将函数传递给结构数组内的指针

Question

我正在尝试使用 C 从头开始实现一个神经网络，但我遇到了一个关于如何为每一层动态分配激活函数的小问题。我创建了以下结构来表示网络的每一层：

typedef struct network{
    char* type;
    double* neurons;
    double (*activation_function)(double);
    double bias;
}network;

所以我有几个功能，例如：

double tanh(double weight);

并像这样创建一个网络阵列

network* neural_network = (network*) malloc(num_layers * sizeof(network));

但如果我这样做

neural_network[i].activation_function = &tanh;

代码编译没有错误，当我运行时给出分段错误。

如果我这样做

neural_network[i] -> activation_function = &tanh;

我得到以下编译错误：

error: invalid type argument of '->' (have 'network' {aka 'struct network'})

有什么解决办法吗？

下面的最小可重现代码：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
#define ALLOW_REALLOC_LAYER 1 // allows a new layer to be added to a neural network where the pre-allocated space is already full


typedef struct network{
    char* type;
    double* neurons;
    double (*activation_function)(double);
    double bias;
}network;

double tanh(double weight){                     //tanh's range is between -1 and 1
    return((pow(M_E, 2 * weight) - 1)/(pow(M_E, 2 * weight) + 1));
}

double sigmoid(double weight){                  // sigmoid's range is between 0 and 1
    return(1/(1 + pow(M_E, weight * (-1))));
}

double identity(double weight){
    return(weight);
}

network* new_network(int num_layers){ // the 1st position of the array is the input layer and the nth position is the output layer
    if(num_layers < 2){
        printf("A neural network needs at least two layers\n");
        return(NULL);
    }

    int i;
    network* neural_network = (network*) malloc(num_layers * sizeof(network)); // initializing the neural network

    for(i = 0; i < num_layers; i++){
        neural_network[i].bias = 0.333; // initializing the bias of each network
        neural_network[i].neurons = NULL;
        neural_network[i].type = "feedforward";
    }

    return(neural_network);
}

void add_layer(network* neural_network, int* num_layers, int num_neurons, char* type, double (function)(double)){
    if(neural_network == NULL){
        printf("Neural network not initialized. Use new_network(int num_layers) to initialize it\n");
        return;
    }

    int i, j;
    pcg32_random_t rng1;

    for(i = 0; i < *num_layers; i++)
        if(neural_network[i].neurons == NULL)
            break;
                                                                                                    // checks if the neural network already has the pre-defined layers allocated
    if(i == *num_layers && ALLOW_REALLOC_LAYER){                                                    // if yes and ALLOW_REALLOC_LAYER == 1, then the neural network can be expanded
        neural_network = (network*) realloc(neural_network, (*num_layers + 1) * sizeof(network));

        neural_network[i].bias = 0.5; 
        neural_network[i].neurons = NULL;
        neural_network[i].type = type;
        neural_network[i].activation_function = &tanh;

        *num_layers = *num_layers + 1;                                                                              
    }else if(i == *num_layers && !ALLOW_REALLOC_LAYER){                                             // if yes and ALLOW_REALLOC_LAYER == 0, an error message is raised
        printf("Pre-allocated space is already full. Set ALLOW_REALLOC_LAYER to 1 to expand the neural network.");
        return;
    }

    neural_network[i].neurons = (double*) malloc(num_neurons * sizeof(double)); // creating the new layer

    for(j = 0; j < num_neurons; j++)                                        
        neural_network[i].neurons[j] = 0.5; // initializing the weights of each neuron

    printf("TEST : weight = %g \ntanh = %g", neural_network[i].neurons[0], neural_network[i].activation_function(neural_network[i].neurons[0]));
    return;
}


int main(void){
    int num_layers = 3;
    network* NN = new_network(num_layers);
    add_layer(NN, &num_layers, 10, "feedforward", &tanh);
    return(0);
}

Answer 1

事实证明这只是函数 add_layer() 的错误条件设置。而不是

if(i == *num_layers && ALLOW_REALLOC_LAYER){                                                    // if yes and ALLOW_REALLOC_LAYER == 1, then the neural network can be expanded
        neural_network = (network*) realloc(neural_network, (*num_layers + 1) * sizeof(network));

        neural_network[i].bias = 0.5; 
        neural_network[i].neurons = NULL;
        neural_network[i].type = type;
        neural_network[i].activation_function = &tanh;

        *num_layers = *num_layers + 1;                                                                              
    }else if(i == *num_layers && !ALLOW_REALLOC_LAYER){                                             // if yes and ALLOW_REALLOC_LAYER == 0, an error message is raised
        printf("Pre-allocated space is already full. Set ALLOW_REALLOC_LAYER to 1 to expand the neural network.");
        return;
    }

应该是

// checks if the neural network already has the pre-defined layers allocated
if(i == *num_layers && !ALLOW_REALLOC_LAYER){                                               // if yes and ALLOW_REALLOC_LAYER == 0, an error message is raised
    printf("Pre-allocated space is already full. Set ALLOW_REALLOC_LAYER to 1 to expand the neural network.");
    return;
}

// if yes and ALLOW_REALLOC_LAYER == 1, then the neural network can be expanded
neural_network = (network*) realloc(neural_network, (*num_layers + 1) * sizeof(network));

neural_network[i].bias = 0.5; 
neural_network[i].neurons = NULL;
neural_network[i].num_neurons = num_neurons;
neural_network[i].type = type;
neural_network[i].activation_function = &tanh;

*num_layers = *num_layers + 1;

谢谢你的帮助，Unn。

将函数传递给结构数组内的指针

Passing a function to a pointer inside a struct array

c

arrays

struct

function-pointers