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-rw-r--r--set_bitsets.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/set_bitsets.c b/set_bitsets.c
index f59e61e..4ac8462 100644
--- a/set_bitsets.c
+++ b/set_bitsets.c
@@ -24,13 +24,13 @@ int nb_one(unsigned long long x) { //the hamming weight of x
assert(SCOD==64);
//1
- x = (x & 0x5555555555555555) + ((x >> 1) & 0x5555555555555555);
+ x = (x & 0x5555555555555555) + ((x >> 1) & 0x5555555555555555); // mask : 0101010101...
//2
- x = (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333);
+ x = (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333); // mask : 001100110011...
//4
- x = (x & 0x0F0F0F0F0F0F0F0F) + ((x >> 4) & 0x0F0F0F0F0F0F0F0F);
+ x = (x & 0x0F0F0F0F0F0F0F0F) + ((x >> 4) & 0x0F0F0F0F0F0F0F0F); // mask : 000011110000....
//8
- x = (x & 0x00FF00FF00FF00FF) + ((x >> 8) & 0x00FF00FF00FF00FF);
+ x = (x & 0x00FF00FF00FF00FF) + ((x >> 8) & 0x00FF00FF00FF00FF); // etc.
//16
x = (x & 0x0000FFFF0000FFFF) + ((x >> 16) & 0x0000FFFF0000FFFF);
//32