Experimental work-around for FT8 decoding on slow computers. Important changes:

- don't start function decode() is decoder is already busy
  - send updated m_ihsym to jt9[.exe] via ss(1,1).  Bill won't like this!
  - jt9 bails out of the 41-buffer pass at m_ihsym=45.

lib/decoder.f90

@@ -108,7 +108,7 @@ subroutine multimode_decoder(ss,id2,params,nfsample)
           params%nftx,newdat,params%nutc,params%nfa,params%nfb,              &
           params%nzhsym,params%ndepth,ncontest,logical(params%nagain),       &
           logical(params%lft8apon),logical(params%lapcqonly),                &
-          params%napwid,mycall,hiscall,hisgrid)
+          params%napwid,mycall,hiscall,hisgrid,ss(1,1))
      call timer('decft8  ',1)
      if(nfox.gt.0) then
         n30min=minval(n30fox(1:nfox))

lib/ft8_decode.f90

@@ -34,7 +34,7 @@ contains
 
   subroutine decode(this,callback,iwave,nQSOProgress,nfqso,nftx,newdat,  &
        nutc,nfa,nfb,nzhsym,ndepth,ncontest,nagain,lft8apon,lapcqonly,    &
-       napwid,mycall12,hiscall12,hisgrid6)
+       napwid,mycall12,hiscall12,hisgrid6,ss0)
     use timer_module, only: timer
     include 'ft8/ft8_params.f90'
 
@@ -61,6 +61,7 @@ contains
     real xdt_save(MAX_EARLY)
 
     save s,dd,dd1,ndec_early,itone_save,f1_save,xdt_save,lsubtracted
+    volatile ss0
 
     this%callback => callback
     write(datetime,1001) nutc        !### TEMPORARY ###
@@ -171,11 +172,11 @@ contains
               call this%callback(sync,nsnr,xdt,f1,msg37,iaptype,qual)
            endif
         endif
+        if(nint(ss0).eq.45) go to 800         !Bail out before finishing
       enddo
    enddo
-   ndec_early=0
+800 ndec_early=0
    if(nzhsym.lt.50) ndec_early=ndecodes
-!   print*,'BBB',nzhsym,ndecodes
    
 900 return
 end subroutine decode

lib/jt9a.f90

@@ -23,6 +23,7 @@ subroutine jt9a()
   type(dec_data), pointer :: shared_data
   type(params_block) :: local_params
   logical fileExists
+  volatile shared_data
 
 ! Multiple instances:
   i0 = len(trim(shm_key))
@@ -78,6 +79,7 @@ subroutine jt9a()
   endif
 ! Normal decoding pass
   call multimode_decoder(shared_data%ss,shared_data%id2,local_params,12000)
+!  print*,'AAA',shared_data%ss(1,1)
   call timer('decoder ',1)
 
 100 inquire(file=trim(temp_dir)//'/.lock',exist=fileExists)

widgets/mainwindow.cpp

@@ -1411,6 +1411,10 @@ void MainWindow::dataSink(qint64 frames)
     m_dialFreqRxWSPR=m_freqNominal;
   }
 
+  if(m_mode=="FT8") {
+    to_jt9(m_ihsym); //Allow jt9 to bail out early, if necessary
+  }
+
   if(m_ihsym==m_hsymStop or (m_mode=="FT8" and m_ihsym==m_earlyDecode and !m_diskData) or
      (m_mode=="FT8" and m_ihsym==m_earlyDecode2 and !m_diskData)) {
     if(m_mode=="Echo") {
@@ -2079,7 +2083,12 @@ void MainWindow::keyPressEvent (QKeyEvent * e)
         return;
       }
       break;
-    case Qt::Key_PageUp:
+    case Qt::Key_Z:                            //### Recover from hung decode() ?? ###
+      if(e->modifiers() & Qt::AltModifier) {
+        decodeDone();
+        return;
+      }
+    break;    case Qt::Key_PageUp:
 
       break;
     case Qt::Key_PageDown:
@@ -2816,6 +2825,7 @@ void MainWindow::msgAvgDecode2()
 
