Garbage storage, programming in C - c

Question

I'm new programing in C. I have a main code with 781 lines that is out of control because garbage value is stored in vectors. A short part of the main code is shown below where it calls a subroutine called diff_conv_intermedia1.
diff_conv_intermedia1(&factorteta,&N,ID,DIFF,X1_intermedia,Y1_intermedia,X1C_intermedia,Y1C_intermedia,CU1_intermedia,CV1_intermedia,AW1_intermedia,AE1_intermedia,AS1_intermedia,AN1_intermedia,AP1_intermedia,Q1_intermedia,FXI1,FYI1,FI_intermedia1,1,2,1,1);
int q,w;
for(q=1;q<(*factorteta_Ptr)*2+1;q++)
{
for(w=1;w<(*N_Ptr)+1;w++)
{
printf("%lf\n",AP1_intermedia[q][w]);
}
}
So the subroutine shown below. When I print the results inside the subroutine, everything is OK, but when I print the results outside the subroutine, in the main code, garbage is stored in the vectors as AP1_intermedia. I don't know what could be wrong. I repeat the same procedure with other subroutines and I don't have any errors.
int diff_conv_intermedia1(int *factorteta_Ptr,
int *N_Ptr,
int ID,
double DIFF,
double X[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double Y[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double XC[(*factorteta_Ptr)*2+2][*N_Ptr+2],
double YC[(*factorteta_Ptr)*2+2][*N_Ptr+2],
double CU[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double CV[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double AW[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double AE[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double AS[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double AN[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double AP[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double Q[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double FX[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double FY[(*factorteta_Ptr)*2+1][*N_Ptr+1],
double FI[(*factorteta_Ptr)*2+1][*N_Ptr+1],
int WBC,int EBC,int SBC,int NBC)
{
int i,j;
double value,* valuePtr;
double AED, AWD, AND, ASD;
double AEC, AWC, ANC, ASC;
valuePtr = &value;
// Diffusive coefficients
for(i=1;i<(*factorteta_Ptr)*2+1;i++)
{
for(j=1;j<*N_Ptr+1;j++)
{
AWD = -DIFF*(Y[i][j-1]-Y[i-1][j-1])/(XC[i][j]-XC[i][j-1]);
AED = -DIFF*(Y[i][j]-Y[i-1][j])/(XC[i][j+1]-XC[i][j]);
AND = -DIFF*(X[i][j]-X[i][j-1])/(YC[i+1][j]-YC[i][j]);
ASD = -DIFF*(X[i-1][j]-X[i-1][j-1])/(YC[i][j]-YC[i-1][j]);
// Convection term
if(ID==2)
{
max1_or_min2(CU[i][j-1],1,&value);
AWC=-*valuePtr;
max1_or_min2(CU[i][j],2,&value);
AEC=*valuePtr;
max1_or_min2(CV[i-1][j],1,&value);
ASC=-*valuePtr;
max1_or_min2(CV[i][j],2,&value);
ANC=*valuePtr;
}
if(ID==1)
{
AWC =-CU[i][j-1]*(1.0-FX[i][j-1]);
AEC =CU[i][j]*FX[i][j];
ASC =-CV[i-1][j]*(1.0-FY[i-1][j]);
ANC =CV[i][j]*FY[i][j];
}
// Set Coefficients matrix
AW[i][j] = AWD+AWC;
AE[i][j] = AED+AEC;
AS[i][j] = ASD+ASC;
AN[i][j] = AND+ANC;
AP[i][j] = -(AE[i][j]+AW[i][j]+AN[i][j]+AS[i][j]);
Q[i][j] = 0.0;
}
}
// West Boundary - Inlet B.C
for(i=1;i<(*factorteta_Ptr)*2+1;i++)
{
if(WBC==1) Q[i][1] = Q[i][1]-AW[i][1]*FI[i][0];
if(WBC==2) AP[i][1] = AP[i][1] + AW[i][1];
AW[i][1] = 0.0;
// East Boundary - (1)Dirichlet (2)ZERP-GRAD Outflow B.C
if(EBC==1) Q[i][*N_Ptr] = Q[i][*N_Ptr] - AE[i][*N_Ptr]*FI[i][*N_Ptr+1];
if(EBC==2) AP[i][*N_Ptr] = AP[i][*N_Ptr] + AE[i][*N_Ptr];
AE[i][*N_Ptr] = 0.0;
}
// South Boundary - (1)Dirichlet (2)ZERO-GRAD
for(j=1;j<*N_Ptr+1;j++)
{
if(SBC==1) Q[1][j] = Q[1][j] - AS[1][j]*FI[0][j];
if(SBC==2) AP[1][j] = AP[1][j] + AS[1][j];
AS[1][j] = 0.0;
// North Boundary - (1)Dirichlet (2)ZERO-GRAD
if(NBC==1) Q[(*factorteta_Ptr)*2][j] = Q[(*factorteta_Ptr)*2][j] - AN[(*factorteta_Ptr)*2][j]*FI[(*factorteta_Ptr)*2+1][j];
if(NBC==2) AP[(*factorteta_Ptr)*2][j] = AP[(*factorteta_Ptr)*2][j] + AN[(*factorteta_Ptr)*2][j];
AN[(*factorteta_Ptr)*2][j] = 0.0;
}
// Print
int l,k;
for(l=1;l<(*factorteta_Ptr)*2+1;l++)
{
for(k=1;k<*N_Ptr+1;k++)
{
printf("%lf %lf %lf %lf\n",AP[l][k],AS[l][k],AN[l][k],FI[l][k]);
}
}
return 0;
}
If anybody wants I can send all code, but have many extensions.

Answer 1

In your function declaration:
double AP[(*factorteta_Ptr)*2+1][*N_Ptr+1]
I don't quite think this is doing what you think it is doing. While I haven't seen something like this myself before, I believe that this is telling the compiler to create a variable length 2D array for you based on the other given parameters. Then, you fill in these values in your function. But, because you don't return this value nor do you declare it as pass by reference, it is thrown away when you return, thus the work is lost and you have garbage in your array in main(). Better form would be to create this array in main(), then pass it in by reference something like double *AP[][], or return this array upon exit, or hack things up even worse than this function and just make it a global so that you can see it anywhere.