GPU TPC: Better formula for cluster weights

Author: davidrohr

GPU/GPUTracking/SectorTracker/GPUTPCTracker.h

@@ -160,13 +160,8 @@ class GPUTPCTracker : public GPUProcessor
    */
   GPUdi() static int32_t CalculateHitWeight(int32_t NHits, float chi2)
   {
-    const float chi2_suppress = 6.f;
-    float weight = (((float)NHits * (chi2_suppress - chi2 / 500.f)) * (1e9f / chi2_suppress / 160.f));
-    if (weight < 0.f || weight > 2e9f) {
-      return 0;
-    }
+    float weight = NHits * (NHits * 2 - 5) / chi2;
     return ((int32_t)weight);
-    // return( (NHits << 16) + num);
   }
   GPUd() void MaximizeHitWeight(const GPUTPCRow& row, int32_t hitIndex, int32_t weight) { mData.MaximizeHitWeight(row, hitIndex, weight); }
   GPUd() void SetHitWeight(const GPUTPCRow& row, int32_t hitIndex, int32_t weight) { mData.SetHitWeight(row, hitIndex, weight); }