 void MainWindow::decode()                                       //decode()
 {
+  if(m_decoderBusy) return;                          //Don't start decoder if it's already busy.
   QDateTime now = QDateTime::currentDateTimeUtc ();
   if( m_dateTimeLastTX.isValid () ) {
     qint64 isecs_since_tx = m_dateTimeLastTX.secsTo(now);
@@ -2987,8 +2997,15 @@ void MainWindow::decode()                                       //decode()
         dec_data.params.mycall,dec_data.params.hiscall,8000,12,12)));
   } else {
     memcpy(to, from, qMin(mem_jt9->size(), size));
+    if(m_mode=="FT8") to_jt9(m_ihsym);                     //### TEMPORARY ? ###
     QFile {m_config.temp_dir ().absoluteFilePath (".lock")}.remove (); // Allow jt9 to start
-//    qDebug() << "aa" << QDateTime::currentDateTimeUtc().toString("hh:mm:ss.s") << m_ihsym;
+
+    auto now = QDateTime::currentDateTimeUtc();
+    double tseq = fmod(double(now.toMSecsSinceEpoch() ),1000.0*m_TRperiod)/1000.0;
+    if(tseq < 0.5*m_TRperiod) tseq+= m_TRperiod;
+    if(m_ihsym==41) qDebug() << "";
+    qDebug() << "aa" << QDateTime::currentDateTimeUtc().toString("hh:mm:ss.zzz")
+             << tseq << m_ihsym << m_ndepth << from_jt9();
     decodeBusy(true);
   }
 }
@@ -3018,7 +3035,6 @@ void::MainWindow::fast_decode_done()
       m_bDecoded=true;
     }
     postDecode (true, decodedtext.string ());
-//    writeAllTxt(message);
     write_all("Rx",message);
 
     if(m_mode=="JT9" or m_mode=="MSK144") {
@@ -3037,6 +3053,19 @@ void::MainWindow::fast_decode_done()
   m_bFastDone=false;
 }
 
+void MainWindow::to_jt9(qint32 n)
+{
+  float ss0=n;
+  memcpy((char*)mem_jt9->data(),&ss0,4);
+//  qDebug() << "cc" << ss0 << "sent to jt9";
+}
+qint32 MainWindow::from_jt9()
+{
+  float ss0;
+  memcpy(&ss0,(char*)mem_jt9->data(),4);
+  return int(ss0);
+}
+
 void MainWindow::decodeDone ()
 {
   dec_data.params.nagain=0;
@@ -3050,7 +3079,12 @@ void MainWindow::decodeDone ()
   if(m_mode=="FT8" and dec_data.params.nzhsym==m_earlyDecode) m_blankLine=false;
   if(m_mode=="FT8" and dec_data.params.nzhsym==m_earlyDecode2) m_blankLine=false;
   if(SpecOp::FOX == m_config.special_op_id()) houndCallers();
-//  qDebug() << "cc" << QDateTime::currentDateTimeUtc().toString("hh:mm:ss.zzz");
+
+  auto now = QDateTime::currentDateTimeUtc();
+  double tseq = fmod(double(now.toMSecsSinceEpoch() ),1000.0*m_TRperiod)/1000.0;
+  if(tseq < 0.5*m_TRperiod) tseq+= m_TRperiod;
+  qDebug() << "bb" << QDateTime::currentDateTimeUtc().toString("hh:mm:ss.zzz")
+           << tseq << m_ihsym << from_jt9();
 }
 
 void MainWindow::readFromStdout()                             //readFromStdout

widgets/mainwindow.h

@@ -759,8 +759,7 @@ private:
   qint64  nWidgets(QString t);
   void displayWidgets(qint64 n);
   void vhfWarning();
-  QChar current_submode () const; // returns QChar {0} if sub mode is
-                                  // not appropriate
+  QChar current_submode () const; // returns QChar {0} if submode is not appropriate
   void write_transmit_entry (QString const& file_name);
   void selectHound(QString t);
   void houndCallers();
@@ -768,6 +767,8 @@ private:
   void foxTxSequencer();
   void foxGenWaveform(int i,QString fm);
   void writeFoxQSO (QString const& msg);
+  void to_jt9(qint32 n);
+  qint32 from_jt9();
 };
 
 extern int killbyname(const char* progName);