print ut my results

This is a discussion on print ut my results within the C Programming forums, part of the General Programming Boards category; Hi pals, My problem is I cant print out my results, I tried a lot of things but unfortunately I ...

  1. #1
    Registered User
    Join Date
    Mar 2009
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    print ut my results

    Hi pals,
    My problem is I cant print out my results, I tried a lot of things but unfortunately I didn't get help me please
    follow my code
    Code:
    /*Laplace equation 2D*/
    /*Build the Mesh*/
    #include<stdio.h>
    #include<stdlib.h>
    #include<math.h>
    #define max 100
    /*====================================================================
                       Defining function VOID
    ======================================================================*/
    /*====================================================================
                         Function Contour
    ======================================================================*/
        void contour(float f[max][max],float x[max],float y[max],int jmax, int imax, float ui,
    	 int i, int j, float il,float it)
    	{
    		
    	for(j=1;j<=jmax;j++)
    	{
    		f[1][j]=ui*x[1];
    		f[imax][j]=ui*x[imax];
    	}
    	for(i=1;i<=imax;i++)
    	{
    		f[i][jmax]=ui*x[i];
    		if((i>=il) && (i<=it))
    		f[i][1]=f[i][2]-0.05*(y[2]-y[1])*(1.0-2*x[i]);
    		else
    		f[i][1]=f[i][2];
    	}
    	}// end contour ()
    /*===================================================================
                             end VOID
    =====================================================================*/
    /*====================================================================
                          Function Res
    ======================================================================*/
    void resi(float res[max][max],float x[max],float y[max],float f[max][max],int i, int j,
    int imax, int jmax, float remax)	
    {
    	for (i=2;i<=imax-1;i++)
    	{
    		for(j=2;j<=jmax-1;j++)
    		res[i][j]=(2/(x[i+1]-x[i-1]))*((f[i+1][j]-f[i][j])/(x[i+1]-x[i])-(f[i][j]-f[i-1][j])/(x[i]-x[i-1]))
    		+(2/(y[j+1]-y[j-1]))*((f[i][j+1]-f[i][j])/(y[j+1]-y[j])-(f[i][j]-f[i][j-1])/(y[j]-y[j-1]));
    	}
    	remax=0;
    	for(i=2;i<=imax-1;i++)
    	{
    		for(j=2;j<=jmax-1;j++)
    		if (fabs(res[i][j])>=remax)
    		remax=abs(res[i][j]);
    	}
    }
    /*================================================================
                              End resi
    ==================================================================*/
    
    
    int 
    main()
    {
    	FILE *mesh;
    	float dx,x[max],y[max],f[max][max],u[max][max],v[max][max],c[max][max],df[max][max],res[max][max];
    	float ys,xs,il,it,ui,dy,remax;
    	
    	int imax,jmax,nmax,n,i,j,s;
    	mesh=fopen("mesh.data","w");
    	
    	il=11;
    	it=31;
    	imax=41;
    	jmax=12;
    	ys=1.24;
    	xs=1.24;
    	ui=1.0;
    	nmax=10000;
    	/*=========================================================
    	               Generating the Mesh
    	===========================================================*/
    	dx=-1.0/(il-it);
    	
    	for (i=il;i<=it;i++)
    	{
    		x[i]=(i-il)*dx;
    		
    	}
    	for (i=it+1;i<=imax;i++)
    	{
    		x[i]=x[i-1]+(x[i-1]-x[i-2])*xs;
    		
    	}
    	for(i=il-1;i>=1;i--)
    	{
    	    x[i]=x[i+1]+(x[i+1]-x[i+2])*xs;
    	    
    	}
    	y[1]=-dx/2;
    	y[2]=dx/2;
    	for(j=3;j<=jmax;j++)
    	{
    	    y[j]=y[j-1]+(y[j-1]-y[j-2])*ys;
    	}
    	/*===============================================================*/
    
    	/*===============================================================
    	                   Initial Conditions
    	=================================================================*/
    	for(i=1;i<=imax;i++)
    	{
    		for(j=1;j<=jmax;j++)
    		f[i][j]=ui*x[i];
    		
    		
    	}
    	/*============================================================*/
    	
    	for(n=1;n<=nmax;n++)
    	{
            contour( f, x, y,jmax,imax, ui,i, j, il,it);
    		resi( res,x,y,f,i,j,imax,jmax,remax);
       
       for(i=2;i<=imax-1;i++)
       {
       	for(j=2;j<=jmax-1;j++)
       	dx=(x[i+1]-x[i-1])/2;
       	dy=(y[j+1]-y[j-1])/2;
       	df[i][j]=-res[i][j]/(-2/(dx*dx)-2/(dy*dy));
       }
       for(i=2;i<=imax-1;i++)
       {
       	for(j=2;j<=jmax-1;j++)
       	f[i][j]=f[i][j]+df[i][j];
       }
       
    	}	
    	
    	
    	/*=============================================================*/
    	/*===============================================================
    	                Calculus of Velocities
    	=================================================================*/
    	for(i=2;i<=imax-1;i++)
    	{
    		for(j=2;j<=jmax-1;j++)
    		u[i][j]=(f[i+1][j]-f[i-1][j])/(x[i+1]-x[i-1]);
    		v[i][j]=(f[i][j+1]-f[i][j-1])/(y[j+1]-y[j-1]);
    		c[i][j]=1.0-u[i][j]*u[i][j]+v[i][j]*v[i][j];
    		
    	}  
    	
    	
    	/*===============================================================
                       	Print the Results
    	==================================================================*/
    	for(j=1;j<=jmax;j++)
    	{
    		for(i=1;i<=imax;i++)
    		/*fprintf(mesh,"%1.15f  %1.15f\n",u[i][j],v[i][j]);*/
    		printf("%lf\n",u[i][j]);
    		printf("\n");
    	}
    	fclose(mesh);	
    	
    	exit(0);
    }

  2. #2
    Kernel hacker
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    Can you explain exactly what your problem with printing the result is?

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
    Registered User
    Join Date
    Mar 2009
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    Hi, yeah sorry for my bad explanation, well in the section print results i would like to print out the velocities u[i][j] and v[i][j], but I did't get

  4. #4
    Kernel hacker
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    Quote Originally Posted by vikingcarioca View Post
    Hi, yeah sorry for my bad explanation, well in the section print results i would like to print out the velocities u[i][j] and v[i][j], but I did't get
    Didn't get what? What are you seeing, and how is that different from what you exect?

    Also, is "%lf" really the right format specifier?


    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  5. #5
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    well I am seeing the results of u[i][j] as 0's, means is wrong when I print out u[i][j], and i hink format %lf is correct. I am new in C not an expert

  6. #6
    Kernel hacker
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    Seeing as your values are "float", I don't see how "%lf" could possibly be even nearly right - it either is undefined, means long double, or double, depending on which year the printf() code was produced.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  7. #7
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    so what i need is to change float for double is this correct ?

  8. #8
    Making mistakes
    Join Date
    Dec 2008
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    One thing: seeing your code I'd recommend doubles instead of floats. Except you only need 6 decimal digits. But in float one can quickly use some accuracy. It's your decision. If you use floats, change %lf to %f.

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