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Fix flaky TestBasicTimerFunctionality on Windows #3463

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Fix flaky TestBasicTimerFunctionality on Windows #3463

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39 changes: 19 additions & 20 deletions tensorflow/lite/micro/micro_time_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -18,29 +18,28 @@ limitations under the License.
#include "tensorflow/lite/micro/testing/micro_test_v2.h"

TEST(MicroTimeTest, TestBasicTimerFunctionality) {
uint32_t ticks_per_second = tflite::ticks_per_second();

// Retry enough times to guarantee a tick advance, while not taking too long
// to complete. With 1e6 retries, assuming each loop takes tens of cycles,
// this will retry for less than 10 seconds on a 10MHz platform.
constexpr int kMaxRetries = 1e6;
unsigned int start_time = tflite::GetCurrentTimeTicks();

if (ticks_per_second != 0) {
for (int i = 0; i < kMaxRetries; i++) {
if (tflite::GetCurrentTimeTicks() - start_time > 0) {
break;
}
const uint32_t ticks_per_second = tflite::ticks_per_second();

// If the platform does not implement a timer, skip the test.
if (ticks_per_second == 0) {
return;
}

const auto start_time = tflite::GetCurrentTimeTicks();

// HARDENING: Increase retries to handle fast CPUs on platforms with low
// timer resolution (e.g., Windows ~15ms). 100 million iterations guarantees
// the loop exceeds the duration of a single tick.
constexpr int kMaxRetries = 100000000;

for (volatile int i = 0; i < kMaxRetries; i++) {
if (tflite::GetCurrentTimeTicks() != start_time) {
break;
}
}

// Ensure the timer is increasing. This works for the overflow case too, since
// (MIN_INT + x) - (MAX_INT - y) == x + y + 1. For example,
// 0x80000001(min int + 1) - 0x7FFFFFFE(max int - 1) = 0x00000003 == 3.
// GetTicksPerSecond() == 0 means the timer is not implemented on this
// platform.
EXPECT_TRUE(ticks_per_second == 0 ||
tflite::GetCurrentTimeTicks() - start_time > 0);
// Verify that time has actually advanced.
EXPECT_GT(tflite::GetCurrentTimeTicks(), start_time);
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@ddavis-2015 ddavis-2015 Feb 25, 2026 •
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This doesn't account for hardware timer rollover. Maybe just skip this check altogether, as the for loop accounts for the hardware timer advancing?

}

TF_LITE_MICRO_TESTS_MAIN