Add some sanity checks to getcandidates4.f90

lib/ft4/getcandidates4.f90

@@ -27,7 +27,7 @@ subroutine getcandidates4(id,fa,fb,syncmin,nfqso,maxcand,savg,candidate,   &
 ! Compute symbol spectra, stepping by NSTEP steps.  
   savg=0.
   tstep=NSTEP/12000.0                         
-  df=12000.0/NFFT1                            !5.86 Hz
+  df=12000.0/NFFT1                            
   fac=1.0/300.0
   do j=1,NHSYM
      ia=(j-1)*NSTEP + 1
@@ -55,17 +55,28 @@ subroutine getcandidates4(id,fa,fb,syncmin,nfqso,maxcand,savg,candidate,   &
   indx=0
   call indexx(savsm(n300:n2500),np,indx)
   xn=savsm(nfa+indx(nint(0.3*np)))
-  savsm=savsm/xn
-
   ncand=0
+  if(xn.le.1.e-8) return 
+  savsm=savsm/xn
+!  call ft4_baseline(savg,nfa,nfb,sbase)
+!  savsm=savsm/sbase
+
   f_offset = -1.5*12000/512
   do i=nfa+1,nfb-1
     if(savsm(i).ge.savsm(i-1) .and. savsm(i).ge.savsm(i+1) .and. savsm(i).ge.syncmin) then
-      del=0.5*(savsm(i-1)-savsm(i+1))/(savsm(i-1)-2*savsm(i)+savsm(i+1))
+      den=savsm(i-1)-2*savsm(i)+savsm(i+1)
+      if(den.ne.0.0) then
+         del=0.5*(savsm(i-1)-savsm(i+1))/den
+      else
+         del=0.0
+      endif
       fpeak=(i+del)*df+f_offset
       speak=savsm(i) - 0.25*(savsm(i-1)-savsm(i+1))*del
       ncand=ncand+1
-      if(ncand.gt.maxcand) exit
+      if(ncand.gt.maxcand) then
+         ncand=maxcand
+         exit
+      endif
       candidate(1,ncand)=fpeak
       candidate(2,ncand)=-99.99
       candidate(3,ncand)=speak