From 68f82c95de615c861c53dbe6b7b3bd5c031a1b68 Mon Sep 17 00:00:00 2001
From: Steve Franke <s.j.franke@icloud.com>
Date: Sat, 30 Mar 2019 15:55:05 -0500
Subject: [PATCH] FT4: Only do the big FFT once for each candidate. Duh.

---
 lib/ft4/ft4_decode.f90     |  8 +++++---
 lib/ft4/ft4_downsample.f90 | 16 +++++++++-------
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/lib/ft4/ft4_decode.f90 b/lib/ft4/ft4_decode.f90
index bd28b8899..83287e1e9 100644
--- a/lib/ft4/ft4_decode.f90
+++ b/lib/ft4/ft4_decode.f90
@@ -46,7 +46,7 @@ subroutine ft4_decode(cdatetime0,tbuf,nfa,nfb,nQSOProgress,ncontest,nfqso, &
 
    logical nohiscall,unpk77_success
    logical one(0:255,0:7)    ! 256 4-symbol sequences, 8 bits
-   logical first
+   logical first, dobigfft
 
    data icos4a/0,1,3,2/
    data icos4b/1,0,2,3/
@@ -189,12 +189,14 @@ subroutine ft4_decode(cdatetime0,tbuf,nfa,nfb,nQSOProgress,ncontest,nfqso, &
    call clockit('getcand4',1)
 
    ndecodes=0
+   dobigfft=.true.
    do icand=1,ncand
       f0=candidate(1,icand)
       snr=candidate(3,icand)-1.0
       if( f0.le.10.0 .or. f0.ge.4990.0 ) cycle
       call clockit('ft4_down',0)
-      call ft4_downsample(iwave,f0,cd2)  !Downsample from 512 to 32 Sa/Symbol
+      call ft4_downsample(iwave,dobigfft,f0,cd2)  !Downsample from 512 to 32 Sa/Symbol
+      if(dobigfft) dobigfft=.false.
       call clockit('ft4_down',1)
 
       sum2=sum(cd2*conjg(cd2))/(real(NMAX)/real(NDOWN))
@@ -238,7 +240,7 @@ subroutine ft4_decode(cdatetime0,tbuf,nfa,nfb,nQSOProgress,ncontest,nfqso, &
       if( f0.le.10.0 .or. f0.ge.4990.0 ) cycle
 
       call clockit('ft4down ',0)
-      call ft4_downsample(iwave,f0,cb) !Final downsample with corrected f0
+      call ft4_downsample(iwave,dobigfft,f0,cb) !Final downsample with corrected f0
       call clockit('ft4down ',1)
       sum2=sum(abs(cb)**2)/(real(NSS)*NN)
       if(sum2.gt.0.0) cb=cb/sqrt(sum2)
diff --git a/lib/ft4/ft4_downsample.f90 b/lib/ft4/ft4_downsample.f90
index ca5991346..8fb7c5d1d 100644
--- a/lib/ft4/ft4_downsample.f90
+++ b/lib/ft4/ft4_downsample.f90
@@ -1,4 +1,4 @@
-subroutine ft4_downsample(iwave,f0,c)
+subroutine ft4_downsample(iwave,newdata,f0,c)
 
 ! Input: i*2 data in iwave() at sample rate 12000 Hz
 ! Output: Complex data in c(), sampled at 1200 Hz
@@ -11,9 +11,9 @@ subroutine ft4_downsample(iwave,f0,c)
    complex cx(0:NMAX/2)
    real x(NMAX), window(0:NFFT2-1)
    equivalence (x,cx)
-   logical first
+   logical first, newdata
    data first/.true./
-   save first,window
+   save first,window,x
 
    df=12000.0/NMAX
    baud=12000.0/NSPS
@@ -32,14 +32,16 @@ subroutine ft4_downsample(iwave,f0,c)
       first=.false.
    endif
 
-   x=iwave
-   call four2a(x,NMAX,1,-1,0)             !r2c FFT to freq domain
+   if(newdata) then
+      x=iwave
+      call four2a(x,NMAX,1,-1,0)             !r2c FFT to freq domain
+   endif
    i0=nint(f0/df)
    c1=0.
    c1(0)=cx(i0)
    do i=1,NFFT2/2
-      if(i0+i.le.NMAX/2) c1(i)=cx(i0+i)
-      if(i0-i.ge.0) c1(NFFT2-i)=cx(i0-i)
+   if(i0+i.le.NMAX/2) c1(i)=cx(i0+i)
+   if(i0-i.ge.0) c1(NFFT2-i)=cx(i0-i)
    enddo
    c1=c1*window/NFFT2
    call four2a(c1,NFFT2,1,1,1)            !c2c FFT back to time domain