For PH, all-odd keys in the vector are not necessary.

src/ph.c

@@ -207,14 +207,8 @@ PH_Generate(char * const * const strings, unsigned n)
 	h1->minlen = min;
 	h1->maxlen = max;
 	h1->l = l;
-	/*
-	 * XXX the literature sometimes says that the keys should all be
-	 * odd, since repeated multiplication makes the result tend to 0,
-	 * but sometimes doesn't mention it. Not sure if |1 is needed
-	 * here.
-	 */
 	for (unsigned i = 0; i < l; i++)
-		h1->k[i] = rnd64() | 1;
+		h1->k[i] = rnd64();
 	h1->mask = sz - 1;
 
 	for (unsigned i = 0; i < n; i++) {
@@ -283,9 +277,8 @@ PH_Generate(char * const * const strings, unsigned n)
 		if (bhsh->k == NULL)
 			goto exit;
 		bhsh->addend = rnd64();
-		/* XXX as above, unsure about |1 here */
 		for (unsigned j = 0; j < bhsh->l; j++)
-			bhsh->k[j] = rnd64() | 1;
+			bhsh->k[j] = rnd64();
 
 		for (int j = 0; j < bucket->n; j++) {
 			uint32_t h = hash(bhsh, strings[bucket->idx[j]],
@@ -297,7 +290,7 @@ PH_Generate(char * const * const strings, unsigned n)
 				       bsz * sizeof(*bhsh->tbl));
 				bhsh->addend = rnd64();
 				for (unsigned k = 0; k < bhsh->l; k++)
-					bhsh->k[k] = rnd64() | 1;
+					bhsh->k[k] = rnd64();
 				continue;
 			}
 			bhsh->tbl[h] = bucket->idx[j];