Printing same results for all iterations in a loop

[Vigii]

Hi,

Here is my part of my code with issues.

I'm trying to carry forward the results of the previous iteration value to the current iteration. But I cant understand why does it prints same values through all iterations.

Please help me to find where I'm going wrong.

Thanks in Advance

                 int tdms (int m, float* x,float* y,float* z, float* w, float* u,float tt,float ddt )
                 {
                     h[0]=0;g[0]=0;
                     
                             for(int i=1;i<m;i++)           
                             {
                                     h[i]=z[i]/(y[i]-(x[i]*h[i-1]));
                                     g[i]=(w[i]-(x[i]*g[i-1]))/(y[i]-(x[i]*h[i-1]));
                                     //cout<<1<<"\t"<<h[1]<<"\t"<<g[1]<<"\t"<<z[1]<<"\t"<<y[1]<<"\t"<<x[1]<<"\t"<<h[0]<<"\n";
                             }
                     for (int k=1;k<=tt/ddt+1;k++)
                      {
                       cout<<"Time Step:"<<k*ddt<<"Sec\n";
                       std::copy (u,u+m,un);
                             for(int i=(m-1);i>0;i--)
                             {
                                     u[i] =(-h[i]*un[i+1])+g[i];
                                     cout<<i<<"\t"<<u[i]<<"\n";
                       }}
                 }

[ne555]

Use descriptive name variables

¿what's `un'?
¿is `un[m]' valid?
¿why you don't care about `u[0]' ?

> But I cant understand why does it prints same values through all iterations.
¿what is supposed to happen?
Try to make your testcase self-contained so we can actually test it.

[Vigii]

Here is my full code. Please help me.

#include <iostream.h>
#include <conio.h>
#include <algorithm>
#include <fstream>
#include <iomanip>
#include <sstream>
#include <string>
#include <direct.h>

using namespace std;

void print();
void complete();


class explict
{
      private:
              float un[100],h[100],g[100];
              static const string result;
              
      
      public:
            
             int read_data (float &a,float &b, float &c, float &d, float &e, float &f)
                 {
                        print();
                        cout<<"\nThis program computes the velcoity of suddenly accelerated plate \nover a period of time \n";
                        print();
                        cout<<"\nPlease Enter the following details in SI units.....\n\n";
                        cout<<"Distance between the two plates (h)  m   :";cin>>a;
                        cout<<"Velocity of the moving plate    (u0) m/s :";cin>>b;
                        cout<<"Kinematic viscosity of fluid    (v)  m2/s:";cin>>c;
                        print();
                        cout<<"\nSetting the Grid for the problem...\n\nGrid Spacing required along\n1.Y-Direction \t\t\t        (m):";cin>>d;
                        cout<<"2.Time step Interval\t\t\t(m):";cin>>e;
                        cout<<"\nTime step at which velcoity to be found (s):";cin>>f;
                        print();cout<<"\n";
                        
                 }
                 
                 int array (float *uu, int m,float c)
                 {
                         for(int i=0;i<=m-1;i++)
                            {
                                    if(i==m-1) 
                                    {uu[i]=c;}else
                                    {uu[i]=0;}
                                    //cout<<i<<"\t"<<u[i]<<"\n";
                            }
                 }
                 
                 int initialize (int m, float o,float* aa,float* bb,float* cc,float* dd, float* u)
                 {
                     for (int i=1;i<m;i++)
                     {
                         aa[i]=o;
                         bb[i]=-(2*o+1);
                         cc[i]=o;
                         switch (i)
                         {
                                case 1:
                                     dd[i]=-1-(aa[i]*u[i-1]);break;
                                case 39:
                                     dd[i]=-1-(aa[i]*u[i+1]);break;
                                default:
                                     dd[i]=-1;break;
                         }
                         //cout<<i<<"\t"<<aa[i]<<"\t"<<bb[i]<<"\t"<<cc[i]<<"\t"<<dd[i]<<"\n";
                         }
                 }        
                 
                 int tdms (int m, float* x,float* y,float* z, float* w, float* u,float tt,float ddt )
                 {
                    for(int k=1; k<=tt/ddt+1;k++)
                    {
                             std::copy(u,u+m,un);
                    
                             h[0]=0;g[0]=0;
                     
                                 for(int i=1;i<m;i++)           
                                 {
                                         h[i]=z[i]/(y[i]-(x[i]*h[i-1]));
                                         g[i]=(w[i]-(x[i]*g[i-1]))/(y[i]-(x[i]*h[i-1]));   
                                 }
                                 un[m-1]=g[m-1];cout<<m-1<<"\t"<<un[m-1]<<"\n";
                                 for(int i=(m-2);i>0;i--)
                                 {
                                         u[i] =(-h[i]*un[i+1])+g[i];
                                         cout<<i<<"\t"<<u[i]<<"\n";
                                 }//cout<<1<<"\t"<<h[1]<<"\t"<<g[1]<<"\t"<<z[1]<<"\t"<<y[1]<<"\t"<<x[1]<<"\t"<<u[m-2]<<"\t"<<u[m-1]<<"\n";
                     }
                 }
                 
                 
};

int main()
{
    float h,u0,v,dx,dt,t,d,uu[100],aa[100],bb[100],cc[100],dd[100];
    int n,a;
    explict x;
    
    x.read_data(h,u0,v,dx,dt,t);
    
    d=v*(dt/(dx*dx));
    n=(h/dx);                     //cout<<h<<"\t"<<dx<<"\t"<<n<<"\t"<<d<<"\n";
    
    x.array ( uu ,n+1,u0 );
    x.initialize(n,d,aa,bb,cc,dd,uu);
    

    x.tdms(n,aa,bb,cc,dd,uu,t,dt);cout<<"\n";    
    
    
    getch();
}

void print()
{
     cout<<"-----------------------------------------------------------------";
} 

void complete()
{
     cout<<"\nSolution is Obtained\n";
     print();
}

[ne555]

#include <iostream>
You don't seem to use `direct.h' (I don't have it), and I really hate that useless `getch()'

The compiler complains on you saying that you will return a value but you don't do that.


Also, provide an example input, with its correspondent expected output