62 lines
2.1 KiB
C++
62 lines
2.1 KiB
C++
/*
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VIM: let b:cf5build="clang -std=c++20 -O2 -pthread -lstdc++ -I. {SRC} -o {OUT}"
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VIM: let b:cf5run="{OUT}"
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*/
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#include <iostream>
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#include <exception>
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#include <chrono>
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/* This is from "The C++ Programming Language, Fourth Edition
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* by Bjarne Stroustrup"*/
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constexpr int sqrt2(int x, int i = 3, int i_sq = 1){
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return i_sq <= x ? sqrt2(x, i+2, i_sq + i) : i/2-1;
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}
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/* My simplified version:
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* Basically sum(1+2*i) where i==0..n-1 == n^2
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*/
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constexpr int sqrt(int x, int i = 1, int i_sq = 1){
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return i_sq <= x ? sqrt(x, i+1, i_sq + (1+2*i)) : i-1;
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}
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int main ( void )
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{try{
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auto begin = std::chrono::high_resolution_clock::now();
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std::cout << "sqrt(-1)=" << sqrt(-1) << " vs " << sqrt2(-1) << std::endl;
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std::cout << "sqrt(0)=" << sqrt(0) << " vs " << sqrt2(0) << std::endl;
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std::cout << "sqrt(1)=" << sqrt(1) << " vs " << sqrt2(1) << std::endl;
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std::cout << "sqrt(2)=" << sqrt(2) << " vs " << sqrt2(2) << std::endl;
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std::cout << "sqrt(3)=" << sqrt(3) << " vs " << sqrt2(3) << std::endl;
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std::cout << "sqrt(4)=" << sqrt(4) << " vs " << sqrt2(4) << std::endl;
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std::cout << "sqrt(5)=" << sqrt(5) << " vs " << sqrt2(5) << std::endl;
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std::cout << "sqrt(6)=" << sqrt(6) << " vs " << sqrt2(6) << std::endl;
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std::cout << "sqrt(9)=" << sqrt(9) << " vs " << sqrt2(9) << std::endl;
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std::cout << "sqrt(16)=" << sqrt(16) << " vs " << sqrt2(16) << std::endl;
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std::cout << "sqrt(24)=" << sqrt(24) << " vs " << sqrt2(24) << std::endl;
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std::cout << "sqrt(25)=" << sqrt(25) << " vs " << sqrt2(25) << std::endl;
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std::cout << "sqrt(26)=" << sqrt(26) << " vs " << sqrt2(26) << std::endl;
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std::cout << "sqrt(36)=" << sqrt(36) << " vs " << sqrt2(36) << std::endl;
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//......
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auto end = std::chrono::high_resolution_clock::now();
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std::chrono::duration<double> seconds = end - begin;
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std::cout << "Time: " << seconds.count() << std::endl;
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return 0;
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}
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catch ( const std::exception& e )
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{
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std::cerr << std::endl
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<< "std::exception(\"" << e.what() << "\")." << std::endl;
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return 2;
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}
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catch ( ... )
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{
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std::cerr << std::endl
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<< "unknown exception." << std::endl;
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return 1;
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}}
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