Estimate an upper bound on the number of particles to read into the cache and...

Estimate an upper bound on the number of particles to read into the cache and how many particles to loop over in DOPAIR2_VEC.

src/runner_doiact_vec.c

@@ -470,6 +470,27 @@ __attribute__((always_inline)) INLINE static void populate_max_index_no_cache_fo
     max_index_j[0] = ci->count - 1;
   }
 
+  int first_pi_est = first_pi;
+  int max_index_i_last = max_index_i[ci->count - 1];
+
+  if(max_index_j[0] < first_pi) {
+    first_pi = max_index_j[0];
+
+    for(int i=first_pi; i<ci->count; i++) {
+      max_index_i[i] = last_pj;
+    }
+
+  }
+  
+  if(max_index_i_last > last_pj) {
+    last_pj = max_index_i_last;
+
+    for(int i=0; i<=last_pj; i++) {
+      max_index_j[i] = first_pi_est;
+    }
+
+  }
+
   for(int i=0; i<ci->count; i++) max_index_i[i] = cj->count - 1;
   for(int i=0; i<cj->count; i++) max_index_j[i] = 0;
 
@@ -748,7 +769,6 @@ __attribute__((always_inline)) INLINE void runner_doself2_force_vec(
     if (pi->ti_drift != e->ti_current)
       error("Particle pi not drifted to current time");
   }
-}
 #endif
 
 /* Loop over the particles in the cell. */
@@ -1442,21 +1462,21 @@ void runner_dopair2_force_vec(struct runner *r, struct cell *ci,
                               hj_max, di_max, dj_min, max_index_i, max_index_j,
                               &first_pi, &last_pj, e);
 
-  /* Find the maximum index into cj that is required by a particle in ci. */
-  /* Find the maximum index into ci that is required by a particle in cj. */
-  int max_ind_j = max_index_i[count_j - 1];
-  int max_ind_i = max_index_j[0];
-
+  first_pi = 0;
+  last_pj = count_j - 1;
+  
   /* Limits of the outer loops. */
   int first_pi_loop = first_pi;
   int last_pj_loop = last_pj;
 
   /* Take the max/min of both values calculated to work out how many particles
    * to read into the cache. */
-  last_pj = max(last_pj, max_ind_j);
-  first_pi = min(first_pi, max_ind_i);
-
+  last_pj = max(last_pj, max_index_i[count_i - 1]);
+  first_pi = min(first_pi, max_index_j[0]);
   
+  first_pi = 0;
+  last_pj = count_j - 1;
+
   /* Read the needed particles into the two caches. */
   int first_pi_align = first_pi;
   int last_pj_align = last_pj;