From 323f20865dbb827c1c2137dbd55cf483eeef0fcc Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@fb.com>
Date: Tue, 8 Mar 2016 09:58:13 -0700
Subject: [PATCH 1/1] Add t/gen-rand to test random generator

Signed-off-by: Jens Axboe <axboe@fb.com>
---
 Makefile     |  9 +++++++
 t/gen-rand.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 77 insertions(+)
 create mode 100644 t/gen-rand.c

diff --git a/Makefile b/Makefile
index 684b565d..6b4c9dbf 100644
--- a/Makefile
+++ b/Makefile
@@ -211,6 +211,10 @@ T_LFSR_TEST_OBJS = t/lfsr-test.o
 T_LFSR_TEST_OBJS += lib/lfsr.o gettime.o t/log.o t/debug.o
 T_LFSR_TEST_PROGS = t/lfsr-test
 
+T_GEN_RAND_OBJS = t/gen-rand.o
+T_GEN_RAND_OBJS += t/log.o t/debug.o lib/rand.o lib/pattern.o lib/strntol.o
+T_GEN_RAND_PROGS = t/gen-rand
+
 ifeq ($(CONFIG_TARGET_OS), Linux)
 T_BTRACE_FIO_OBJS = t/btrace2fio.o
 T_BTRACE_FIO_OBJS += fifo.o lib/flist_sort.o t/log.o oslib/linux-dev-lookup.o
@@ -231,6 +235,7 @@ T_OBJS += $(T_IEEE_OBJS)
 T_OBJS += $(T_ZIPF_OBJS)
 T_OBJS += $(T_AXMAP_OBJS)
 T_OBJS += $(T_LFSR_TEST_OBJS)
+T_OBJS += $(T_GEN_RAND_OBJS)
 T_OBJS += $(T_BTRACE_FIO_OBJS)
 T_OBJS += $(T_DEDUPE_OBJS)
 T_OBJS += $(T_VS_OBJS)
@@ -246,6 +251,7 @@ T_TEST_PROGS += $(T_IEEE_PROGS)
 T_PROGS += $(T_ZIPF_PROGS)
 T_TEST_PROGS += $(T_AXMAP_PROGS)
 T_TEST_PROGS += $(T_LFSR_TEST_PROGS)
+T_TEST_PROGS += $(T_GEN_RAND_PROGS)
 T_PROGS += $(T_BTRACE_FIO_PROGS)
 T_PROGS += $(T_DEDUPE_PROGS)
 T_PROGS += $(T_VS_PROGS)
@@ -386,6 +392,9 @@ t/axmap: $(T_AXMAP_OBJS)
 t/lfsr-test: $(T_LFSR_TEST_OBJS)
 	$(QUIET_LINK)$(CC) $(LDFLAGS) $(CFLAGS) -o $@ $(T_LFSR_TEST_OBJS) $(LIBS)
 
+t/gen-rand: $(T_GEN_RAND_OBJS)
+	$(QUIET_LINK)$(CC) $(LDFLAGS) $(CFLAGS) -o $@ $(T_GEN_RAND_OBJS) $(LIBS)
+
 ifeq ($(CONFIG_TARGET_OS), Linux)
 t/fio-btrace2fio: $(T_BTRACE_FIO_OBJS)
 	$(QUIET_LINK)$(CC) $(LDFLAGS) $(CFLAGS) -o $@ $(T_BTRACE_FIO_OBJS) $(LIBS)
diff --git a/t/gen-rand.c b/t/gen-rand.c
new file mode 100644
index 00000000..c2a31bc1
--- /dev/null
+++ b/t/gen-rand.c
@@ -0,0 +1,68 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <inttypes.h>
+#include <assert.h>
+#include <math.h>
+#include <string.h>
+
+#include "../lib/types.h"
+#include "../log.h"
+#include "../lib/lfsr.h"
+#include "../lib/axmap.h"
+#include "../smalloc.h"
+#include "../minmax.h"
+#include "../lib/rand.h"
+
+int main(int argc, char *argv[])
+{
+	struct frand_state s;
+	uint64_t i, start, end, nvalues;
+	unsigned long *buckets, index, pass, fail;
+	double p, dev, mean, vmin, vmax;
+
+	if (argc < 4) {
+		log_err("%s: start end nvalues\n", argv[0]);
+		return 1;
+	}
+
+	start = strtoul(argv[1], NULL, 10);
+	end = strtoul(argv[2], NULL, 10);
+
+	if (start >= end) {
+		log_err("%s: start must be smaller than end\n", argv[0]);
+		return 1;
+	}
+	index = 1 + end - start;
+	buckets = calloc(index, sizeof(unsigned long));
+
+	nvalues = strtoul(argv[3], NULL, 10);
+
+	init_rand(&s, true);
+
+	for (i = 0; i < nvalues; i++) {
+		int v = rand_between(&s, start, end);
+
+		buckets[v - start]++;
+	}
+
+	p = 1.0 / index;
+	dev = sqrt(nvalues * p * (1.0 - p));
+	mean = nvalues * p;
+	vmin = mean - dev;
+	vmax = mean + dev;
+
+	pass = fail = 0;
+	for (i = 0; i < index; i++) {
+		if (buckets[i] < vmin || buckets[i] > vmax) {
+			printf("FAIL bucket%4lu: val=%8lu (%.1f < %.1f > %.1f)\n", i + 1, buckets[i], vmin, mean, vmax);
+			fail++;
+		} else {
+			printf("PASS bucket%4lu: val=%8lu (%.1f < %.1f > %.1f)\n", i + 1, buckets[i], vmin, mean, vmax);
+			pass++;
+		}
+	}
+
+	printf("Passes=%lu, Fail=%lu\n", pass, fail);
+
+	return 0;
+}
-- 
2.25.1