Improving reduced step by passing 3 indices including the absolute last

index (not "-1")

src/main/java/com/elphel/imagej/tileprocessor/OpticalFlow.java

@@ -4781,7 +4781,7 @@ public class OpticalFlow {
 			boolean                                              reset_from_extrinsics,
 			String [][]                                          videos, // null or String[1][] list of generated avi or webm paths
 			int [][]                                             stereo_widths, // null or int[1][] matching videos -
-			int []                                               start_ref_pointers, // [0] - earliest valid scene, [1] ref_index
+			int []                                               start_ref_pointers, // [0] - earliest valid scene, [1] ref_index 01/21/2026 - added third element - last pointer, avoiding relative -1.
 			                                                     // each element is 0 for non-stereo and full width for stereo 
 			String []                                            cuas_centers, // [0] - cumulative input, [1] - cumulative output
 			// processing UAS logs
@@ -4978,6 +4978,7 @@ public class OpticalFlow {
 		if (start_ref_pointers != null) {
 			start_ref_pointers[0] = 0;
 			start_ref_pointers[1] = last_index;
+			start_ref_pointers[2] = last_index; // this will not be modified anymore - just to calculate smaller overlap by the caller
 		}
 		
 		

src/main/java/com/elphel/imagej/tileprocessor/TwoQuadCLT.java

@@ -8567,7 +8567,7 @@ if (debugLevel > -100) return true; // temporarily !
 				String [][] video_list = new String[1][];
 				int [][] widths_list = new int [1][];
 				int ref_index = -1; // -1 - last
-				int [] start_ref_pointers = new int[2]; //{earlist, reference} - reference may be center
+				int [] start_ref_pointers = new int[3]; //{earlist, reference} - reference may be center
 				index_scenes[0] = null; // boolean     first_in_series = true; 
 				/*
 				// Process UAS logs 
@@ -8692,33 +8692,21 @@ if (debugLevel > -100) return true; // temporarily !
 					// testing half-step
 					if (start_ref_pointers[0] >= (min_num_scenes-1)) {
 						System.out.println("testing half-step: start_ref_pointers[0]="+start_ref_pointers[0]+
-								", start_ref_pointers[1]="+start_ref_pointers[1]+", ref_index="+ref_index);
+								", start_ref_pointers[1]="+start_ref_pointers[1]+", start_ref_pointers[2]="+start_ref_pointers[2]+", ref_index="+ref_index);
 						int offset1 = (int) (overlap_scale * (start_ref_pointers[1] - start_ref_pointers[0]));
 						int offset2 = (start_ref_pointers[1] - start_ref_pointers[0]) - offset1;
 						System.out.println("testing half-step:  offset1="+offset1+
 								",  offset2="+offset2+" overlap_scale="+overlap_scale);
-						start_ref_pointers[0] = start_ref_pointers[1]  - offset1;
+						start_ref_pointers[0] = Math.max ( start_ref_pointers[0] , start_ref_pointers[1]  - offset1);
 						// incorrect, fix  "-1" to actual last scene
-						start_ref_pointers[1] += offset2;  
+//						start_ref_pointers[1] += offset2;
+						start_ref_pointers[1] = Math.max (start_ref_pointers[2],  start_ref_pointers[1]  - offset1);
 						System.out.println("testing half-step: start_ref_pointers[0]="+start_ref_pointers[0]+
-								", start_ref_pointers[1]="+start_ref_pointers[1]+", ref_index="+ref_index);
+								", start_ref_pointers[1]="+start_ref_pointers[1]+", start_ref_pointers[2]="+start_ref_pointers[2]+", ref_index="+ref_index);
 					}
-					/*
-					if (start_ref_pointers[0] >= (min_num_scenes-1)) {
-						System.out.println("testing half-step: start_ref_pointers[0]="+start_ref_pointers[0]+
-								", start_ref_pointers[1]="+start_ref_pointers[1]+", ref_index="+ref_index);
-						int offset = (int) overlap_scale * (start_ref_pointers[1] - start_ref_pointers[0]);
-						start_ref_pointers[0] += offset;
-						start_ref_pointers[1] += offset;
-						System.out.println("testing half-step: start_ref_pointers[0]="+start_ref_pointers[0]+
-								", start_ref_pointers[1]="+start_ref_pointers[1]+", ref_index="+ref_index);
-					}
-					 */
-					
 					
 					String series_action = (start_ref_pointers[0] < (min_num_scenes-1))?"is FINISHED ":("will continue down from scene "+(start_ref_pointers[0]));
 
-
 					System.out.println("\n ----- PROCESSING SCENE SEQUENCE "+nseq+" (last is "+(num_seq-1)+") "+series_action+" in "+
 							IJ.d2s(0.000000001*(System.nanoTime()-start_time_seq),3)+" sec ("+
 							IJ.d2s(0.000000001*(System.nanoTime()-start_time_all),3)+" sec from the overall start\n");