From 44efe96dfca674a17b45ca53fc77fb69f1e29bf4 Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Tue, 9 Jul 2019 07:37:37 -0700 Subject: Export of internal Abseil changes. -- 9c4ef32276054fba6a116c01cd4b3fd278f59ece by Andy Soffer : Remove support for unused arbitrary-width output in FastUniformBits. Width should be inferred from the requested return UIntType. PiperOrigin-RevId: 257189319 -- e3326329d02171a301cc3d6ae617ed448472b728 by Abseil Team : Update comments to make clear that absl::Format(std::string *, ...) appends to the provided string. PiperOrigin-RevId: 257058043 -- e2096b06d714fba3ea2c885d670a42efd872765c by Xiaoyi Zhang : Fix compilation error on MSVC 2017. The root cause seems to be a compiler bug in VS 2017 about pack expansion with multiple parameter packs, specifically `MakeVisitationMatrixImpl::Run` is triggering compiler error "error C3528: 'BoundIndices': the number of elements in this pack expansion does not match the number of elements in 'EndIndices'". Work around this issue by using only one parameter pack `CurrIndices` in `MakeVisitationMatrixImpl::Run`. PiperOrigin-RevId: 257040381 -- 9ab75ff27b2513583fffc1233e6568aa96be36f7 by Matt Calabrese : Internal change. PiperOrigin-RevId: 257039041 GitOrigin-RevId: 9c4ef32276054fba6a116c01cd4b3fd278f59ece Change-Id: I5f708bb03aff93948502394a413260af2a8a273b --- absl/random/internal/fast_uniform_bits.h | 52 +++++++++++--------------------- 1 file changed, 17 insertions(+), 35 deletions(-) (limited to 'absl/random/internal/fast_uniform_bits.h') diff --git a/absl/random/internal/fast_uniform_bits.h b/absl/random/internal/fast_uniform_bits.h index 23eabbc8444c..184a2708b2af 100644 --- a/absl/random/internal/fast_uniform_bits.h +++ b/absl/random/internal/fast_uniform_bits.h @@ -38,14 +38,12 @@ constexpr typename URBG::result_type constexpr_range() { // from a type which conforms to the [rand.req.urbg] concept. // Parameterized by: // `UIntType`: the result (output) type -// `Width`: binary output width // // The std::independent_bits_engine [rand.adapt.ibits] adaptor can be // instantiated from an existing generator through a copy or a move. It does // not, however, facilitate the production of pseudorandom bits from an un-owned // generator that will outlive the std::independent_bits_engine instance. -template ::digits> +template class FastUniformBits { static_assert(std::is_unsigned::value, "Class-template FastUniformBits<> must be parameterized using " @@ -53,29 +51,14 @@ class FastUniformBits { // `kWidth` is the width, in binary digits, of the output. By default it is // the number of binary digits in the `result_type`. - static constexpr size_t kWidth = Width; - static_assert(kWidth > 0, - "Class-template FastUniformBits<> Width argument must be > 0"); - - static_assert(kWidth <= std::numeric_limits::digits, - "Class-template FastUniformBits<> Width argument must be <= " - "width of UIntType."); - - static constexpr bool kIsMaxWidth = - (kWidth >= std::numeric_limits::digits); - - // Computes a mask of `n` bits for the `UIntType`. - static constexpr UIntType constexpr_mask(size_t n) { - return (UIntType(1) << n) - 1; - } + static constexpr size_t kWidth = std::numeric_limits::digits; public: using result_type = UIntType; static constexpr result_type(min)() { return 0; } static constexpr result_type(max)() { - return kIsMaxWidth ? (std::numeric_limits::max)() - : constexpr_mask(kWidth); + return (std::numeric_limits::max)(); } template @@ -166,7 +149,6 @@ class FastUniformBitsURBGConstants { // URBG::result_type values are combined into an output_value. // Parameterized by the FastUniformBits parameters: // `UIntType`: output type. -// `Width`: binary output width, // `URNG`: The underlying UniformRandomNumberGenerator. // // The looping constants describe the sets of loop counters and mask values @@ -177,10 +159,10 @@ class FastUniformBitsURBGConstants { // bit per variate. // // See [rand.adapt.ibits] for more details on the use of these constants. -template +template class FastUniformBitsLoopingConstants { private: - static constexpr size_t kWidth = Width; + static constexpr size_t kWidth = std::numeric_limits::digits; using urbg_result_type = typename URBG::result_type; using uint_result_type = UIntType; @@ -229,19 +211,19 @@ class FastUniformBitsLoopingConstants { "Class-template FastUniformBitsLoopingConstants::kW0 too small."); }; -template +template template -typename FastUniformBits::result_type -FastUniformBits::operator()( +typename FastUniformBits::result_type +FastUniformBits::operator()( URBG& g) { // NOLINT(runtime/references) using constants = FastUniformBitsURBGConstants; return Generate( g, std::integral_constant= (max)()>{}); } -template +template template -typename URBG::result_type FastUniformBits::Variate( +typename URBG::result_type FastUniformBits::Variate( URBG& g) { // NOLINT(runtime/references) using constants = FastUniformBitsURBGConstants; if (constants::kPowerOfTwo) { @@ -256,10 +238,10 @@ typename URBG::result_type FastUniformBits::Variate( return u; } -template +template template -typename FastUniformBits::result_type -FastUniformBits::Generate( +typename FastUniformBits::result_type +FastUniformBits::Generate( URBG& g, // NOLINT(runtime/references) std::true_type /* avoid_looping */) { // The width of the result_type is less than than the width of the random bits @@ -268,10 +250,10 @@ FastUniformBits::Generate( return Variate(g) & (max)(); } -template +template template -typename FastUniformBits::result_type -FastUniformBits::Generate( +typename FastUniformBits::result_type +FastUniformBits::Generate( URBG& g, // NOLINT(runtime/references) std::false_type /* avoid_looping */) { // The width of the result_type is wider than the number of random bits @@ -279,7 +261,7 @@ FastUniformBits::Generate( // using a shift and mask. The constants type generates the parameters used // ensure that the bits are distributed across all the invocations of the // underlying URNG. - using constants = FastUniformBitsLoopingConstants; + using constants = FastUniformBitsLoopingConstants; result_type s = 0; for (size_t n = 0; n < constants::kN0; ++n) { -- cgit 1.4.1