用1和0創建一個隨機的std :: vector C++

Question

我想創建一個由我設置的比例的隨機1和0的向量（在我稱之爲丟失的程序中）向量的大小與之前相同創建矢量CSUM。

在MATLAB

這將是

dropout=0.9; 
n_elements=size(CSUM) 
drpoutmask = (rand(n_elements) > dropout); 

用C++

我

size_t elements = Csum.size(); 
std::vector<float> y(elements); 
std::uniform_real_distribution<float> distribution(0.0f, 1.0f); 
std::mt19937 engine; // Mersenne twister MT19937 
auto generator = std::bind(distribution, engine); 
std::generate_n(y.begin(), elements, generator); 
std::vector<int> dropoutmask(elements,0); 
float dropout=0.9; 

for(int i=0; i<elements; i++) 
    { 
    if(y.at(i)>dropout) 
    { 
    dropoutmask.at(i)=1; 
    } 
    } 
} 

其作品，但對於巨大的載體是非常非常慢，有沒有更快的方式做到這一點？我在C++上很新。

任何幫助將非常感激

Answer 1

1. 你知道bernoulli distribution，對不對？您可以使用它來直接生成整數向量。
   實施例：

   #include <iostream> 
   #include <algorithm> 
   #include <string> 
   #include <random> 
   
   int main() 
   { 
       constexpr double dropout = 0.9; // Chance of 0 
       constexpr size_t size = 1000; 
       std::random_device rd; 
       std::mt19937 gen(rd()); 
       std::bernoulli_distribution dist(1 - dropout); // bernoulli_distribution takes chance of true n constructor 
   
       std::vector<int> dropoutmask(size); 
       std::generate(dropoutmask.begin(), dropoutmask.end(), [&]{ return dist(gen); }); 
       size_t ones = std::count(dropoutmask.begin(), dropoutmask.end(), 1); 
       std::cout << "vector contains " << ones << " 1's, out of " << size << ". " << ones/double(size) << "%\n"; 
       std::cout << "vector contains " << size - ones << " 0's, out of " << size << ". " << (size - ones)/double(size) << "%\n"; 
   } 
   

   直播例如：http://coliru.stacked-crooked.com/a/a160743185ded5c5

2. 替代地，可以創建具有希望尺寸的整數向量（這將設置爲0的所有元素），設置前N個元素爲1，其中，n是(1 - dropout) * size（你說你想要一個比例，而不是隨機數量接近比例），然後洗牌矢量。

   #include <iostream> 
   #include <algorithm> 
   #include <string> 
   #include <random> 
   
   int main() 
   { 
       constexpr double dropout = 0.9; // Chance of 0 
       constexpr size_t size = 77; 
       std::random_device rd; 
       std::mt19937 gen(rd()); 
   
       std::vector<int> dropoutmask(size); 
       std::fill_n(dropoutmask.begin(), dropoutmask.size() * (1 - dropout), 1); 
       std::shuffle(dropoutmask.begin(), dropoutmask.end(), gen); 
   
       size_t ones = std::count(dropoutmask.begin(), dropoutmask.end(), 1); 
       std::cout << "vector contains " << ones << " 1's, out of " << size << ". " << ones/double(size) << "%\n"; 
       std::cout << "vector contains " << size - ones << " 0's, out of " << size << ". " << (size - ones)/double(size) << "%\n"; 
   
       for (auto i :dropoutmask) { 
        std::cout << i << ' '; 
       } 
       std::cout << '\n'; 
   } 
   

活生生的例子：http://coliru.stacked-crooked.com/a/0a9dacd7629e1605