improve descriptive stats

Makefile

@@ -10,14 +10,20 @@ LDFLAGS := -luring -pthread -lrt -lm
 CFLAGS := -Werror -Wall -g -O3
 # CFLAGS := -Werror -Wall -g -O0
 
-.PHONY: all clean eval docker-eval check
+.PHONY: all clean eval eval-stats docker-eval docker-eval-stats check
 
 eval: all
-	@for syscall in $(SYSCALLS); do echo -n "$$syscall " ; ./bench-$$syscall $(STATS); done
+	@for syscall in $(SYSCALLS); do ./bench-$$syscall $(STATS); done
+
+eval-stats:
+	@$(MAKE) STATS=--stats eval
 
 docker-eval:
 	./docker.sh make eval
 
+docker-eval-stats:
+	./docker.sh make eval-stats
+
 all: $(OBJ)
 
 define generateTargets

bench.c

@@ -49,17 +49,18 @@ int main(int argc, char *argv[]) {
 
 	for (int64_t i = 1; i <= exp_iterations; ++i) {
 		do_write(fd, &write_buf, sizeof(write_buf));
-		nanos[i] = clock_diff_nanos();
-		cycles[i] = clock_diff_cycles();
+		nanos[i - 1] = clock_diff_nanos();
+		cycles[i - 1] = clock_diff_cycles();
 	}
 
 	if (print_stats) {
-		print_desc_stats("nanos", nanos, exp_iterations);
-		print_desc_stats("cycles", cycles, exp_iterations);
+		printf("%s:\n", argv[0]);
+		print_desc_stats("nanos", "  ", nanos, exp_iterations);
+		print_desc_stats("cycles", "  ", cycles, exp_iterations);
 	} else {
 		uint64_t avg_nanos = calc_mean(nanos, exp_iterations);
 		uint64_t avg_cycles = calc_mean(cycles, exp_iterations);
-		printf("avg-nanos: %lu, avg-cycles: %lu\n", avg_nanos, avg_cycles);
+		printf("%s avg-nanos: %lu, avg-cycles: %lu\n", argv[0], avg_nanos, avg_cycles);
 	}
 
 	free(nanos);

stats.c

@@ -5,7 +5,7 @@
 #include <stdint.h>
 #include <stdio.h>
 
-uint64_t calc_median(uint64_t* data, size_t size) {
+uint64_t calc_median(const uint64_t* data, size_t size) {
 	// sample size is odd -> there is a middle value
 	if (size % 2 == 1) return data[size / 2];
 
@@ -15,7 +15,12 @@ uint64_t calc_median(uint64_t* data, size_t size) {
 	return before_median + ((after_median - before_median) / 2);
 }
 
-uint64_t calc_mean(uint64_t* data, size_t size) {
+static void check_saple_size(size_t size) {
+	if (size == 0) errx(EXIT_FAILURE, "data size must not be zero");
+}
+
+uint64_t calc_mean(const uint64_t* data, size_t size) {
+	check_saple_size(size);
 	uint64_t sum = 0;
 	for (size_t i = 0; i < size; ++i) {
 		if (__builtin_add_overflow(sum, data[i], &sum)) errx(EXIT_FAILURE, "sum overflowed at %ld", i);
@@ -23,10 +28,11 @@ uint64_t calc_mean(uint64_t* data, size_t size) {
 	return sum / size;
 }
 
-uint64_t calc_var(uint64_t* data, size_t size, uint64_t mean) {
+uint64_t calc_var(const uint64_t* data, size_t size, uint64_t mean) {
+	check_saple_size(size);
 	uint64_t sum = 0;
 	for (size_t i = 0; i < size; ++i) {
-		const int64_t delta = mean - data[i];
+		const uint64_t delta = mean - data[i];
 		const uint64_t delta_pow = (uint64_t)pow((double)delta, 2);
 		if (__builtin_add_overflow(sum, delta_pow, &sum))
 			errx(EXIT_FAILURE, "sum overflowed at %ld", i);
@@ -44,9 +50,10 @@ static int compare_uint64_t(const void* v1, const void* v2) {
 	return 0;
 }
 
-void print_desc_stats(const char* name, uint64_t* data, size_t size) {
+void print_desc_stats(const char* name, const char* indentation, const uint64_t* data,
+											size_t size) {
 	// sort our data
-	qsort(data, size, sizeof(uint64_t), compare_uint64_t);
+	qsort((void*)data, size, sizeof(uint64_t), compare_uint64_t);
 
 	const uint64_t min = data[0];
 	const uint64_t max = data[size - 1];
@@ -55,10 +62,11 @@ void print_desc_stats(const char* name, uint64_t* data, size_t size) {
 	const uint64_t var = calc_var(data, size, mean);
 	const uint64_t std = (uint64_t)sqrt((double)var);
 
-	printf("%s-min: %lu\n", name, min);
-	printf("%s-max: %lu\n", name, max);
-	printf("%s-median: %lu\n", name, median);
-	printf("%s-mean: %lu\n", name, mean);
-	printf("%s-var: %lu\n", name, var);
-	printf("%s-std: %lu\n", name, std);
+	printf("%s%s\n", indentation, name);
+	printf("%s%smin: %lu\n", indentation, indentation, min);
+	printf("%s%smax: %lu\n", indentation, indentation, max);
+	printf("%s%smedian: %lu\n", indentation, indentation, median);
+	printf("%s%smean: %lu\n", indentation, indentation, mean);
+	printf("%s%svar: %lu\n", indentation, indentation, var);
+	printf("%s%sstd: %lu\n", indentation, indentation, std);
 }

stats.h

@@ -3,7 +3,7 @@
 #include "stdint.h"
 #include "stdlib.h"
 
-uint64_t calc_mean(uint64_t* data, size_t size);
-uint64_t calc_median(uint64_t* data, size_t size);
-uint64_t calc_var(uint64_t* data, size_t size, uint64_t mean);
-void print_desc_stats(const char* name, uint64_t* data, size_t size);
\ No newline at end of file
+uint64_t calc_mean(const uint64_t* data, size_t size);
+uint64_t calc_median(const uint64_t* data, size_t size);
+uint64_t calc_var(const uint64_t* data, size_t size, uint64_t mean);
+void print_desc_stats(const char* name, const char* indentation, const uint64_t* data, size_t size);
\ No newline at end of file