Error:No matching function for call to - c++

Question

I am very very new to C++ and I am trying to call the function "jacobi" which performs a user specified number of iterations for the jacobi method (or at least I hope so). On the line where I call 'jacobi' I get the error "No matching function to call to "jacobi". I have read other posts similar to this one and have tried to apply it to my own code but I have been unsuccessful. Maybe there are other issues in my code causing this problem. As mentioned I am very new C++ so any help would be appreciated and please break it down for me.
#include <iostream>
using namespace std;
void jacobi (int size, int max, int B[size], int A[size][size], int init[size], int x[size]){
////
//// JACOBI
////
int i,j,k,sum[size];
k = 1;
while (k <= max) // Only continue to max number of iterations
{
for (i = 0; i < size; i++)
{
sum[i] = B[i];
for (j = 0; j < size; j++)
{
if (i != j)
{
sum[i] = sum[i] - A[i][j] * init[j]; // summation
}
}
}
for (i = 0; i < size; i++) ////HERE LIES THE DIFFERENCE BETWEEN Guass-Seidel and Jacobi
{
x[i] = sum[i]/A[i][i]; // divide summation by a[i][i]
init[i] = x[i]; //use new_x(k+1) as init_x(k) for next iteration
}
k++;
}
cout << "Jacobi Approximation to "<<k-1<<" iterations is: \n";
for(i=0;i<size;i++)
{
cout <<x[i]<< "\n"; // print found approximation.
}
cout << "\n";
return;
}
int main (){
// User INPUT
// n: number of equations and unknowns
int n;
cout << "Enter the number of equations: \n";
cin >> n;
// Nmax: max number of iterations
int Nmax;
cout << "Enter max number of interations: \n";
cin >> Nmax;
// int tol;
// cout << "Enter the tolerance level: " ;
// cin >> tol;
// b[n] and a[n][n]: array of coefficients of 'A' and array of int 'b'
int b[n];
int i,j;
cout << "Enter 'b' of Ax = b, separated by a space: \n";
for (i = 0; i < n; i++)
{
cin >> b[i];
}
// user enters coefficients and builds matrix
int a[n][n];
int init_x[n],new_x[n];
cout << "Enter matrix coefficients or 'A' of Ax = b, by row and separate by a space: \n";
for (i = 0; i < n; i++)
{
init_x[i] = 0;
new_x[i] = 0;
for (j = 0; j < n; j++)
{
cin >> a[i][j];
}
}
jacobi (n, Nmax, b, a, init_x, new_x);
}

Answer 1

The problem:
There are several problems, related to the use of arrays:
You can't pass arrays as parameter by value.
You can't pass multidimensional arrays as parameter if the dimensions are variable
You can't define arrays of variable length in C++
Of course there are ways to do all these kind of things, but it uses different principles (dynamic allocation, use of pointers) and requires additional work (especially for the access of multidimensional array elements).
Fortunately, there is a much easier solution also !
The solution:
For this kind of code you should go for vector : these manage variable length and can be passed by value.
For the jacobi() function, all you have to do is to change its definition:
void jacobi(int size, int max, vector<int> B, vector<vector<int>> A, vector<int> init, vector<int> x) {
int i, j, k;
vector<int> sum(size); // vector of 'size' empty elements
// The rest of the function will work unchanged
...
}
Attention however: the vectors can be of variable size and this jacobio implementation assumes that all the vectors are of the expected size. In professional level code you should check that it's the case.
For the implementation of main(), the code is almost unchanged. All you have to do is to replace array definitions by vector definitions:
...
vector<int> b(n); // creates a vector that is initialized with n elements.
...
vector<vector<int>> a(n,vector<int>(n)); // same idea for 2 dimensional vector (i.e. a vector of vectors)
vector<int> init_x(n), new_x(n); // same principle as for b
...