声明两个大的二维数组给分段错误 [英] Declaring two large 2d arrays gives segmentation fault

问题描述

我试图声明和两个二维数组分配内存。但是试图将值赋给itemFeatureQ时，[39] [16816]我得到一个分段保管库。因为我有2GB的RAM，只使用堆19MB我无法理解这一点。这里是code;

 双** reserveMemory（INT行，诠释列）
{
    双**阵列;
    INT I;
    阵列=（双**）的malloc（行*的sizeof（双*））;
    如果（阵列== NULL）
    {
        fprintf中（标准错误，内存不足的\\ n）;
        返回NULL;
    }
    对于（i = 0; I＆LT;行;我++）
    {
        数组[我] =（双*）malloc的（列* sizeof的（双*））;
        如果（阵列== NULL）
        {
            fprintf中（标准错误，内存不足的\\ n）;
            返回NULL;
        }
    }    返回数组;}无效populateUserFeatureP（双** userFeatureP）
{
    INT X，Y;    为（X = 0; X＆LT;客户; X ++）
    {
        对于（Y = 0; Y＆LT;特点; Y ++）
        {
            userFeatureP [X] [Y] = 0;
        }
    }
}无效populateItemFeatureQ（双** itemFeatureQ）
{
    INT X，Y;    为（X = 0; X＆下;特征; X ++）
    {
        对于（Y = 0; Y＆LT;电影; Y ++）
        {
            的printf（（％D，％D）\\ n，X，Y）;
            itemFeatureQ [X] [Y] = 0;
        }
    }
}INT主（INT ARGC，CHAR *的argv []）{    双** userFeatureP = reserveMemory（480189，40）;
    双** itemFeatureQ = reserveMemory（40，17770）;    populateItemFeatureQ（itemFeatureQ）;
    populateUserFeatureP（userFeatureP）;    返回0;
}
 

解决方案

您有几个错字 - 变化：

 数组[我] =（双*）malloc的（列* sizeof的（双*））;
    如果（阵列== NULL）
 

到

 数组[我] =（双*）malloc的（列*的sizeof（双））;
    如果（阵列[我] == NULL）
 

i'm trying to declare and allocate memory for two 2d-arrays. However when trying to assign values to itemFeatureQ[39][16816] I get a segmentation vault. I can't understand it since I have 2GB of RAM and only using 19MB on the heap. Here is the code;

double** reserveMemory(int rows, int columns)
{
    double **array;
    int i;
    array = (double**) malloc(rows * sizeof(double *));
    if(array == NULL)
    {
        fprintf(stderr, "out of memory\n");
        return NULL;
    }
    for(i = 0; i < rows; i++)
    {
        array[i] = (double*) malloc(columns * sizeof(double *));
        if(array == NULL)
        {
            fprintf(stderr, "out of memory\n");
            return NULL;
        }
    }

    return array;

}

void populateUserFeatureP(double **userFeatureP)
{
    int x,y;

    for(x = 0; x < CUSTOMERS; x++)
    {
        for(y = 0; y < FEATURES; y++)
        {
            userFeatureP[x][y] = 0;
        }
    }
}

void populateItemFeatureQ(double **itemFeatureQ)
{
    int x,y;

    for(x = 0; x < FEATURES; x++)
    {
        for(y = 0; y < MOVIES; y++)
        {
            printf("(%d,%d)\n", x, y);
            itemFeatureQ[x][y] = 0;
        }
    }
}

int main(int argc, char *argv[]){

    double **userFeatureP = reserveMemory(480189, 40);
    double **itemFeatureQ = reserveMemory(40, 17770);

    populateItemFeatureQ(itemFeatureQ);
    populateUserFeatureP(userFeatureP);

    return 0;
}

解决方案

You have a couple of typos - change:

    array[i] = (double*) malloc(columns * sizeof(double *));
    if(array == NULL)

to:

    array[i] = (double*) malloc(columns * sizeof(double));
    if(array[i] == NULL)

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