math: Added parity check to ProbablyPrime

Fixes golang#9269 Change-Id: I25751632e95978537b656aedfa5c35ab2273089b Reviewed-on: https://go-review.googlesource.com/1380 Reviewed-by: Robert Griesemer <[email protected]>
bpd1069 · Dec 12, 2014 · 5de497b · 5de497b
1 parent da43976
commit 5de497b
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/src/math/big/nat.go b/src/math/big/nat.go
@@ -1404,6 +1404,10 @@ func (n nat) probablyPrime(reps int) bool {
 		}
 	}
 
+	if n[0]&1 == 0 {
+		return false // n is even
+	}
+
 	const primesProduct32 = 0xC0CFD797         // Π {p ∈ primes, 2 < p <= 29}
 	const primesProduct64 = 0xE221F97C30E94E1D // Π {p ∈ primes, 2 < p <= 53}