91(1:77)
call timer('osd174_91 ',1)
endif endif
if(nagain) then
norder=3
maxosd=1
endif
call timer('dec174_91 ',0)
Keff=91
call decode174_91(llrz,Keff,maxosd,norder,apmask,message91,cw, &
ntype,nharderrors,dmin)
if(nharderrors.ge.0) message77=message91(1:77)
call timer('dec174_91 ',1)
msg37=' ' msg37=' '
if(nharderrors.lt.0 .or. nharderrors.gt.36) cycle if(nharderrors.lt.0 .or. nharderrors.gt.36) cycle