a

1 files changed, 58 insertions, 0 deletions

diff --git a/tests/bench/sieve.c b/tests/bench/sieve.c
new file mode 100644
index 0000000..6ac503e
--- /dev/null
+++ b/tests/bench/sieve.c
@@ -0,0 +1,58 @@
+/* primes below N. the same loops as tests/bench/sieve.zc.
+   word: one int64 flag per number (what zc's fast path can do).
+   byte: one byte per number, the representation a C sieve would actually use.
+   the count is 9592 either way.
+   usage: sieve word|byte REPS */
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+enum { N = 100000, EXPECT = 9592 };
+
+static int sieve_word(int64_t *restrict f)
+{
+	int c = 0;
+	for (int i = 2; i < N; i++) f[i] = 1;
+	for (int i = 2; (long long)i * i < N; i++)
+		if (f[i])
+			for (int j = i * i; j < N; j += i) f[j] = 0;
+	for (int i = 2; i < N; i++) c += (int)f[i];
+	return c;
+}
+
+static int sieve_byte(unsigned char *restrict f)
+{
+	int c = 0;
+	for (int i = 2; i < N; i++) f[i] = 1;
+	for (int i = 2; (long long)i * i < N; i++)
+		if (f[i])
+			for (int j = i * i; j < N; j += i) f[j] = 0;
+	for (int i = 2; i < N; i++) c += f[i];
+	return c;
+}
+
+int main(int argc, char **argv)
+{
+	int reps, r = 0, k, byte;
+	int64_t *w = 0;
+	unsigned char *b = 0;
+	if (argc != 3) return 2;
+	byte = argv[1][0] == 'b';
+	reps = atoi(argv[2]);
+	if (byte) b = malloc(N);
+	else w = malloc((size_t)N * sizeof *w);
+	if (!w && !b) return 3;
+	for (k = 0; k < reps; k++) {
+		r = byte ? sieve_byte(b) : sieve_word(w);
+		/* the stores have to happen: the next pass must see a clobbered buffer */
+		__asm__ __volatile__("" : "+r"(r) : "r"(byte ? (void *)b : (void *)w) : "memory");
+	}
+	if (r != EXPECT) {
+		fprintf(stderr, "bad %d\n", r);
+		return 1;
+	}
+	printf("%d\n", r);
+	free(w);
+	free(b);
+	return 0;
+}