Merge branch 'develop' of bitbucket.org:k1jt/wsjtx into develop

CMakeLists.txt

@@ -602,7 +602,7 @@ set (wsjt_FSRCS
   lib/fsk4hf/osd204.f90
   lib/fsk4hf/genwsprcpm.f90
   lib/fsk4hf/encode204.f90
-#  lib/ft8/decode174_91.f90
+  lib/fsk4hf/decode174_74.f90
   lib/fsk4hf/ldpcsim174_91.f90
   lib/fsk4hf/ldpcsim174_74.f90
   lib/fsk4hf/ldpcsim174_101.f90

lib/fsk4hf/decode174_74.f90

@@ -0,0 +1,128 @@
+subroutine decode174_74(llr,Keff,ndeep,apmask,maxsuper,message74,cw,nharderror,iter,ncheck,dmin,isuper)
+!
+! 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
+
+include "ldpc_174_74_parity.f90"
+
+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
+      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 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
+
+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
+
+return
+end subroutine decode174_74

lib/fsk4hf/ldpcsim174_74.f90

@@ -98,10 +98,6 @@ program ldpcsim174_74
          rx2av=sum(rxdata*rxdata)/N
          rxsig=sqrt(rx2av-rxav*rxav)
          rxdata=rxdata/rxsig
-! To match the metric to the channel, s should be set to the noise standard deviation.
-! For now, set s to the value that optimizes decode probability near threshold.
-! The s parameter can be tuned to trade a few tenth's dB of threshold for an order of
-! magnitude in UER
          if( s .lt. 0 ) then
             ss=sigma
          else
@@ -114,7 +110,8 @@ program ldpcsim174_74
          call bpdecode174_74(llr,apmask,max_iterations,message,cw,nharderror,niterations)
          dmin=0.0
          if( (nharderror .lt. 0) .and. (ndeep .ge. 0) ) then
-            call osd174_74(llr, Keff, apmask, ndeep, message, cw, nharderror, dmin)
+!            call osd174_74(llr, Keff, apmask, ndeep, message, cw, nharderror, dmin)
+call decode174_74(llr,Keff,ndeep,apmask,max_iterations,message,cw,nharderror,niterations,ncheck,dmin,isuper)
          endif
 
          if(nharderror.ge.0) then

lib/fsk4hf/osd174_74.f90

@@ -22,7 +22,7 @@ subroutine osd174_74(llr,k,apmask,ndeep,message74,cw,nhardmin,dmin)
    integer indices(N),nxor(N)
    integer*1 cw(N),ce(N),c0(N),hdec(N)
    integer*1, allocatable :: decoded(:)
-   integer*1 message50(50),message74(74)
+   integer*1 message74(74)
    integer indx(N)
    real llr(N),rx(N),absrx(N)
 

lib/fsk4hf/wspr4d.f90

@@ -119,13 +119,13 @@ program wspr4d
          enddo
 
          if(smax .lt. 100.0 ) cycle
+
          idecoded=0
-         do ijitter=0,4
+         do ijitter=0,2
             if(idecoded.eq.1) exit
-            if(ijitter.eq.1) ioffset=20
+            if(ijitter.eq.0) ioffset=0
-            if(ijitter.eq.2) ioffset=-20
+            if(ijitter.eq.1) ioffset=50
-            if(ijitter.eq.3) ioffset=40
+            if(ijitter.eq.2) ioffset=-50
-            if(ijitter.eq.4) ioffset=-40
             is0=isbest+ioffset
             if(is0.lt.0) cycle
             cframe=c2(is0:is0+103*416-1)
@@ -168,7 +168,13 @@ program wspr4d
                dmin=0.0
                call bpdecode174_74(llr,apmask,max_iterations,message,cw,nhardbp,niterations)
                Keff=64
-               if(nhardbp.lt.0) call osd174_74(llr,Keff,apmask,5,message,cw,nhardosd,dmin)
+!               if(nhardbp.lt.0) call osd174_74(llr,Keff,apmask,5,message,cw,nhardosd,dmin)
+               maxsuperits=2
+               ndeep=4 
+               if(nhardbp.lt.0) then
+                  call decode174_74(llr,Keff,ndeep,apmask,maxsuperits,message,cw,nhardosd,iter,ncheck,dmin,isuper)
+               endif
+
                if(nhardbp.ge.0 .or. nhardosd.ge.0) then
                   write(c77,'(50i1)') message
                   c77(51:77)='000000000000000000000110000'