tvl-depot/absl/random/internal/gaussian_distribution_gentables.cc

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Export of internal Abseil changes. -- 7a6ff16a85beb730c172d5d25cf1b5e1be885c56 by Laramie Leavitt <lar@google.com>: Internal change. PiperOrigin-RevId: 254454546 -- ff8f9bafaefc26d451f576ea4a06d150aed63f6f by Andy Soffer <asoffer@google.com>: Internal changes PiperOrigin-RevId: 254451562 -- deefc5b651b479ce36f0b4ef203e119c0c8936f2 by CJ Johnson <johnsoncj@google.com>: Account for subtracting unsigned values from the size of InlinedVector PiperOrigin-RevId: 254450625 -- 3c677316a27bcadc17e41957c809ca472d5fef14 by Andy Soffer <asoffer@google.com>: Add C++17's std::make_from_tuple to absl/utility/utility.h PiperOrigin-RevId: 254411573 -- 4ee3536a918830eeec402a28fc31a62c7c90b940 by CJ Johnson <johnsoncj@google.com>: Adds benchmark for the rest of the InlinedVector public API PiperOrigin-RevId: 254408378 -- e5a21a00700ee83498ff1efbf649169756463ee4 by CJ Johnson <johnsoncj@google.com>: Updates the definition of InlinedVector::shrink_to_fit() to be exception safe and adds exception safety tests for it. PiperOrigin-RevId: 254401387 -- 2ea82e72b86d82d78b4e4712a63a55981b53c64b by Laramie Leavitt <lar@google.com>: Use absl::InsecureBitGen in place of std::mt19937 in tests absl/random/...distribution_test.cc PiperOrigin-RevId: 254289444 -- fa099e02c413a7ffda732415e8105cad26a90337 by Andy Soffer <asoffer@google.com>: Internal changes PiperOrigin-RevId: 254286334 -- ce34b7f36933b30cfa35b9c9a5697a792b5666e4 by Andy Soffer <asoffer@google.com>: Internal changes PiperOrigin-RevId: 254273059 -- 6f9c473da7c2090c2e85a37c5f00622e8a912a89 by Jorg Brown <jorg@google.com>: Change absl::container_internal::CompressedTuple to instantiate its internal Storage class with the name of the type it's holding, rather than the name of the Tuple. This is not an externally-visible change, other than less compiler memory is used and less debug information is generated. PiperOrigin-RevId: 254269285 -- 8bd3c186bf2fc0c55d8a2dd6f28a5327502c9fba by Andy Soffer <asoffer@google.com>: Adding short-hand IntervalClosed for IntervalClosedClosed and IntervalOpen for IntervalOpenOpen. PiperOrigin-RevId: 254252419 -- ea957f99b6a04fccd42aa05605605f3b44b1ecfd by Abseil Team <absl-team@google.com>: Do not directly use __SIZEOF_INT128__. In order to avoid linker errors when building with clang-cl (__fixunsdfti, __udivti3 and __fixunssfti are undefined), this CL uses ABSL_HAVE_INTRINSIC_INT128 which is not defined for clang-cl. PiperOrigin-RevId: 254250739 -- 89ab385cd26b34d64130bce856253aaba96d2345 by Andy Soffer <asoffer@google.com>: Internal changes PiperOrigin-RevId: 254242321 -- cffc793d93eca6d6bdf7de733847b6ab4a255ae9 by CJ Johnson <johnsoncj@google.com>: Adds benchmark for InlinedVector::reserve(size_type) PiperOrigin-RevId: 254199226 -- c90c7a9fa3c8f0c9d5114036979548b055ea2f2a by Gennadiy Rozental <rogeeff@google.com>: Import of CCTZ from GitHub. PiperOrigin-RevId: 254072387 -- c4c388beae016c9570ab54ffa1d52660e4a85b7b by Laramie Leavitt <lar@google.com>: Internal cleanup. PiperOrigin-RevId: 254062381 -- d3c992e221cc74e5372d0c8fa410170b6a43c062 by Tom Manshreck <shreck@google.com>: Update distributions.h to Abseil standards PiperOrigin-RevId: 254054946 -- d15ad0035c34ef11b14fadc5a4a2d3ec415f5518 by CJ Johnson <johnsoncj@google.com>: Removes functions with only one caller from the implementation details of InlinedVector by manually inlining the definitions PiperOrigin-RevId: 254005427 -- 2f37e807efc3a8ef1f4b539bdd379917d4151520 by Andy Soffer <asoffer@google.com>: Initial release of Abseil Random PiperOrigin-RevId: 253999861 -- 24ed1694b6430791d781ed533a8f8ccf6cac5856 by CJ Johnson <johnsoncj@google.com>: Updates the definition of InlinedVector::assign(...)