From 5fe3db54285ece5f385e819f594a648a9fb5c612 Mon Sep 17 00:00:00 2001
From: Richard Thier <magosit@outlook.hu>
Date: Tue, 1 Apr 2025 20:25:53 +0200
Subject: [PATCH] much better perf tests because no summing now that serialized
 opcodes

---
 makefile |  2 ++
 perf.cpp | 54 ++++++++++++++++++++++++++++++++++++------------------
 2 files changed, 38 insertions(+), 18 deletions(-)

diff --git a/makefile b/makefile
index b97102c..fb59045 100644
--- a/makefile
+++ b/makefile
@@ -4,3 +4,5 @@ release:
 	gcc main.c -O2 -o main
 perf:
 	g++ perf.cpp -O2 -o perftest; ./perftest
+perf-debug:
+	g++ perf.cpp -g -o perftest; gdb ./perftest
diff --git a/perf.cpp b/perf.cpp
index eedba51..bd23af0 100644
--- a/perf.cpp
+++ b/perf.cpp
@@ -5,82 +5,100 @@
 #include "fastrand.h"
 
 #define N 10000000
-#define M 99999999 // M > N
+// #define N 19999999
+// #define M 10000000 // M >= N
+#define M 19999999 // M >= N
 #define FROM 100
 #define TO 576
 
+uint32_t res[M] = { 0 };
+
 int main() {
-	assert(M > N); // M > N
+	assert(M >= N); // M >= N
 
 	// Init
 	srand((unsigned int)time(NULL));
 	rand_state rs = init_rand();
-	uint32_t sum = 0; // to avoid compiler optimizing out stuff
 
 	printf("Full range generation perf - %d number of cases:\n", N);
 
 	auto t0 = std::chrono::high_resolution_clock::now();
 
-	// rand
+	// arc4
 	for (int i = 0; i < N; ++i) {
-		sum += rand();
+		res[i] += arc4random();
 	}
 
 	auto t1 = std::chrono::high_resolution_clock::now();
 
-	// arc4
+	// rand
 	for (int i = 0; i < N; ++i) {
-		sum += arc4random();
+		res[i] += rand();
 	}
 
 	auto t2 = std::chrono::high_resolution_clock::now();
 
 	// lcg
 	for (int i = 0; i < N; ++i) {
-		sum += lcg(&rs);
+		res[i] += lcg(&rs);
 	}
 
 	auto t3 = std::chrono::high_resolution_clock::now();
 
 	// results 1
 
-	auto rand_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(t1 - t0);
-	auto arc4_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(t2 - t1);
+	auto arc4_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(t1 - t0);
+	auto rand_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(t2 - t1);
 	auto lcg_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(t3 - t2);
 
-	printf("Time (rand): %.3f ms.\n", rand_elapsed.count() * 1e-6);
 	printf("Time (arc4): %.3f ms.\n", arc4_elapsed.count() * 1e-6);
+	printf("Time (rand): %.3f ms.\n", rand_elapsed.count() * 1e-6);
 	printf("Time (lcg): %.3f ms.\n", lcg_elapsed.count() * 1e-6);
 
 	printf("Modulo VS nomod perf for rand_between (both LCG) - %d number of cases:\n", M);
 
+
 	auto t4 = std::chrono::high_resolution_clock::now();
 
-	// lcg + modulo
+	// rand + modulo
 	for (int i = 0; i < M; ++i) {
-		sum += FROM + (lcg(&rs) % (TO - FROM));
+		res[i] += FROM + (rand() % (TO - FROM));
 	}
 
 	auto t5 = std::chrono::high_resolution_clock::now();
 
-	// rand_between (also LCG, but no modulus)
+	// lcg + modulo
 	for (int i = 0; i < M; ++i) {
-		sum += rand_between(&rs, FROM, TO);
+		res[i] += FROM + (lcg(&rs) % (TO - FROM));
 	}
 
 	auto t6 = std::chrono::high_resolution_clock::now();
 
+	// rand_between (also LCG, but no modulus)
+	for (int i = 0; i < M; ++i) {
+		res[i] += rand_between(&rs, FROM, TO);
+	}
+
+	auto t7 = std::chrono::high_resolution_clock::now();
+
+
 	// results 2
 
-	auto mod_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(t5 - t4);
-	auto between_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(t6 - t5);
+	auto randmod_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(t5 - t4);
+	auto mod_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(t6 - t5);
+	auto between_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(t7 - t6);
 
 	uint32_t choice = rand_between(&rs, FROM, TO);
+	printf("rand + modulo [%u, %u): %.3f ms.\n", FROM, TO, randmod_elapsed.count() * 1e-6);
 	printf("lcg + modulo [%u, %u): %.3f ms.\n", FROM, TO, mod_elapsed.count() * 1e-6);
 	printf("rand_between [%u, %u): %.3f ms.\n", FROM, TO, between_elapsed.count() * 1e-6);
 
-	// checksum - avoid optimizing out loops
+	// checksum - avoids optimizing out above loops
 
+	uint32_t sum = 0;
+	for(int i = 0; i < M; ++i) {
+		sum += res[i];
+	}
 	printf("Checksum: 0x%x\n", sum);
 
 	return 0;