From ab3832fa822eda49f60cece52f6921e9c5f72138 Mon Sep 17 00:00:00 2001
From: Joe Taylor <k1jt@arrl.org>
Date: Mon, 3 Jul 2017 19:52:36 +0000
Subject: [PATCH] In ft8_downsample, compute long FFT only when data have
 changed.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7780 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
---
 lib/decoder.f90     |  5 +++--
 lib/fsk4hf/ft8b.f90 | 22 ++++++++++++++--------
 lib/ft8_decode.f90  |  2 +-
 lib/refspectrum.f90 |  2 --
 4 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/lib/decoder.f90 b/lib/decoder.f90
index 0d5153a2e..e1346b4c4 100644
--- a/lib/decoder.f90
+++ b/lib/decoder.f90
@@ -28,7 +28,7 @@ subroutine multimode_decoder(ss,id2,params,nfsample)
   end type counting_ft8_decoder
 
   real ss(184,NSMAX)
-  logical baddata,newdat65,newdat9,single_decode,bVHF,bad0
+  logical baddata,newdat65,newdat9,single_decode,bVHF,bad0,newdat
   integer*2 id2(NTMAX*12000)
   type(params_block) :: params
   real*4 dd(NTMAX*12000)
@@ -69,8 +69,9 @@ subroutine multimode_decoder(ss,id2,params,nfsample)
   if(params%nmode.eq.8) then
 ! We're in FT8 mode
      call timer('decft8  ',0)
+     newdat=params%newdat
      call my_ft8%decode(ft8_decoded,id2,params%nfqso,                   &
-          newdat9,params%nutc,params%nfa,      &
+          newdat,params%nutc,params%nfa,      &
           params%nfb,logical(params%nagain),     &
           params%ndepth,params%nsubmode)
      call timer('decft8  ',1)
diff --git a/lib/fsk4hf/ft8b.f90 b/lib/fsk4hf/ft8b.f90
index 8c26b0197..32557340a 100644
--- a/lib/fsk4hf/ft8b.f90
+++ b/lib/fsk4hf/ft8b.f90
@@ -1,4 +1,4 @@
-subroutine ft8b(dd0,nfqso,f1,xdt,nharderrors,dmin,nbadcrc,message,xsnr)
+subroutine ft8b(dd0,newdat,nfqso,f1,xdt,nharderrors,dmin,nbadcrc,message,xsnr)
 
   use timer_module, only: timer
   include 'ft8_params.f90'
@@ -17,7 +17,7 @@ subroutine ft8b(dd0,nfqso,f1,xdt,nharderrors,dmin,nbadcrc,message,xsnr)
   complex csync(0:6,32)
   complex ctwk(32)
   complex csymb(32)
-  logical first
+  logical newdat,first
   data icos7/2,5,6,0,4,1,3/
   data first/.true./
   save first,twopi,fs2,dt2,taus,baud,csync
@@ -43,7 +43,7 @@ subroutine ft8b(dd0,nfqso,f1,xdt,nharderrors,dmin,nbadcrc,message,xsnr)
   norder=2
 !  if(abs(nfqso-f1).lt.10.0) norder=3
   call timer('ft8_down',0)
-  call ft8_downsample(dd0,f1,cd0)
+  call ft8_downsample(dd0,newdat,f1,cd0)
   call timer('ft8_down',1)
 
   i0=xdt*fs2
@@ -189,22 +189,28 @@ subroutine ft8b(dd0,nfqso,f1,xdt,nharderrors,dmin,nbadcrc,message,xsnr)
   return
 end subroutine ft8b
 
-subroutine ft8_downsample(dd,f0,c1)
+subroutine ft8_downsample(dd,newdat,f0,c1)
 
 ! Downconvert to complex data sampled at 187.5 Hz, 32 samples/symbol
 
   parameter (NMAX=15*12000)
   parameter (NFFT1=200000,NFFT2=3125)      !200000/64 = 3125
+  logical newdat
   complex c1(0:NFFT2-1)
   complex cx(0:NFFT1/2)
   real dd(NMAX),x(NFFT1)
   equivalence (x,cx)
-  save x
+  save cx
+
+  if(newdat) then
+! Data in dd have changed, recompute the long FFT     
+     x(1:NMAX)=dd
+     x(NMAX+1:NFFT1)=0.                       !Zero-pad the x array
+     call four2a(cx,NFFT1,1,-1,0)             !r2c FFT to freq domain
+     newdat=.false.
+  endif
 
   df=12000.0/NFFT1
-  x(1:NMAX)=dd
-  x(NMAX+1:NFFT1)=0.                       !Zero-pad the x array
-  call four2a(cx,NFFT1,1,-1,0)             !r2c FFT to freq domain
   baud=12000.0/2048.0
   i0=nint(f0/df)
   ft=f0+8.0*baud
diff --git a/lib/ft8_decode.f90 b/lib/ft8_decode.f90
index 5905385c4..f7dc7cf48 100644
--- a/lib/ft8_decode.f90
+++ b/lib/ft8_decode.f90
@@ -56,7 +56,7 @@ contains
        xdt=candidate(2,icand)
        nsnr=min(99,nint(10.0*log10(sync) - 25.5))    !### empirical ###
        call timer('ft8b    ',0)
-       call ft8b(dd,nfqso,f1,xdt,nharderrors,dmin,nbadcrc,message,xsnr)
+       call ft8b(dd,newdat,nfqso,f1,xdt,nharderrors,dmin,nbadcrc,message,xsnr)
        nsnr=xsnr       
        xdt=xdt-0.6
        call timer('ft8b    ',1)
diff --git a/lib/refspectrum.f90 b/lib/refspectrum.f90
index 982813b98..8d0730df9 100644
--- a/lib/refspectrum.f90
+++ b/lib/refspectrum.f90
@@ -25,8 +25,6 @@ subroutine refspectrum(id2,id2b,kk,bclear,brefspec,buseref,fname)
   data first/.true./,blastuse/.false./
   save
 
-  print*,fname
-
   if(first) then
      pi=4.0*atan(1.0)
      do i=0,NFFT-1