/InlinedVector::operator=(...) to new, exception-safe implementations with exception safety tests to boot PiperOrigin-RevId: 253993691 -- 5613d95f5a7e34a535cfaeadce801441e990843e by CJ Johnson <johnsoncj@google.com>: Adds benchmarks for InlinedVector::shrink_to_fit() PiperOrigin-RevId: 253989647 -- 2a96ddfdac40bbb8cb6a7f1aeab90917067c6e63 by Abseil Team <absl-team@google.com>: Initial release of Abseil Random PiperOrigin-RevId: 253927497 -- bf1aff8fc9ffa921ad74643e9525ecf25b0d8dc1 by Andy Soffer <asoffer@google.com>: Initial release of Abseil Random PiperOrigin-RevId: 253920512 -- bfc03f4a3dcda3cf3a4b84bdb84cda24e3394f41 by Laramie Leavitt <lar@google.com>: Internal change. PiperOrigin-RevId: 253886486 -- 05036cfcc078ca7c5f581a00dfb0daed568cbb69 by Eric Fiselier <ericwf@google.com>: Don't include `winsock2.h` because it drags in `windows.h` and friends, and they define awful macros like OPAQUE, ERROR, and more. This has the potential to break abseil users. Instead we only forward declare `timeval` and require Windows users include `winsock2.h` themselves. This is both inconsistent and poor QoI, but so including 'windows.h' is bad too. PiperOrigin-RevId: 253852615 GitOrigin-RevId: 7a6ff16a85beb730c172d5d25cf1b5e1be885c56 Change-Id: Icd6aff87da26f29ec8915da856f051129987cef6
2019-06-21 22:11:42 +02:00
// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Generates gaussian_distribution.cc
//
// $ blaze run :gaussian_distribution_gentables > gaussian_distribution.cc
//
#include "absl/random/gaussian_distribution.h"
#include <cmath>
#include <cstddef>
#include <iostream>
#include <limits>
#include <string>
#include "absl/base/macros.h"
namespace absl {
namespace random_internal {
namespace {
template <typename T, size_t N>
void FormatArrayContents(std::ostream* os, T (&data)[N]) {
if (!std::numeric_limits<T>::is_exact) {
// Note: T is either an integer or a float.
// float requires higher precision to ensure that values are
// reproduced exactly.
// Trivia: C99 has hexadecimal floating point literals, but C++11 does not.
// Using them would remove all concern of precision loss.
os->precision(std::numeric_limits<T>::max_digits10 + 2);
}
*os << " {";
std::string separator = "";
for (size_t i = 0; i < N; ++i) {
*os << separator << data[i];
if ((i + 1) % 3 != 0) {
separator = ", ";
} else {
separator = ",\n ";
}
}
*os << "}";
}
} // namespace
class TableGenerator : public gaussian_distribution_base {
public:
TableGenerator();
void Print(std::ostream* os);
using gaussian_distribution_base::kMask;
using gaussian_distribution_base::kR;
using gaussian_distribution_base::kV;
private:
Tables tables_;
};
// Ziggurat gaussian initialization. For an explanation of the algorithm, see
// the Marsaglia paper, "The Ziggurat Method for Generating Random Variables".
// http://www.jstatsoft.org/v05/i08/
//
// Further details are available in the Doornik paper
// https://www.doornik.com/research/ziggurat.pdf
//
TableGenerator::TableGenerator() {
// The constants here should match the values in gaussian_distribution.h
static constexpr int kC = kMask + 1;
static_assert((ABSL_ARRAYSIZE(tables_.x) == kC + 1),
"xArray must be length kMask + 2");
static_assert((ABSL_ARRAYSIZE(tables_.x) == ABSL_ARRAYSIZE(tables_.f)),
"fx and x arrays must be identical length");
auto f = [](double x) { return std::exp(-0.5 * x * x); };
auto f_inv = [](double x) { return std::sqrt(-2.0 * std::log(x)); };
tables_.x[0] = kV / f(kR);
tables_.f[0] = f(tables_.x[0]);
tables_.x[1] = kR;
tables_.f[1] = f(tables_.x[1]);
tables_.x[kC] = 0.0;
tables_.f[kC] = f(tables_.x[kC]); // 1.0
for (int i = 2; i < kC; i++) {
double v = (kV / tables_.x[i - 1]) + tables_.f[i - 1];
tables_.x[i] = f_inv(v);
tables_.f[i] = v;
}
}
void TableGenerator::Print(std::ostream* os) {
*os << "// BEGIN GENERATED CODE; DO NOT EDIT\n"
"// clang-format off\n"
"\n"
"#include \"absl/random/gaussian_distribution.h\"\n"
"\n"
"namespace absl {\n"
"namespace random_internal {\n"
"\n"
"const gaussian_distribution_base::Tables\n"
" gaussian_distribution_base::zg_ = {\n";
FormatArrayContents(os, tables_.x);
*os << ",\n";
FormatArrayContents(os, tables_.f);
*os << "};\n"
"\n"
"} // namespace random_internal\n"
"} // namespace absl\n"
"\n"
"// clang-format on\n"
"// END GENERATED CODE";
*os << std::endl;
}
} // namespace random_internal
} // namespace absl
int main(int, char**) {
std::cerr << "\nCopy the output to gaussian_distribution.cc" << std::endl;
absl::random_internal::TableGenerator generator;
generator.Print(&std::cout);
return 0;
}