js8544 commented on code in PR #36667:
URL: https://github.com/apache/arrow/pull/36667#discussion_r1266066589
##########
cpp/src/arrow/util/decimal_test.cc:
##########
@@ -1119,6 +1137,35 @@ class TestDecimalToReal : public ::testing::Test {
// 2**64 + 2**41 (exactly representable in a float)
CheckDecimalToReal<Decimal, Real>("18446746272732807168", 0,
1.8446746e+19f);
CheckDecimalToReal<Decimal, Real>("-18446746272732807168", 0,
-1.8446746e+19f);
+
+ // Integers are always exact
+ auto scale = Decimal::kMaxScale - 1;
+ std::string seven = "7.";
+ for (int32_t i = 0; i < scale; ++i) {
+ seven += "0";
+ }
+ CheckDecimalToReal<Decimal, Real>(seven, scale, 7.0f);
+ CheckDecimalToReal<Decimal, Real>("-" + seven, scale, -7.0f);
+
+ CheckDecimalToReal<Decimal, Real>("99999999999999999999.0000000000000000",
16,
+ 99999999999999999999.0f);
+ CheckDecimalToReal<Decimal,
Real>("-99999999999999999999.0000000000000000", 16,
+ -99999999999999999999.0f);
+
+ // Small fractions are within one ULP
+ CheckDecimalToRealWithinOneULP<Decimal, Real>("9999999.9", 1, 9999999.9f);
+ CheckDecimalToRealWithinOneULP<Decimal, Real>("-9999999.9", 1,
-9999999.9f);
+ CheckDecimalToRealWithinOneULP<Decimal, Real>("9999999.999999", 6,
9999999.999999f);
+ CheckDecimalToRealWithinOneULP<Decimal, Real>("-9999999.999999", 6,
-9999999.999999f);
+
+ // Large fractions are within 2^-23
+ constexpr Real epsilon = 1.1920928955078125e-07f; // 2^-23
+ CheckDecimalToRealWithinEpsilon<Decimal, Real>(
+ "112334829348925.99070703983306884765625", 23, epsilon,
+ 112334829348925.99070703983306884765625f);
Review Comment:
Yes, `double` is tested in TestDecimalToRealDouble::Precision. I added a
static_assert at the beginning to make it clearer.
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