30/06/2011

Correct the bug to get COD and one turn map for the lattice with negative momentum compact factor.

tracy/tracy/src/t2cell.cc

@@ -792,11 +792,17 @@ bool Cell_GetCOD_M(long imax, double eps, double dP, long &lastpos)
    Comments:
        Called by getCOD, Ring_Pass
 
+       27/06/11   Correct the bug for the negative momentum compact factor; if the momentum
+                  compact is negative, then switch the Stable Fixed Point to Unstable Fixed Point.
+		  For Cell_GetCOD_M, the tracking is in 4D, so there is no switch of 
+     fixed point for the lattice with negative momentum compact factor.  
+      28/06/11   Correct the one turn map for the lattice with negative momentum compact factor, now the one turn map is
+      tracked around the COD.
 ****************************************************************************/
 bool Cell_getCOD(long imax, double eps, double dP, long &lastpos)
 {
-  long             j, n, n_iter;
-  double           dxabs;
+  long             j = 0, n = 0, n_iter = 0, h_RF = 0;
+  double           dxabs = 0.0;
   iVector          jj;
   ss_vect<double>  x0, x1, dx;
   ss_vect<tps>     I, dx0, map;
@@ -875,6 +881,20 @@ bool Cell_getCOD(long imax, double eps, double dP, long &lastpos)
       }
     } while ((dxabs >= eps) && (n_iter <= imax));
 
+  
+  //if momentum compact factor is negative, then swtich the fixed point(SFP->UFP)  
+  h_RF = Cell[Elem_GetPos(globval.cav, 1)].Elem.C->Ph;
+  if(globval.Alphac < 0) 
+     x0[ct_] =  -0.5*Cell[globval.Cell_nLoc].S/h_RF- x0[ct_]; //since the value of x0[ct_] is negative, so use "-0.5"
+  if(0)
+    cout<< " c*tau0 is: " << x0[ct_] <<endl;
+ 
+  //get the one turn map for the close orbit
+  map.identity(); 
+  map += x0;
+  Cell_Pass(0, globval.Cell_nLoc, map, lastpos); 
+  
+  
   status.codflag = dxabs < eps;
 
   if (status.codflag)