library/random/splitmix64.hpp

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• Last update: 2023-05-31 10:45:25+08:00
• Include: #include "library/random/splitmix64.hpp"
• Link: http://xoshiro.di.unimi.it/splitmix64.c

Required by

• library/data-structure/pbds.hpp
• Discrete Log (離散對數 $a^x \equiv b \pmod m$) (library/math/discrete-log.hpp)
• Random Graph Generator (library/random/graph-generator.hpp)
• random_t (library/random/random.hpp)

Verified with

• test/data-structure/pbds/yosupo-Associative-Array.test.cpp
• test/data-structure/pbds/yosupo-Static-Range-Frequency.test.cpp
• test/data-structure/pbds/yosupo-Static-Range-Sum.test.cpp
• test/math/discrete-log/yosupo-Discrete-Logarithm.test.cpp
• test/math/xor-basis/unit-test-xor-basis.test.cpp
• test/simd/prefix-sum/unit-test-simd-prefix-sum.test.cpp

Code

#pragma once
#include <chrono>


namespace felix {

namespace internal {

// http://xoshiro.di.unimi.it/splitmix64.c

struct splitmix64_hash {
	static unsigned long long splitmix64(unsigned long long x) {
		x += 0x9e3779b97f4a7c15;
		x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
		x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
		return x ^ (x >> 31);
	}
 
	unsigned long long operator()(unsigned long long x) const {
		static const unsigned long long FIXED_RANDOM = std::chrono::steady_clock::now().time_since_epoch().count();
		return splitmix64(x + FIXED_RANDOM);
	}
};

} // namespace internal


} // namespace felix

#line 2 "library/random/splitmix64.hpp"
#include <chrono>


namespace felix {

namespace internal {

// http://xoshiro.di.unimi.it/splitmix64.c

struct splitmix64_hash {
	static unsigned long long splitmix64(unsigned long long x) {
		x += 0x9e3779b97f4a7c15;
		x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
		x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
		return x ^ (x >> 31);
	}
 
	unsigned long long operator()(unsigned long long x) const {
		static const unsigned long long FIXED_RANDOM = std::chrono::steady_clock::now().time_since_epoch().count();
		return splitmix64(x + FIXED_RANDOM);
	}
};

} // namespace internal


} // namespace felix

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