From 8da98fee1e7cdb32ec9fccccd055405fd752d2d4 Mon Sep 17 00:00:00 2001 From: Steven Franke Date: Tue, 21 Apr 2020 15:02:57 -0500 Subject: [PATCH] Cleanup --- lib/fsk4hf/decode174_74.f90 | 224 ++++++++++++++++++------------------ 1 file changed, 112 insertions(+), 112 deletions(-) diff --git a/lib/fsk4hf/decode174_74.f90 b/lib/fsk4hf/decode174_74.f90 index d4ed89edd..9d8020de2 100644 --- a/lib/fsk4hf/decode174_74.f90 +++ b/lib/fsk4hf/decode174_74.f90 @@ -2,127 +2,127 @@ subroutine decode174_74(llr,Keff,ndeep,apmask,maxsuper,message74,cw,nharderror,i ! ! A hybrid bp/osd decoder for the (174,74) code. ! -integer, parameter:: N=174, K=74, M=N-K -integer*1 cw(N),apmask(N) -integer*1 decoded(K) -integer*1 message74(74) -integer nrw(M),ncw -integer Nm(6,M) -integer Mn(3,N) ! 3 checks per bit -integer synd(M) -real tov(3,N) -real toc(6,M) -real tanhtoc(6,M) -real zn(N),zsum(N) -real llr(N) -real Tmn + integer, parameter:: N=174, K=74, M=N-K + integer*1 cw(N),apmask(N) + integer*1 decoded(K) + integer*1 message74(74) + integer nrw(M),ncw + integer Nm(6,M) + integer Mn(3,N) ! 3 checks per bit + integer synd(M) + real tov(3,N) + real toc(6,M) + real tanhtoc(6,M) + real zn(N),zsum(N) + real llr(N) + real Tmn -include "ldpc_174_74_parity.f90" + include "ldpc_174_74_parity.f90" -decoded=0 -toc=0 -tov=0 -tanhtoc=0 + decoded=0 + toc=0 + tov=0 + tanhtoc=0 ! initialize messages to checks -do j=1,M - do i=1,nrw(j) - toc(i,j)=llr((Nm(i,j))) - enddo -enddo - -ncnt=0 -nclast=0 - -maxiterations=1 - -zsum=0.0 -do isuper=1,maxsuper - -do iter=0,maxiterations -! Update bit log likelihood ratios (tov=0 in iteration 0). - do i=1,N - if( apmask(i) .ne. 1 ) then - zn(i)=llr(i)+sum(tov(1:ncw,i)) - else - zn(i)=llr(i) - endif - enddo -zsum=zsum+zn -! Check to see if we have a codeword (check before we do any iteration). - cw=0 - where( zn .gt. 0. ) cw=1 - ncheck=0 - do i=1,M - 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 ) write(*,*) 'check ',i,' unsatisfied' - enddo -! write(*,*) 'number of unsatisfied parity checks ',ncheck - if( ncheck .eq. 0 ) then ! we have a codeword - if crc is good, return it - decoded=cw(1:K) - call get_crc24(decoded,74,nbadcrc) - nharderror=count( (2*cw-1)*llr .lt. 0.0 ) - if(nbadcrc.eq.0) then - message74=decoded(1:74) -dmin=0.0 - return - endif - endif - -! 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 - nd=ncheck-nclast - if( nd .lt. 0 ) then ! # of unsatisfied parity checks decreased - ncnt=0 ! reset counter - else - ncnt=ncnt+1 - endif -! write(*,*) iter,ncheck,nd,ncnt - if( ncnt .ge. 5 .and. iter .ge. 10 .and. ncheck .gt. 15) then - nharderror=-1 - - return - endif - endif - nclast=ncheck - -! Send messages from bits to check nodes - do j=1,M - do i=1,nrw(j) - ibj=Nm(i,j) - toc(i,j)=zn(ibj) - do kk=1,ncw ! subtract off what the bit had received from the check - if( Mn(kk,ibj) .eq. j ) then - toc(i,j)=toc(i,j)-tov(kk,ibj) - endif + do j=1,M + do i=1,nrw(j) + toc(i,j)=llr((Nm(i,j))) enddo - enddo - enddo + enddo + + ncnt=0 + nclast=0 + + maxiterations=1 + + zsum=0.0 + do isuper=1,maxsuper + + do iter=0,maxiterations +! Update bit log likelihood ratios (tov=0 in iteration 0). + do i=1,N + if( apmask(i) .ne. 1 ) then + zn(i)=llr(i)+sum(tov(1:ncw,i)) + else + zn(i)=llr(i) + endif + enddo + zsum=zsum+zn +! Check to see if we have a codeword (check before we do any iteration). + cw=0 + where( zn .gt. 0. ) cw=1 + ncheck=0 + do i=1,M + 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 ) write(*,*) 'check ',i,' unsatisfied' + enddo +! write(*,*) 'number of unsatisfied parity checks ',ncheck + if( ncheck .eq. 0 ) then ! we have a codeword - if crc is good, return it + decoded=cw(1:K) + call get_crc24(decoded,74,nbadcrc) + nharderror=count( (2*cw-1)*llr .lt. 0.0 ) + if(nbadcrc.eq.0) then + message74=decoded(1:74) + dmin=0.0 + return + endif + endif + +! 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 + nd=ncheck-nclast + if( nd .lt. 0 ) then ! # of unsatisfied parity checks decreased + ncnt=0 ! reset counter + else + ncnt=ncnt+1 + endif +! write(*,*) iter,ncheck,nd,ncnt + if( ncnt .ge. 5 .and. iter .ge. 10 .and. ncheck .gt. 15) then + nharderror=-1 + + return + endif + endif + nclast=ncheck + +! Send messages from bits to check nodes + do j=1,M + do i=1,nrw(j) + ibj=Nm(i,j) + toc(i,j)=zn(ibj) + do kk=1,ncw ! subtract off what the bit had received from the check + if( Mn(kk,ibj) .eq. j ) then + toc(i,j)=toc(i,j)-tov(kk,ibj) + endif + enddo + enddo + enddo ! send messages from check nodes to variable nodes - do i=1,M - tanhtoc(1:6,i)=tanh(-toc(1:6,i)/2) - enddo + do i=1,M + tanhtoc(1:6,i)=tanh(-toc(1:6,i)/2) + enddo - do j=1,N - do i=1,ncw - 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) - call platanh(-Tmn,y) + do j=1,N + do i=1,ncw + 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) + call platanh(-Tmn,y) ! y=atanh(-Tmn) - tov(i,j)=2*y - enddo - enddo + tov(i,j)=2*y + enddo + enddo -enddo ! bp iterations -llr=zsum - call osd174_74(llr,Keff,apmask,ndeep,message74,cw,nharderror,dmin) - if(nharderror.gt.0) then - return - endif -enddo ! super iterations + enddo ! bp iterations + llr=zsum + call osd174_74(llr,Keff,apmask,ndeep,message74,cw,nharderror,dmin) + if(nharderror.gt.0) then + return + endif + enddo ! super iterations -nharderror=-1 + nharderror=-1 -return + return end subroutine decode174_74