c ++-default_random_engine始终创建相同系列的数字 [英] c++-default_random_engine creates all the time same series of numbers

问题描述

我正在使用神经网络，所以我想随机创建权重.因此，如果我创建30个神经网络，那么每个神经网络最终都具有相同的权重(假定是随机的)，因此当我给它们提供相同的输入时，输出应该是相同的，否则就不会输出.有帮助吗?

I am working with neural networks, and I want to create the weights randomly. SO if I create 30 Neural networks every single one of them ends up having the same weights(supposed to be random) so when i give them all the same input the output is the same, when it shouldn't. Any help?

这是主要功能

int main(){
std::vector<Improved_NN> v;
std::random_device rd;
std::default_random_engine generator(rd());
std::uniform_real_distribution<double> distribution(-1.0,1.0);
for(int i = 0; i < 30; i++)
{
    Improved_NN temp;
    temp.initialize_weights(generator, distribution);
    v.push_back(temp);
}

Board temp;

for(int i = 0; i < 30; i++)
{
    std::cout <<"\n" << v[i].executeFromExternal(temp);
}

而initialize_weights在这里:

And the initialize_weights is here:

 void Improved_NN::initialize_weights(std::default_random_engine gen,std::uniform_real_distribution<double> dist){
int k,v = 0;
for(k = 0;k<NUM_HIDDEN_1;k++){
    for(v = 0 ; v < NUM_INPUTS; v++){
        mlp_t.w_h1_i[k][v]=dist(gen);
        //std::cout<<mlp_t.w_h1_i[k][v]<<std::endl;
    }
}
for(k = 0;k<NUM_HIDDEN_2;k++){
    for(v = 0 ; v < NUM_HIDDEN_1; v++){
        mlp_t.w_h2_h1[k][v]=dist(gen);
        //std::cout<<mlp_t.w_h2_h1[k][v]<<std::endl;
    }
}
for(k = 0;k<NUM_HIDDEN_3;k++){
    for(v = 0 ; v < NUM_HIDDEN_2; v++){
        mlp_t.w_h3_h2[k][v]=dist(gen);
        //std::cout<<mlp_t.w_h3_h2[k][v]<<std::endl;
    }
}
    for (int a = 0 ; a < NUM_HIDDEN_3;a++){
        mlp_t.w_o_h[0][a] = dist(gen);
        //std::cout<<mlp_t.w_o_h[0][a]<<std::endl;
    }
}

这是我每次执行时得到的输出.

This is the output i get every time i execute.

0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458

0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458 0.521458

非常感谢您.

推荐答案

好了，就像普通的rand()一样，您需要为生成器提供初始种子，该种子必须具有不同的值，以便生成器生成不同的序列:

Well, as with plain old rand() you need to provide initial seed for the generator which needs to be different value in order for generator to generate different sequence:

    std::random_device rd;
    std::default_random_engine generator(rd());

此外，正如user3018144所指出的，请使用单个生成器，而不要使用30个不同的生成器:

Also, as user3018144 pointed out, use single generator, instead of 30 different:

int main(){
    std::vector<Improved_NN> v;
    std::random_device rd;
    std::default_random_engine generator(rd());
    std::uniform_real_distribution<double> distribution(-1.0,1.0);

    for(int i = 0; i < 30; i++)
    {
        Improved_NN temp;

        /*Problem is here*/
        temp.initialize_weights(generator, distribution);
        v.push_back(temp);
    }

    Board temp;

    for(int i = 0; i < 30; i++)
    {
        std::cout <<"\n" << v[i].executeFromExternal(temp);
    }


//for the number of generations, do this....
}

另外，就在这里:

 void Improved_NN::initialize_weights(std::default_random_engine gen,std::uniform_real_distribution<double> dist){

您正在按值传递生成器，这将创建现有生成器的副本.而是通过引用传递:

you're passing the generators by value, which will create a copy of the existing generator. Pass by reference instead:

 void Improved_NN::initialize_weights(std::default_random_engine& gen, std::uniform_real_distribution<double>& dist){

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