Reconfigure simulator for short message tests.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6993 ab8295b8-cf94-4d9e-aec4-7959e3be5d79

lib/ldpcsim.f90

@@ -1,29 +1,21 @@
 program ldpcsim
 
-! simulate with packed 72-bit messages and 8-bit hash - so only makes
-! sense to use this with codes having K=80.
-
 use, intrinsic :: iso_c_binding
 use hashing
 use packjt
 
 character*22 msg,msgsent,msgreceived
-integer*4 i4Msg6BitWords(12),i4Dec6BitWords(12)
-integer*1, target:: i1Msg8BitBytes(10) ! 72 bit msg + 8 bit hash
-integer*1, target:: i1Dec8BitBytes(10) ! 72 bit msg + 8 bit hash
-integer*1 i1hashdec
 character*80 prefix
 character*85 pchk_file,gen_file
 character*8 arg
 integer*1, allocatable ::  codeword(:), decoded(:), message(:)
 real*8, allocatable ::  lratio(:), rxdata(:)
-integer*1 i1hash(4),i1
-equivalence (ihash,i1hash)
+integer ihash
 
 nargs=iargc()
 if(nargs.ne.7) then
    print*,'Usage: ldpcsim  <pchk file prefix      >  N   K  niter ndither #trials  s '
-   print*,'eg:    ldpcsim  "/pathto/128-80-peg-reg3" 128 80  10     1     1000    0.75'
+   print*,'eg:    ldpcsim  "/pathto/peg-32-16-reg3"  32  16  10     1     1000    0.75'
    return
 endif
 call getarg(1,prefix)
@@ -43,9 +35,10 @@ read(arg,*) s
 pchk_file=trim(prefix)//".pchk"
 gen_file=trim(prefix)//".gen"
 
-! rate=real(K)/real(N)
+rate=real(K)/real(N)
+write(*,*) "rate: ",rate
 ! don't count hash bits as data bits
-rate=72.0/real(N)
+!rate=5.0/real(N)
 
 write(*,*) "pchk file: ",pchk_file
 write(*,*) "niter= ",max_iterations," ndither= ",max_dither," s= ",s
@@ -54,59 +47,34 @@ allocate ( codeword(N), decoded(K), message(K) )
 allocate ( lratio(N), rxdata(N) )
 call init_ldpc(trim(pchk_file)//char(0),trim(gen_file)//char(0))
 
-msg="123"
-call fmtmsg(msg,iz)
-call packmsg(msg,i4Msg6BitWords,itype)
-call unpackmsg(i4Msg6BitWords,msgsent)
-write(*,*) "Message: ",msgsent
+msg="K9AN K1JT RRR"
+irpt=62
+call hash(msg,22,ihash)
+ihash=iand(ihash,1023)                 !10-bit hash
+ig=64*ihash + irpt                     !6-bit report
+write(*,*) irpt,ihash,ig
 
-! Convert from 12 6-bit words to 10 8-bit words
-i4=0
-ik=0
-im=0
-do i=1,12
-  nn=i4Msg6BitWords(i)
-  do j=1, 6
-    ik=ik+1
-    i4=i4+i4+iand(1,ishft(nn,j-6))
-    i4=iand(i4,255)
-    if(ik.eq.8) then
-      im=im+1
-!      if(i4.gt.127) i4=i4-256
-      i1Msg8BitBytes(im)=i4
-      ik=0
-    endif
-  enddo
-enddo
-ihash=nhash(c_loc(i1Msg8BitBytes),int(9,c_size_t),146)
-ihash=2*iand(ihash,255)
-i1Msg8BitBytes(10)=i1hash(1)
-
-mbit=0
-do i=1, 10
-  i1=i1Msg8BitBytes(i)
-  do ibit=1,8
-    mbit=mbit+1
-    message(mbit)=iand(1,ishft(i1,ibit-8))
-  enddo
+do i=1,16
+  message(i)=iand(1,ishft(ig,1-i))
 enddo
 
 call ldpc_encode(message,codeword)
+call init_random_seed()
 
 write(*,*) "Eb/N0   ngood  nundetected nbadhash"
-do idb = 0, 11
-  db=idb/2.0-0.5
+do idb = -6, 14
+  db=idb/2.0-1.0
   sigma=1/sqrt( 2*rate*(10**(db/10.0)) )
-
   ngood=0
   nue=0
   nbadhash=0
 
   do itrial=1, ntrials
-
+call sgran()
 ! Create a realization of a noisy received word
     do i=1,N
       rxdata(i) = 2.0*(codeword(i)-0.5) + sigma*gran()
+!write(*,*) i,gran()
     enddo
 
 ! Correct signal normalization is important for this decoder.
@@ -114,45 +82,35 @@ do idb = 0, 11
     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 .le. 0 ) then
+      ss=sigma
+    else 
+      ss=s
+    endif
+
     do i=1,N
-      if( s .le. 0 ) then
-        ss=sigma
-      else 
-        ss=s
-      endif
       lratio(i)=exp(2.0*rxdata(i)/(ss*ss))
     enddo
 
 ! max_iterations is max number of belief propagation iterations
     call ldpc_decode(lratio, decoded, max_iterations, niterations, max_dither, ndither)
-
 ! If the decoder finds a valid codeword, niterations will be .ge. 0.
     if( niterations .ge. 0 ) then
       nueflag=0
       nhashflag=0
 
-! The decoder found a codeword. Compare received hash (byte 10) with computed hash.
-! Collapse 80 decoded bits to 10 bytes. Bytes 1-9 are the message, byte 10 is the hash.
-      do ibyte=1,10
-        itmp=0
-        do ibit=1,8
-          itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*8+ibit)) 
-        enddo
-        i1Dec8BitBytes(ibyte)=itmp
+      imsg=0
+      do i=1,16
+        imsg=ishft(imsg,1)+iand(1,decoded(17-i))
       enddo
+      nrxrpt=iand(imsg,63)
+      nrxhash=(imsg-nrxrpt)/64
 
-! Calculate the hash using the first 9 bytes.
-      ihashdec=nhash(c_loc(i1Dec8BitBytes),int(9,c_size_t),146)
-      ihashdec=2*iand(ihashdec,255)
-
-! Compare calculated hash with received byte 10 - if they agree, keep the message.
-      i1hashdec=ihashdec
-      if( i1hashdec .ne. i1Dec8BitBytes(10) ) then
+      if( nrxhash .ne. ihash ) then
         nbadhash=nbadhash+1
         nhashflag=1   
       endif
@@ -166,21 +124,6 @@ do idb = 0, 11
 
       if( nhashflag .eq. 0 .and. nueflag .eq. 0 ) then
         ngood=ngood+1
-
-! don't bother to unpack while testing
-if( .false. ) then
-! unpack 72-bit message
-        do ibyte=1,12
-          itmp=0
-          do ibit=1,6
-            itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*6+ibit))
-          enddo
-          i4Dec6BitWords(ibyte)=itmp
-        enddo
-        call unpackmsg(i4Dec6BitWords,msgreceived)
-        print*,"Received ",msgreceived
-endif
-
       else if( nhashflag .eq. 0 .and. nueflag .eq. 1 ) then
         nue=nue+1;
       endif