From d82b9f5b0e10e9cef76e3d823cf5b9f1244e52a0 Mon Sep 17 00:00:00 2001
From: Steven Franke <s.j.franke@icloud.com>
Date: Mon, 24 Aug 2020 10:17:45 -0500
Subject: [PATCH] Speed up decoder by eliminating some complex multiples in
 sequence detection loop. Add timer calls for doppler spread calculation and
 sequence detection loop.

---
 lib/fst4/get_fst4_bitmetrics.f90 | 13 ++++++++++---
 lib/fst4_decode.f90              |  2 ++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/lib/fst4/get_fst4_bitmetrics.f90 b/lib/fst4/get_fst4_bitmetrics.f90
index e245db18c..69a649a04 100644
--- a/lib/fst4/get_fst4_bitmetrics.f90
+++ b/lib/fst4/get_fst4_bitmetrics.f90
@@ -1,5 +1,6 @@
 subroutine get_fst4_bitmetrics(cd,nss,hmod,nmax,nhicoh,bitmetrics,s4,nsync_qual,badsync)
 
+   use timer_module, only: timer
    include 'fst4_params.f90'
    complex cd(0:NN*nss-1)
    complex cs(0:3,NN)
@@ -84,6 +85,8 @@ subroutine get_fst4_bitmetrics(cd,nss,hmod,nmax,nhicoh,bitmetrics,s4,nsync_qual,
       return
    endif
 
+
+   call timer('seqcorrs',0)
    bitmetrics=0.0
    do nseq=1,nmax            !Try coherent sequences of 1,2,3,4 or 1,2,4,8 symbols
       if(nseq.eq.1) nsym=1
@@ -100,11 +103,14 @@ subroutine get_fst4_bitmetrics(cd,nss,hmod,nmax,nhicoh,bitmetrics,s4,nsync_qual,
          s2=0
          do i=0,nt-1
             csum=0
-            cterm=1
+!            cterm=1  ! hmod.ne.1
+            term=1
             do j=0,nsym-1
                ntone=mod(i/4**(nsym-1-j),4)
-               csum=csum+cs(graymap(ntone),ks+j)*cterm
-               cterm=cterm*conjg(cp(graymap(ntone)))
+               csum=csum+cs(graymap(ntone),ks+j)*term 
+               term=-term
+!               csum=csum+cs(graymap(ntone),ks+j)*cterm  ! hmod.ne.1
+!               cterm=cterm*conjg(cp(graymap(ntone)))    ! hmod.ne.1
             enddo
             s2(i)=abs(csum)
          enddo
@@ -122,6 +128,7 @@ subroutine get_fst4_bitmetrics(cd,nss,hmod,nmax,nhicoh,bitmetrics,s4,nsync_qual,
          enddo
       enddo
    enddo
+   call timer('seqcorrs',1)
 
    hbits=0
    where(bitmetrics(:,1).ge.0) hbits=1
diff --git a/lib/fst4_decode.f90 b/lib/fst4_decode.f90
index 444553618..efe6a3798 100644
--- a/lib/fst4_decode.f90
+++ b/lib/fst4_decode.f90
@@ -455,10 +455,12 @@ contains
                      endif
                      inquire(file='plotspec',exist=ex)
                      fmid=-999.0
+                     call timer('dopsprd ',0)
                      if(ex) then
                         call dopspread(itone,iwave,nsps,nmax,ndown,hmod,  &
                            isbest,fc_synced,fmid,w50)
                      endif
+                     call timer('dopsprd ',1)
                      xsig=0
                      do i=1,NN
                         xsig=xsig+s4(itone(i),i)