在C中为大程序分配内存

Question

The problem is that the .exe file stops if the input file of at least 20 lines; When I exclude the 4 big for loops that contain operations with the following matrices:

int rounded_marks[42][100];
int reassessed[22][k];
int averagecounter[14][k];

...program works fine. Termination of .exe comes when I these big loops are added (I tired to unite them together, but then there will be extremely big loop, and the same .exe termination).

Total number of lines of each for loop is almost 300 in the code.

Can you please check whether the memory allocated is enough for doing operations?

Should I allocate memory for the matrices? How should it look like?

Thank You for the attention.

PS I can't debug, no software available on the PC's (installation prohibited):(

input.dat is multiline csv file.

Here is the .c code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <math.h>

int main(void)

    {
    int lines_allocated = 100;
    int max_line_len = 150;
    double c[42][1000]={0};
    int print;

    char **words = (char **)malloc(sizeof(char*)*lines_allocated);
    if (words==NULL)
        {
        fprintf(stderr,"Out of memory (1).\n");
        exit(1);
        }

    FILE *fp = fopen("input.dat", "r");
    if (fp == NULL)
        {
        fprintf(stderr,"Error opening file.\n");
        exit(2);
        }

    int i;
    for (i=0;1;i++)
        {
        int j;

        if (i >= lines_allocated)
            {
            int new_size;

            new_size = lines_allocated*2;
            words = (char **)realloc(words,sizeof(char*)*new_size);
            if (words==NULL)
                {
                fprintf(stderr,"Out of memory.\n");
                exit(3);
                }
            lines_allocated = new_size;
            }
        words[i] = malloc(max_line_len*sizeof(*(words[i])));
        if (words[i]==NULL)
            {
            fprintf(stderr,"Out of memory (3).\n");
            exit(4);
            }
        if (fgets(words[i],max_line_len-1,fp)==NULL)
            break;

        for (j=strlen(words[i])-1;j>=0 && (words[i][j]=='\n' || words[i][j]=='\r');j--)

        words[i][j]='\0';
        }

    int j;
    int k=i; // k is number of lines
    for(j = 0; j < k; j++)
    {

        char *pptr = words[j];
        int l;
        for (l = 0; l < 42; l++)
        {
            char *ptr = strchr(pptr, ',');
            if (ptr) 
            {
                *ptr = 0;
                c[l][j] = atof(pptr);
                pptr = ptr + 1;
            }
            else if (isdigit(*pptr)) 
            {
                c[l][j] = atof(pptr);
            }
        }    
    }

    int rounded_marks[42][100];
    int averagecounter[14][k];
    int reassessed[22][k];
    for (j=0;j<k;j++)
    {
             //doing some complicated operations for 1st time
    }
    for (j=0;j<k;j++)
    {
             //doing some complicated operations for 2nd time
    }
    for (j=0;j<k;j++)
    {
             //doing some complicated operations for 3rd time
    }
    for (j=0;j<k;j++)
    {
             //doing some complicated operations for 4th time
    }
}

Answer 1

Most implementations have a relatively small limit on the size of a stack frame, so you should not try to allocate large arrays as local variables. However, static arrays and the heap can be very large. So move your declaration of c out of main and make it a global static variable.

In the case of variables whose sizes are determined at run time, like the arrays dependent on k , you should allocate the on the heap using malloc() .

Answer 2

I am more of an ObjC kinda guy, but the first loop :

for (i=0;1;i++)

Isn't that going to be running forever (since 1 is always true) and eventually run out of memory because the first loop allocates memory?