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#include <inttypes.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#define noinline __attribute__((__noinline__))
static inline uint64_t GetSystemClock() {
timespec ts;
// Assume clock_gettime() doesn't fail.
clock_gettime(CLOCK_MONOTONIC, &ts);
return ts.tv_sec * 1000000000ULL + ts.tv_nsec;
}
constexpr int LOOP_COUNT = 100000000;
uint64_t noinline RunFunction() {
uint64_t start_time_in_ns = GetSystemClock();
for (volatile int i = 0; i < LOOP_COUNT; ++i) {
}
return GetSystemClock() - start_time_in_ns;
}
uint64_t noinline SleepFunction(unsigned long long sleep_time_in_ns) {
uint64_t start_time_in_ns = GetSystemClock();
struct timespec req;
req.tv_sec = sleep_time_in_ns / 1000000000;
req.tv_nsec = sleep_time_in_ns % 1000000000;
nanosleep(&req, nullptr);
return GetSystemClock() - start_time_in_ns;
}
void noinline GlobalFunction() {
uint64_t total_sleep_time_in_ns = 0;
uint64_t total_run_time_in_ns = 0;
while (true) {
total_run_time_in_ns += RunFunction();
if (total_sleep_time_in_ns < total_run_time_in_ns) {
total_sleep_time_in_ns += SleepFunction(total_run_time_in_ns - total_sleep_time_in_ns);
}
}
}
int main() {
GlobalFunction();
return 0;
}
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