a numerical method... has some error

[srinath29]

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

float*** ivp(float***,int,int,int,float);
float*** bvp(float***,int,int,int,float);
float*** solve(float***,int,int,int,float,float);
void print_box(float***,int,int,int);
void print(float***,int,int,int);


void main()
{
  float alph,h,l,***grid,***a;
  int i,j,n,p,q,r,tot_len_x,tot_len_y,count=0;
  
  printf("Enter the value of h\n");
  scanf("%f",&h);
  printf("Enter the value of alpha\n");
  scanf("%f",&alph);
  
  printf("Enter the length of the plate\n");
  scanf("%f",&tot_len_x);
  printf("Enter the width of the plate\n");
  scanf("%f",&tot_len_y);
  i=(int)((tot_len_x/h)+0.5);
  j=(int)((tot_len_y/h)+0.5);
  i=4;
  j=4;
  printf("Enter number of time steps\n");
  scanf("%d",&n);
 // printf("*****");
 // printf("aaaaa");
  grid=(float ***)malloc((n+1)*sizeof(float**));
  for(p=0;p<=n;p++)
  {
    grid[p]=(float **)malloc((i+1)*sizeof(float*));
    
  }
// printf("aaaab");
  for(p=0;p<=n;p++)
  {
    for(q=0;q<=i;q++)
    {
    
      grid[p][q]=(float *)malloc((j+1)*sizeof(float));
    }
    count=count+q;
  }
  printf("%d",count);
//  printf("aaaaaaa");
  a=ivp(grid,n,j,i,h);
//  printf("%f",a[0][0][0]);
  print(a,n,j,i);
  grid=bvp(a,n,j,i,h);
  grid=solve(grid,n,j,i,h,alph);
  print_box(grid,n,j,i);

  fflush(stdin);
  getchar();
  
  
}

float*** ivp(float ***a,int n, int j, int i,float h)
{
 int p,q,r;
 
 float pi;
 pi=4.0*atan(1.0);
//printf("Entering ivp");
 for(p=0;p<=n;p++)
 {
   for(q=0;q<=i;q++)
   {
   
     for(r=0;r<=j;r++)
     {
       if(p==0)
       {
      a[p][q][r]= sin(2*pi*q*h)*sin(2*pi*r*h);
      printf("%f",sin(2*pi*q*h)*sin(2*pi*r*h));
       }
     }
     
     
  }
   
   
 }
// printf("Exiting ivp");
 
}

float*** bvp(float ***a,int n, int j, int i,float h)
{
  int p,q,r;
// printf("Entering bvp");
  for(p=0;p<=n;p++)
  {
    for(q=0;q<=i;q++)
    {
      for(r=0;r<=j;r++)
      {
    if(p>0)
    {
      if(q==i||r==j)
      {
        a[p][q][r]=0;
      }
      if(q==0||r==0)
      {
        a[p][q][r]=0;
        
      }
      
    }
      }
    }
  }
// printf("Exiting bvp");
}


float*** solve(float ***a,int n,int j,int i,float h,float alph)
{
  int p,q,r;
 // printf("entering solve");
  
  for(p=0;p<=n;p++)
  {
    for(q=0;q<=i;q++)
    {
      for(r=0;r<=j;r++)
      {
    if(p>0)
    {
      if(q>0&&r>0&&q<i&&r<j)
      {
        a[p][q][r]=(1-4*alph)*a[p-1][q][r]+alph*(a[p-1][q-1][r]+a[p-1][q+1][r]+a[p-1][q][r-1]+a[p-1][q][r+1]);
      }
    }
    
      }
    }
  }
 // printf("Exiting solve");
}

void print_box(float ***a ,int n,int j,int i)
{
  int p,q,r;
  for(p=0;p<=n;p++)
  {
    printf("        ===========\n");
    printf("        ||time=%d||\n",p);
    printf("======================================\n\n\n");
    for(q=i;q>=0;q--)
    {
      
      for(r=j;r>=0;r--)
      {
    printf("\t%f",a[p][q][r]);
      }
      printf("\n");
    }
    printf("======================================\n\n\n");
  }
  
}

void print(float ***a,int n,int j,int i)
{
//  printf("%f",a[0][0][0]);
  int p,q,r;
  for(p=0;p<=n;p++)
  {
    for(q=0;q<=i;q++)
    {
      for(r=0;r<=j;r++)
      {
    printf("U(%d,%d,%d) = %f",q,r,p,a[p][q][r]);
      }
    }
  }
}

I don't know what is the problem! Tried to debug it.. but the array is not getting printed... It's a program for solving heat equation in 2 dimension.

[Malcolm McLean]

I can only imagine that n has not been entered correctly.

You need to test your diagnostic print routines separately, on known grids. If you can't print the results, then there's no way you can tell what the rest of the program is doing.

[dmh2000]

several of your functions are prototyped as returning a value, but they don't. don't even try to run your program when you have significant compiler warnings.
warning C4716: 'solve' : must return a value
warning C4716: 'bvp' : must return a value
warning C4716: 'ivp' : must return a value

[AndiPersti]

Another problem which you would have noticed if you would have read the warnings:

int i,j,n,p,q,r,tot_len_x,tot_len_y,count=0;
  
printf("Enter the length of the plate\n");
scanf("%f",&tot_len_x);
printf("Enter the width of the plate\n");
scanf("%f",&tot_len_y);

Bye, Andreas