C code to multiply 2 million-digit numbers

MultiplyMillion-Memory.c

//
//  main.c
//  MultiplyX
//
//  Created by Pratik Anand on 02/12/13.
//  Copyright (c) 2013 Pratik Anand. All rights reserved.
//


#include <stdio.h>
#include <stdlib.h>


#define SIZE 100000000


int main(int argc, const char * argv[])
{
    struct timeval tv_start,tv_end;
    
    // insert code here...
    printf("Hello, World!\n");
    
   
    int lookup[10][10];
    //lookup table
    for(int l1=0;l1<=9;l1++)
        for (int l2=0; l2<=9; l2++) {
            lookup[l1][l2]=l1*l2;
        }
    
    
    char *dSum=(char*)malloc(SIZE*sizeof(char));
    for (int dd=0; dd<SIZE; dd++) {
        dSum[dd]='0';
    }
    
  
    
    
    
    const int nsize=1000000;
    
    printf("\nnumber:\n");
    char number[nsize+1];
    for (int k=0; k<nsize; k++) {
        number[k]=rand()%10+'0';
        printf("%c",number[k]);
    }
    
    printf("\nmultiplier:\n");
    
    const int msize=1000000;
    char multiplier[msize+1];
    for (int k=0; k<msize; k++) {
        multiplier[k]=rand()%10+'0';
        printf("%c",multiplier[k]);
    }
    printf("\n");
    char *result=(char*)malloc(SIZE*sizeof(char));
    
    
    int ctrResJ=0;
   
    
    
    
    
    int carry=0;
    int res=0;
    
    int d1=0,d2=0;
    
    int dCarry=0;
    int digit=0;
    
    int dTemp=0;
    int dRes=0;
    int realCtr=0;
    
    
    
    gettimeofday(&tv_start,NULL);
    //tv_start.tv_sec ;// seconds
    //tv_start.tv_usec; // microseconds
    
    
    for (int ctr=msize-1; ctr>=0; ctr--,realCtr++) {
        for (int ctrNum=nsize-1;ctrNum>=0 ; ctrNum--) {
            

            
            res=(number[ctrNum]-'0')*(multiplier[ctr]-'0');
            //res=lookup[number[ctrNum]-'0'][multiplier[ctr]-'0'];
            
            //adding the carry
            res=res+carry;
            
            carry=res/10;
            res=res%10;
            
            //printf("RESULT %c * %c = %d CARRY=%d\n",number[ctrNum],multiplier[ctr],res,carry );
            
            result[ctrResJ++]=res+'0';
            res=0;
            
        }
        
        if(carry>0){
            result[ctrResJ++]=carry+'0';  //last carry
            carry=0;
        }
        
        result[ctrResJ++]='\0';
        
        ctrResJ=0;
        
        
        //add
        
        d2=0;
        
            while (result[d2]!='\0') {
                digit=result[d2]-'0';
                
                dTemp=dSum[d2+realCtr]-'0';
                dRes=(dTemp+digit+dCarry);
                dSum[d2+realCtr]=(dRes%10)+'0';
                dCarry=dRes/10;
                d2++;
            }
            
            if(dCarry>0){
                dSum[d2+realCtr]=dCarry+'0';  //last carry
                dCarry=0;
                d2++;
            }
            //copying for knowing the final end
            d1=d2+realCtr;
            
            d2=0;
            
            //printf("Result is %s\n",dSum);
        
         printf("\nMultiplier digit pos: %d\n",ctr);
        
        
    }
   
    
    
    
    dSum[d1]='\0';
    
    
    
    gettimeofday(&tv_end,NULL);
    printf("\nTime taken :%ld sec\n",tv_end.tv_sec-tv_start.tv_sec);
    printf("\nTime taken :%d us\n",tv_end.tv_usec-tv_start.tv_usec);
    
    
    int i=d1-1;
    char printDigit=0;
    while (i>=0) {
        printDigit=dSum[i];
        printf("%c",printDigit);
        i--;
    }
    printf("\n");
    
    
    free(dSum);
    free(result);
    
    
    return 0;
}