From: Siva Chandra Reddy Date: Thu, 30 Apr 2020 17:02:09 +0000 (-0700) Subject: [libc] Fix how math results are compared with MPFR results. X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=a7e11496996269fc589322da7bedbe4b1adcb13f;p=platform%2Fupstream%2Fllvm.git [libc] Fix how math results are compared with MPFR results. Summary: Math results are compared with MPFR results by checking if they are within a tolerance level of the MPFR result. The tolerance level is set using additional bits of precision of the fractional part of a floating point value. Hence, the actual value of the tolerance depends on not only the additional bits, but also on the exponent part of the floating point number. Previously, the exponent part was not considered in evaluating the tolerance value. While it was OK for small values less than 1 (hence sinf, cosf, sincosf tests were OK), it breaks for large values which functions like exp and friends produce. This change uses the exponent value also to evaluate the tolerance value. LLVM libc produced results can now be compared with MPFR produced results for large values also. Reviewers: abrachet Differential Revision: https://reviews.llvm.org/D79278 --- diff --git a/libc/utils/MPFRWrapper/MPFRUtils.cpp b/libc/utils/MPFRWrapper/MPFRUtils.cpp index 75ee2ad..980557a 100644 --- a/libc/utils/MPFRWrapper/MPFRUtils.cpp +++ b/libc/utils/MPFRWrapper/MPFRUtils.cpp @@ -8,15 +8,55 @@ #include "MPFRUtils.h" +#include "llvm/ADT/StringExtras.h" #include "llvm/ADT/StringRef.h" #include +#include #include namespace __llvm_libc { namespace testing { namespace mpfr { +template struct FloatProperties {}; + +template <> struct FloatProperties { + typedef uint32_t BitsType; + static_assert(sizeof(BitsType) == sizeof(float), + "Unexpected size of 'float' type."); + + static constexpr uint32_t mantissaWidth = 23; + static constexpr BitsType signMask = 0x7FFFFFFFU; + static constexpr uint32_t exponentOffset = 127; +}; + +template <> struct FloatProperties { + typedef uint64_t BitsType; + static_assert(sizeof(BitsType) == sizeof(double), + "Unexpected size of 'double' type."); + + static constexpr uint32_t mantissaWidth = 52; + static constexpr BitsType signMask = 0x7FFFFFFFFFFFFFFFULL; + static constexpr uint32_t exponentOffset = 1023; +}; + +template typename FloatProperties::BitsType getBits(T x) { + using BitsType = typename FloatProperties::BitsType; + return *reinterpret_cast(&x); +} + +// Returns the zero adjusted exponent value of abs(x). +template int getExponent(T x) { + using Properties = FloatProperties; + using BitsType = typename Properties::BitsType; + BitsType bits = *reinterpret_cast(&x); + bits &= Properties::signMask; // Zero the sign bit. + int e = (bits >> Properties::mantissaWidth); // Shift out the mantissa. + e -= Properties::exponentOffset; // Zero adjust. + return e; +} + class MPFRNumber { // A precision value which allows sufficiently large additional // precision even compared to double precision floating point values. @@ -45,6 +85,38 @@ public: } template ::Value, int> = 0> + explicit MPFRNumber(XType x) { + mpfr_init2(value, mpfrPrecision); + mpfr_set_sj(value, x, MPFR_RNDN); + } + + template MPFRNumber(XType x, const Tolerance &t) { + mpfr_init2(value, mpfrPrecision); + mpfr_set_zero(value, 1); // Set to positive zero. + MPFRNumber xExponent(getExponent(x)); + // E = 2^E + mpfr_exp2(xExponent.value, xExponent.value, MPFR_RNDN); + uint32_t bitMask = 1 << (t.width - 1); + for (int n = -t.basePrecision; bitMask > 0; bitMask >>= 1) { + --n; + if (t.bits & bitMask) { + // delta = -n + MPFRNumber delta(n); + + // delta = 2^(-n) + mpfr_exp2(delta.value, delta.value, MPFR_RNDN); + + // delta = E * 2^(-n) + mpfr_mul(delta.value, delta.value, xExponent.value, MPFR_RNDN); + + // tolerance += delta + mpfr_add(value, value, delta.value, MPFR_RNDN); + } + } + } + + template ::Value, int> = 0> MPFRNumber(Operation op, XType rawValue) { mpfr_init2(value, mpfrPrecision); @@ -65,20 +137,9 @@ public: ~MPFRNumber() { mpfr_clear(value); } - // Returns true if |other| is within the tolerance value |t| of this + // Returns true if |other| is within the |tolerance| value of this // number. - bool isEqual(const MPFRNumber &other, const Tolerance &t) { - MPFRNumber tolerance(0.0); - uint32_t bitMask = 1 << (t.width - 1); - for (int exponent = -t.basePrecision; bitMask > 0; bitMask >>= 1) { - --exponent; - if (t.bits & bitMask) { - MPFRNumber delta; - mpfr_set_ui_2exp(delta.value, 1, exponent, MPFR_RNDN); - mpfr_add(tolerance.value, tolerance.value, delta.value, MPFR_RNDN); - } - } - + bool isEqual(const MPFRNumber &other, const MPFRNumber &tolerance) const { MPFRNumber difference; if (mpfr_cmp(value, other.value) >= 0) mpfr_sub(difference.value, value, other.value, MPFR_RNDN); @@ -112,10 +173,14 @@ void MPFRMatcher::explainError(testutils::StreamWrapper &OS) { MPFRNumber mpfrResult(operation, input); MPFRNumber mpfrInput(input); MPFRNumber mpfrMatchValue(matchValue); + MPFRNumber mpfrToleranceValue(matchValue, tolerance); OS << "Match value not within tolerance value of MPFR result:\n" - << "Operation input: " << mpfrInput.str() << '\n' - << " Match value: " << mpfrMatchValue.str() << '\n' - << " MPFR result: " << mpfrResult.str() << '\n'; + << " Input decimal: " << mpfrInput.str() << '\n' + << " Input bits: 0x" << llvm::utohexstr(getBits(input)) << '\n' + << " Match decimal: " << mpfrMatchValue.str() << '\n' + << " Match bits: 0x" << llvm::utohexstr(getBits(matchValue)) << '\n' + << " MPFR result: " << mpfrResult.str() << '\n' + << "Tolerance value: " << mpfrToleranceValue.str() << '\n'; } template void MPFRMatcher::explainError(testutils::StreamWrapper &); @@ -124,9 +189,10 @@ template void MPFRMatcher::explainError(testutils::StreamWrapper &); template bool compare(Operation op, T input, T libcResult, const Tolerance &t) { MPFRNumber mpfrResult(op, input); - MPFRNumber mpfrInput(input); MPFRNumber mpfrLibcResult(libcResult); - return mpfrResult.isEqual(mpfrLibcResult, t); + MPFRNumber mpfrToleranceValue(libcResult, t); + + return mpfrResult.isEqual(mpfrLibcResult, mpfrToleranceValue); }; template bool compare(Operation, float, float, const Tolerance &);