gists/c-programming/benchmarking/clock_hr_microsec.c

/*
 * clock_hr_microsec.c
 *
 * A small library to measure execution time of code as precisely as possible.
 *
 * TODO: Use fixed point arithmetics
 *
 * Author: Intel A80486DX2-66
 * License: Unlicense
 */

#include "clock_hr_microsec.h"

// macros
#if defined(SYS_NT)
static LONGLONG QPF_frequency;

# define WinAPI_perror_COMMON_MACRO \
      fprintf(stderr, "%s: %lu, %s", s, errorCode, errorString)
# define CLOCK_HR_DIFFTIME_MS(t2, t1)                                         \
      (((clock_hr_microsec_t) ((t2) - (t1))) /                                \
       ((clock_hr_microsec_t) QPF_frequency))

#elif defined(SYS_UNIX)
# define CLOCK_HR_DIFFTIME_MS(t2, t1)                                         \
      ((t2) - (t1))

#else
# define CLOCK_HR_DIFFTIME_MS(t2, t1)                                         \
      ((clock_hr_microsec_t) ((t2) - (t1)) * 1000000.L) /                             \
      ((clock_hr_microsec_t) CLOCKS_PER_SEC)

#endif

// function implementations
void clock_hr_microsec_init(void) {
# ifdef SYS_NT
	// set console output code page to the native one
	SetConsoleOutputCP(GetACP());

	// get CPU frequency
	LARGE_INTEGER freq;
	if (!QueryPerformanceFrequency(&freq)) {
		WinAPI_perror("QueryPerformanceFrequency");
		exit(EXIT_FAILURE);
	}

	QPF_frequency = freq.QuadPart;
# endif
}

long double clock_hr_microsec(void) {
# if defined(SYS_NT)
	// FIXME: less accurate than Unix

	LARGE_INTEGER counter;
	if (!QueryPerformanceCounter(&counter)) {
		WinAPI_perror("QueryPerformanceCounter");
		exit(EXIT_FAILURE);
	}
	return (long double) (counter.QuadPart * 1000000ULL);
# elif defined(SYS_UNIX)
	struct timespec ts;
	clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
	return ((long double) (ts.tv_sec * 1000000000ULL + ts.tv_nsec)) / 1000.l;
# else
	return (long double) (clock() * 1000000ULL);
# endif
}

clock_hr_microsec_t clock_hr_microsec_diff(clock_hr_microsec_t a,
                                           clock_hr_microsec_t b) {
	return CLOCK_HR_DIFFTIME_MS(a, b);
}

# ifdef SYS_NT
void WinAPI_perror(const char* s) {
	DWORD errorCode = GetLastError();
	LPSTR errorString = NULL;
	FormatMessage(
		FORMAT_MESSAGE_ALLOCATE_BUFFER |
		FORMAT_MESSAGE_FROM_SYSTEM |
		FORMAT_MESSAGE_IGNORE_INSERTS,
		NULL,
		errorCode,
		MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
		(LPSTR)&errorString,
		0,
		NULL
	);

	if (errorString == NULL) {
		errorString = "???\n";
		WinAPI_perror_COMMON_MACRO;
	} else {
		WinAPI_perror_COMMON_MACRO;
		LocalFree(errorString);
	}
}
# endif

#ifdef TEST
# include <stdio.h>

int main(void) {
	clock_hr_microsec_init();

	clock_hr_microsec_t t1 = 0, t2 = 0;

	t1 = clock_hr_microsec();

	int counter = 0;
	printf("[");
	for (int i = 1; i <= 240; i += 3, counter++) {
		if (i >= 8 && (counter & 7) == 0) {
			printf("\n ");
		}
		printf("0x%02X", i);

		if (i <= 237) {
			printf(", ");
		}
	}
	puts("]\n");

	t2 = clock_hr_microsec();

	printf("Counter = %d\n"
	       "Time: %" CLOCK_HR_MICROSEC_PRI " microsec\n",
	       counter,
	       clock_hr_microsec_diff(t2, t1));
}
#endif