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https://github.com/saitohirga/WSJT-X.git
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109 lines
3.4 KiB
Fortran
109 lines
3.4 KiB
Fortran
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subroutine gf64_osd(mrsym,mrprob,mr2sym,mr2prob,cw)
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use jt65_generator_matrix
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integer mrsym(63),mrprob(63),mr2sym(63),mr2prob(63),cw(63)
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integer indx(63)
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integer gmrb(12,63)
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integer correct(63)
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integer correctr(63)
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integer candidate(63)
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integer candidater(63)
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logical mask(63)
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data correct/ & ! K1ABC W9XYZ EN37
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41, 0, 54, 46, 55, 29, 57, 35, 35, 48, 48, 61, &
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21, 58, 25, 10, 50, 43, 28, 37, 10, 2, 61, 55, &
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25, 5, 5, 57, 28, 11, 32, 45, 16, 55, 31, 46, &
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44, 55, 34, 38, 50, 62, 52, 58, 17, 62, 35, 34, &
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28, 21, 15, 47, 33, 20, 15, 28, 58, 4, 58, 61, &
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59, 42, 2/
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correctr=correct(63:1:-1)
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call indexx(mrprob,63,indx)
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! do i=1,63
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! write(*,*) i,correctr(indx(i)),mrsym(indx(i)),mr2sym(indx(i))
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! enddo
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nhard=count(mrsym.ne.correctr)
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nerrtop12=count(mrsym(indx(52:63)).ne.correctr(indx(52:63)))
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nerrnext12=count(mrsym(indx(40:51)).ne.correctr(indx(40:51)))
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write(*,*) 'nerr, nerrtop12, nerrnext12 ',nerr,nerrtop12,nerrnext12
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! The best 12 symbols will be used as the Most Reliable Basis
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! Reorder the columns of the generator matrix in order of decreasing quality.
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do i=1,63
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gmrb(:,i)=g(:,indx(63+1-i))
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enddo
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! Put the generator matrix in standard form so that top 12 symbols are
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! encoded systematically.
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call gf64_standardize_genmat(gmrb)
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! Add various error patterns to the 12 basis symbols and reencode each one
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! to get a list of codewords. For now, just find the zero'th order codeword.
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call gf64_encode(gmrb,mrsym(indx(63:52:-1)),candidate)
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! Undo the sorting to put the codeword symbols back into the "right" order.
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candidater=candidate(63:1:-1)
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candidate(indx)=candidater
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!write(*,'(63i3)') candidate
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!write(*,'(63i3)') correctr
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!write(*,'(63i3)') mrsym
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nerr=count(correctr.ne.candidate)
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write(*,*) 'Number of differences between candidate and correct codeword: ',nerr
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if( nerr .eq. 0 ) write(*,*) 'Successful decode'
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return
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end subroutine gf64_osd
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subroutine gf64_standardize_genmat(gmrb)
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use gf64math
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integer gmrb(12,63),temp(63),gkk,gjk,gkkinv
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do k=1,12
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gkk=gmrb(k,k)
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if(gkk.eq.0) then ! zero pivot - swap with the first row with nonzero value
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do kk=k+1,12
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if(gmrb(kk,k).ne.0) then
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temp=gmrb(k,:)
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gmrb(k,:)=gmrb(kk,:)
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gmrb(kk,:)=temp
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gkk=gmrb(k,k)
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goto 20
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endif
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enddo
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endif
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20 gkkinv=gf64_inverse(gkk)
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do ic=1,63
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gmrb(k,ic)=gf64_product(gmrb(k,ic),gkkinv)
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enddo
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do j=1,12
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if(j.ne.k) then
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gjk=gmrb(j,k)
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do ic=1,63
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gmrb(j,ic)=gf64_sum(gmrb(j,ic),gf64_product(gmrb(k,ic),gjk))
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enddo
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endif
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enddo
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enddo
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return
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end subroutine gf64_standardize_genmat
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subroutine gf64_encode(gg,message,codeword)
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!
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! Encoder for a (63,12) Reed-Solomon code.
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! The generator matrix is supplied in array gg.
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!
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use gf64math
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integer message(12) !Twelve 6-bit data symbols
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integer codeword(63) !RS(63,12) codeword
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integer gg(12,63)
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codeword=0
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do j=1,12
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do i=1,63
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iprod=gf64_product(message(j),gg(j,i))
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codeword(i)=gf64_sum(codeword(i),iprod)
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enddo
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enddo
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return
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end subroutine gf64_encode
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