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https://github.com/fastfloat/fast_float.git
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58798ee81f
Apparently the added constexpr makes gcc's control flow analysis to go deeper. If from_chars returns with error then the out parameter remains uninitialized. As it's undefined behavior to use its value, it's better to just skip the rest of the loop in this case.
108 lines
3.0 KiB
C++
108 lines
3.0 KiB
C++
#include "fast_float/fast_float.h"
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#include <cassert>
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#include <cmath>
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#include <cstdio>
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#include <ios>
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#include <iostream>
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#include <system_error>
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template <typename T> char *to_string(T d, char *buffer) {
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auto written = std::snprintf(buffer, 128, "%.*e",
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64, d);
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return buffer + written;
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}
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static fast_float::value128 g_lehmer64_state;
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/**
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* D. H. Lehmer, Mathematical methods in large-scale computing units.
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* Proceedings of a Second Symposium on Large Scale Digital Calculating
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* Machinery;
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* Annals of the Computation Laboratory, Harvard Univ. 26 (1951), pp. 141-146.
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*
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* P L'Ecuyer, Tables of linear congruential generators of different sizes and
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* good lattice structure. Mathematics of Computation of the American
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* Mathematical
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* Society 68.225 (1999): 249-260.
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*/
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static inline void lehmer64_seed(uint64_t seed) {
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g_lehmer64_state.high = 0;
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g_lehmer64_state.low = seed;
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}
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static inline uint64_t lehmer64() {
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fast_float::value128 v = fast_float::full_multiplication(g_lehmer64_state.low,UINT64_C(0xda942042e4dd58b5));
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v.high += g_lehmer64_state.high * UINT64_C(0xda942042e4dd58b5);
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g_lehmer64_state = v;
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return v.high;
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}
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size_t errors;
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void random_values(size_t N) {
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char buffer[128];
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lehmer64_seed(N);
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for (size_t t = 0; t < N; t++) {
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if ((t % 1048576) == 0) {
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std::cout << ".";
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std::cout.flush();
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}
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uint64_t word = lehmer64();
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double v;
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memcpy(&v, &word, sizeof(v));
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{
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const char *string_end = to_string(v, buffer);
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double result_value;
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auto result = fast_float::from_chars(buffer, string_end, result_value);
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if (result.ec != std::errc()) {
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std::cerr << "parsing error ? " << buffer << std::endl;
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errors++;
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if (errors > 10) {
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abort();
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}
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continue;
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}
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if (std::isnan(v)) {
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if (!std::isnan(result_value)) {
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std::cerr << "not nan" << buffer << std::endl;
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errors++;
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if (errors > 10) {
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abort();
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}
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}
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} else if(copysign(1,result_value) != copysign(1,v)) {
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std::cerr << buffer << std::endl;
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std::cerr << "I got " << std::hexfloat << result_value << " but I was expecting " << v
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<< std::endl;
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abort();
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} else if (result_value != v) {
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std::cerr << "no match ? '" << buffer << "'" << std::endl;
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std::cout << "started with " << std::hexfloat << v << std::endl;
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std::cout << "got back " << std::hexfloat << result_value << std::endl;
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std::cout << std::dec;
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errors++;
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if (errors > 10) {
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abort();
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}
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}
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}
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}
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std::cout << std::endl;
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}
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int main() {
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errors = 0;
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size_t N = size_t(1) << (sizeof(size_t) * 4); // shift: 32 for 64bit, 16 for 32bit
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random_values(N);
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if (errors == 0) {
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std::cout << std::endl;
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std::cout << "all ok" << std::endl;
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return EXIT_SUCCESS;
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}
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std::cerr << std::endl;
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std::cerr << "errors were encountered" << std::endl;
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return EXIT_FAILURE;
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}
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