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https://github.com/XRPLF/rippled.git
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fix: Fix a rounding error at the Number::maxRep cusp
- Add helper function, doDropDigit, to wrap the common pattern:
push(mantissa % 10);
mantissa /= 10;
++exponent;
- Might have been helpful to catch this issue when developing.
This commit is contained in:
Ed Hennis
@@ -4256,109 +4256,119 @@ class Invariants_test : public beast::unit_test::Suite
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std::vector<ValidVault::DeltaInfo> values;
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};
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NumberMantissaScaleGuard const g{MantissaRange::MantissaScale::Large};
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auto makeDelta = [&vaultAsset](Number const& n) -> ValidVault::DeltaInfo {
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return {.delta = n, .scale = scale(n, vaultAsset.raw())};
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};
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auto const testCases = std::vector<TestCase>{
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{
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.name = "No values",
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.expectedMinScale = 0,
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.values = {},
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},
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{
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.name = "Mixed integer and Number values",
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.expectedMinScale = -15,
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.values = {makeDelta(1), makeDelta(-1), makeDelta(Number{10, -1})},
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},
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{
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.name = "Mixed scales",
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.expectedMinScale = -17,
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.values =
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{makeDelta(Number{1, -2}), makeDelta(Number{5, -3}), makeDelta(Number{3, -2})},
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},
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{
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.name = "Equal scales",
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.expectedMinScale = -16,
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.values =
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{makeDelta(Number{1, -1}), makeDelta(Number{5, -1}), makeDelta(Number{1, -1})},
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},
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{
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.name = "Mixed mantissa sizes",
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.expectedMinScale = -12,
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.values =
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{makeDelta(Number{1}),
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makeDelta(Number{1234, -3}),
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makeDelta(Number{12345, -6}),
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makeDelta(Number{123, 1})},
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},
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};
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for (auto const& tc : testCases)
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for (auto const mantissaScale : {
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MantissaRange::MantissaScale::LargeLegacy,
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MantissaRange::MantissaScale::Large,
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})
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{
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testcase("vault computeCoarsestScale: " + tc.name);
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NumberMantissaScaleGuard const g{mantissaScale};
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auto const actualScale = ValidVault::computeCoarsestScale(tc.values);
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auto makeDelta = [&vaultAsset](Number const& n) -> ValidVault::DeltaInfo {
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return {.delta = n, .scale = scale(n, vaultAsset.raw())};
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};
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BEAST_EXPECTS(
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actualScale == tc.expectedMinScale,
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"expected: " + std::to_string(tc.expectedMinScale) +
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", actual: " + std::to_string(actualScale));
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for (auto const& num : tc.values)
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{
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// None of these scales are far enough apart that rounding the
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// values would lose information, so check that the rounded
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// value matches the original.
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auto const actualRounded = roundToAsset(vaultAsset, num.delta, actualScale);
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BEAST_EXPECTS(
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actualRounded == num.delta,
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"number " + to_string(num.delta) + " rounded to scale " +
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std::to_string(actualScale) + " is " + to_string(actualRounded));
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}
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}
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auto const testCases2 = std::vector<TestCase>{
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{
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.name = "False equivalence",
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.expectedMinScale = -15,
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.values =
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{
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makeDelta(Number{1234567890123456789, -18}),
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makeDelta(Number{12345, -4}),
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makeDelta(Number{1}),
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},
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},
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};
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// Unlike the first set of test cases, the values in these test could
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// look equivalent if using the wrong scale.
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for (auto const& tc : testCases2)
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{
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testcase("vault computeCoarsestScale: " + tc.name);
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auto const actualScale = ValidVault::computeCoarsestScale(tc.values);
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BEAST_EXPECTS(
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actualScale == tc.expectedMinScale,
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"expected: " + std::to_string(tc.expectedMinScale) +
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", actual: " + std::to_string(actualScale));
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std::optional<Number> first;
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Number firstRounded;
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for (auto const& num : tc.values)
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{
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if (!first)
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auto const testCases = std::vector<TestCase>{
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{
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first = num.delta;
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firstRounded = roundToAsset(vaultAsset, num.delta, actualScale);
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continue;
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}
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auto const numRounded = roundToAsset(vaultAsset, num.delta, actualScale);
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.name = "No values",
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.expectedMinScale = 0,
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.values = {},
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},
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{
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.name = "Mixed integer and Number values",
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.expectedMinScale = -15,
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.values = {makeDelta(1), makeDelta(-1), makeDelta(Number{10, -1})},
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},
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{
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.name = "Mixed scales",
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.expectedMinScale = -17,
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.values =
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{makeDelta(Number{1, -2}),
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makeDelta(Number{5, -3}),
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makeDelta(Number{3, -2})},
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},
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{
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.name = "Equal scales",
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.expectedMinScale = -16,
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.values =
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{makeDelta(Number{1, -1}),
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makeDelta(Number{5, -1}),
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makeDelta(Number{1, -1})},
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},
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{
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.name = "Mixed mantissa sizes",
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.expectedMinScale = -12,
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.values =
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{makeDelta(Number{1}),
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makeDelta(Number{1234, -3}),
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makeDelta(Number{12345, -6}),
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makeDelta(Number{123, 1})},
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},
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};
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for (auto const& tc : testCases)
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{
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testcase("vault computeCoarsestScale: " + tc.name);
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auto const actualScale = ValidVault::computeCoarsestScale(tc.values);
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BEAST_EXPECTS(
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numRounded != firstRounded,
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"at a scale of " + std::to_string(actualScale) + " " + to_string(num.delta) +
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" == " + to_string(*first));
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actualScale == tc.expectedMinScale,
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"expected: " + std::to_string(tc.expectedMinScale) +
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", actual: " + std::to_string(actualScale));
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for (auto const& num : tc.values)
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{
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// None of these scales are far enough apart that rounding the
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// values would lose information, so check that the rounded
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// value matches the original.
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auto const actualRounded = roundToAsset(vaultAsset, num.delta, actualScale);
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BEAST_EXPECTS(
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actualRounded == num.delta,
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"number " + to_string(num.delta) + " rounded to scale " +
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std::to_string(actualScale) + " is " + to_string(actualRounded));
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}
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}
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auto const testCases2 = std::vector<TestCase>{
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{
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.name = "False equivalence",
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.expectedMinScale = -15,
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.values =
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{
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makeDelta(Number{1234567890123456789, -18}),
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makeDelta(Number{12345, -4}),
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makeDelta(Number{1}),
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},
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},
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};
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// Unlike the first set of test cases, the values in these test could
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// look equivalent if using the wrong scale.
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for (auto const& tc : testCases2)
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{
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testcase("vault computeCoarsestScale: " + tc.name);
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auto const actualScale = ValidVault::computeCoarsestScale(tc.values);
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BEAST_EXPECTS(
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actualScale == tc.expectedMinScale,
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"expected: " + std::to_string(tc.expectedMinScale) +
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", actual: " + std::to_string(actualScale));
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std::optional<Number> first;
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Number firstRounded;
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for (auto const& num : tc.values)
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{
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if (!first)
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{
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first = num.delta;
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firstRounded = roundToAsset(vaultAsset, num.delta, actualScale);
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continue;
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}
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auto const numRounded = roundToAsset(vaultAsset, num.delta, actualScale);
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BEAST_EXPECTS(
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numRounded != firstRounded,
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"at a scale of " + std::to_string(actualScale) + " " +
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to_string(num.delta) + " == " + to_string(*first));
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}
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}
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}
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}
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