Changeset 674 for codes/icosagcm/devel/Python/src/partition.c

Timestamp:

01/31/18 15:14:35 (6 years ago)

Author:

dubos

Message:

devel/unstructured : mesh reordering (Morton)

File:

• codes/icosagcm/devel/Python/src/partition.c (modified) (1 diff)

codes/icosagcm/devel/Python/src/partition.c

@@ -29 +29 @@
                        tpwgts, ubvec, options, &edgecut, part, &comm); 
 }
+
+
+// http://www.forceflow.be/2013/10/07/morton-encodingdecoding-through-bit-interleaving-implementations/ 
+// method to seperate bits from a given integer 3 positions apart
+static inline uint64_t splitBy3(unsigned int a){
+  uint64_t x = a & 0x1fffff; // we only look at the first 21 bits
+  x = (x | x << 32) & 0x1f00000000ffff;  // shift left 32 bits, OR with self, and 00011111000000000000000000000000000000001111111111111111
+  x = (x | x << 16) & 0x1f0000ff0000ff;  // shift left 32 bits, OR with self, and 00011111000000000000000011111111000000000000000011111111
+  x = (x | x << 8) & 0x100f00f00f00f00f; // shift left 32 bits, OR with self, and 0001000000001111000000001111000000001111000000001111000000000000
+  x = (x | x << 4) & 0x10c30c30c30c30c3; // shift left 32 bits, OR with self, and 0001000011000011000011000011000011000011000011000011000100000000
+  x = (x | x << 2) & 0x1249249249249249;
+  return x;
+}
+ 
+static inline uint64_t mortonEncode_magicbits(unsigned int x, unsigned int y, unsigned int z){
+  uint64_t answer = 0;
+  answer |= splitBy3(x) | splitBy3(y) << 1 | splitBy3(z) << 2;
+  return answer;
+}
+
+void dynamico_morton_encode(int n, const int *x, const int *y, const int *z, uint64_t *m)
+{
+  for(int i=0; i<n; i++)
+    m[i]=mortonEncode_magicbits(x[i],y[i],z[i]);
+}