Export of internal Abseil changes

--
a74bdb72c3a6983e08a805938dd0e20e97d55bba by Abseil Team <absl-team@google.com>:

Fix typo: calcualte -> calculate

PiperOrigin-RevId: 360515509

--
3ddf8ac194e81a13e9de095e59dd061c1beacfe3 by Benjamin Barenblat <bbaren@google.com>:

Make tests tolerant of FMA contraction

Weaken Duration.ToDoubleSecondsCheckEdgeCases and
Duration.ToDoubleSecondsCheckRandom to make them less sensitive to fused
multiply/add contraction.

PiperOrigin-RevId: 360297653
GitOrigin-RevId: a74bdb72c3a6983e08a805938dd0e20e97d55bba
Change-Id: I0c55383bc13040ea77511c4130d142368103dc57
pull/915/head
Abseil Team 4 years ago committed by Matt Kulukundis
parent a766987907
commit b0735979d7
  1. 2
      absl/numeric/internal/bits.h
  2. 18
      absl/time/duration_test.cc

@ -343,7 +343,7 @@ ABSL_ATTRIBUTE_ALWAYS_INLINE ABSL_INTERNAL_CONSTEXPR_CLZ inline
typename std::enable_if<std::is_unsigned<T>::value, T>::type
BitCeilNonPowerOf2(T x) {
// If T is narrower than unsigned, it undergoes promotion to unsigned when we
// shift. We calcualte the number of bits added by the wider type.
// shift. We calculate the number of bits added by the wider type.
return BitCeilPromotionHelper(
static_cast<T>(std::numeric_limits<T>::digits - CountLeadingZeroes(x)),
T{sizeof(T) >= sizeof(unsigned) ? 0

@ -1369,10 +1369,13 @@ TEST(Duration, SmallConversions) {
EXPECT_THAT(ToTimeval(absl::Nanoseconds(2000)), TimevalMatcher(tv));
}
void VerifySameAsMul(double time_as_seconds, int* const misses) {
void VerifyApproxSameAsMul(double time_as_seconds, int* const misses) {
auto direct_seconds = absl::Seconds(time_as_seconds);
auto mul_by_one_second = time_as_seconds * absl::Seconds(1);
if (direct_seconds != mul_by_one_second) {
// These are expected to differ by up to one tick due to fused multiply/add
// contraction.
if (absl::AbsDuration(direct_seconds - mul_by_one_second) >
absl::time_internal::MakeDuration(0, 1u)) {
if (*misses > 10) return;
ASSERT_LE(++(*misses), 10) << "Too many errors, not reporting more.";
EXPECT_EQ(direct_seconds, mul_by_one_second)
@ -1384,7 +1387,8 @@ void VerifySameAsMul(double time_as_seconds, int* const misses) {
// For a variety of interesting durations, we find the exact point
// where one double converts to that duration, and the very next double
// converts to the next duration. For both of those points, verify that
// Seconds(point) returns the same duration as point * Seconds(1.0)
// Seconds(point) returns a duration near point * Seconds(1.0). (They may
// not be exactly equal due to fused multiply/add contraction.)
TEST(Duration, ToDoubleSecondsCheckEdgeCases) {
constexpr uint32_t kTicksPerSecond = absl::time_internal::kTicksPerSecond;
constexpr auto duration_tick = absl::time_internal::MakeDuration(0, 1u);
@ -1423,8 +1427,8 @@ TEST(Duration, ToDoubleSecondsCheckEdgeCases) {
}
// Now low_edge is the highest double that converts to Duration d,
// and high_edge is the lowest double that converts to Duration after_d.
VerifySameAsMul(low_edge, &misses);
VerifySameAsMul(high_edge, &misses);
VerifyApproxSameAsMul(low_edge, &misses);
VerifyApproxSameAsMul(high_edge, &misses);
}
}
}
@ -1444,8 +1448,8 @@ TEST(Duration, ToDoubleSecondsCheckRandom) {
int misses = 0;
for (int i = 0; i < 1000000; ++i) {
double d = std::exp(uniform(gen));
VerifySameAsMul(d, &misses);
VerifySameAsMul(-d, &misses);
VerifyApproxSameAsMul(d, &misses);
VerifyApproxSameAsMul(-d, &misses);
}
}

Loading…
Cancel
Save