Minor tweak to effectcrep

Slightly more efficient parity implementation (fewer operations), and add the compiler hint to inline the parity function. In profiling this makes a surprisingly big difference.

pygsti/evotypes/densitymx/effectcreps.cpp

@@ -147,7 +147,7 @@ namespace CReps_densitymx {
 	finalIndx += ((finds >> k) & 1) * 3 * base;
 	base = base >> 2; // /= 4 so base == 4**(N-1-k)
       }
-
+      
       //Apply result
       if(parity(finds & _zvals_int))
 	ret -= _abs_elval * state->_dataptr[finalIndx]; // minus sign
@@ -157,15 +157,25 @@ namespace CReps_densitymx {
     return ret;
   }
 
-  INT EffectCRep_Computational::parity(INT x) {
-    // int64-bit specific
-    x = (x & 0x00000000FFFFFFFF)^(x >> 32);
-    x = (x & 0x000000000000FFFF)^(x >> 16);
-    x = (x & 0x00000000000000FF)^(x >> 8);
-    x = (x & 0x000000000000000F)^(x >> 4);
-    x = (x & 0x0000000000000003)^(x >> 2);
-    x = (x & 0x0000000000000001)^(x >> 1);
-    return x & 1; // return the last bit (0 or 1)
+//  INT EffectCRep_Computational::parity(INT x) {
+//    // int64-bit specific
+//    x = (x & 0x00000000FFFFFFFF)^(x >> 32);
+//    x = (x & 0x000000000000FFFF)^(x >> 16);
+//    x = (x & 0x00000000000000FF)^(x >> 8);
+//    x = (x & 0x000000000000000F)^(x >> 4);
+//    x = (x & 0x0000000000000003)^(x >> 2);
+//    x = (x & 0x0000000000000001)^(x >> 1);
+//    return x & 1; // return the last bit (0 or 1)
+//  }
+
+  inline INT EffectCRep_Computational::parity(INT x) {
+    x ^= (x >> 32);
+    x ^= (x >> 16);
+    x ^= (x >> 8);
+    x ^= (x >> 4);
+    x ^= (x >> 2);
+    x ^= (x >> 1);
+    return x & 1; // Return the last bit
   }