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Fix computing lower boundaries for smallest normalized double

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This commit is contained in:
Victor Zverovich
2019-10-18 16:55:07 -07:00
parent bb728a572a
commit 2bc5585ff0
2 changed files with 86 additions and 74 deletions
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test/format-impl-test.cc
+31 -30
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@@ -180,18 +180,40 @@ TEST(BigIntTest, DivModAssign) {
EXPECT_EQ("2a", fmt::format("{}", n2));
}
template <bool is_iec559> void test_construct_from_double() {
template <bool is_iec559> void run_double_tests() {
fmt::print("warning: double is not IEC559, skipping FP tests\n");
}
template <> void test_construct_from_double<true>() {
auto v = fp(1.23);
EXPECT_EQ(v.f, 0x13ae147ae147aeu);
EXPECT_EQ(v.e, -52);
template <> void run_double_tests<true>() {
// Construct from double.
EXPECT_EQ(fp(1.23), fp(0x13ae147ae147aeu, -52));
// Compute boundaries:
fp value, lower, upper;
// Normalized & not power of 2 - equidistant boundaries:
value.assign_with_boundaries(1.23, lower, upper);
EXPECT_EQ(value, fp(0x0013ae147ae147ae, -52));
EXPECT_EQ(lower, fp(0x9d70a3d70a3d6c00, -63));
EXPECT_EQ(upper, fp(0x9d70a3d70a3d7400, -63));
// Normalized power of 2 - lower boundary is closer:
value.assign_with_boundaries(1.9807040628566084e+28, lower, upper); // 2**94
EXPECT_EQ(value, fp(0x0010000000000000, 42));
EXPECT_EQ(lower, fp(0x7ffffffffffffe00, 31));
EXPECT_EQ(upper, fp(0x8000000000000400, 31));
// Smallest normalized double - equidistant boundaries:
value.assign_with_boundaries(2.2250738585072014e-308, lower, upper);
EXPECT_EQ(value, fp(0x0010000000000000, -1074));
EXPECT_EQ(lower, fp(0x7ffffffffffffc00, -1085));
EXPECT_EQ(upper, fp(0x8000000000000400, -1085));
// Subnormal - equidistant boundaries:
value.assign_with_boundaries(4.9406564584124654e-324, lower, upper);
EXPECT_EQ(value, fp(0x0000000000000001, -1074));
EXPECT_EQ(lower, fp(0x4000000000000000, -1137));
EXPECT_EQ(upper, fp(0xc000000000000000, -1137));
}
TEST(FPTest, ConstructFromDouble) {
test_construct_from_double<std::numeric_limits<double>::is_iec559>();
TEST(FPTest, DoubleTests) {
run_double_tests<std::numeric_limits<double>::is_iec559>();
}
TEST(FPTest, Normalize) {
@@ -201,26 +223,6 @@ TEST(FPTest, Normalize) {
EXPECT_EQ(-6, normalized.e);
}
TEST(FPTest, ComputeBoundariesSubnormal) {
auto v = fp(0xbeef, 42);
fp lower, upper;
v.compute_boundaries(lower, upper);
EXPECT_EQ(0xbeee800000000000, lower.f);
EXPECT_EQ(-6, lower.e);
EXPECT_EQ(0xbeef800000000000, upper.f);
EXPECT_EQ(-6, upper.e);
}
TEST(FPTest, ComputeBoundaries) {
auto v = fp(0x10000000000000, 42);
fp lower, upper;
v.compute_boundaries(lower, upper);
EXPECT_EQ(0x7ffffffffffffe00, lower.f);
EXPECT_EQ(31, lower.e);
EXPECT_EQ(0x8000000000000400, upper.f);
EXPECT_EQ(31, upper.e);
}
TEST(FPTest, ComputeFloatBoundaries) {
struct {
double x, lower, upper;
@@ -237,13 +239,12 @@ TEST(FPTest, ComputeFloatBoundaries) {
{1e-45f, 7.006492321624085e-46, 2.1019476964872256e-45},
};
for (auto test : tests) {
auto v = fp(test.x);
fp vlower = normalize(fp(test.lower));
fp vupper = normalize(fp(test.upper));
vlower.f >>= vupper.e - vlower.e;
vlower.e = vupper.e;
fp lower, upper;
v.compute_float_boundaries(lower, upper);
fp value, lower, upper;
value.assign_float_with_boundaries(test.x, lower, upper);
EXPECT_EQ(vlower.f, lower.f);
EXPECT_EQ(vlower.e, lower.e);
EXPECT_EQ(vupper.f, upper.f);