computeResiduals

#include <cmath>

void computeResiduals(int n, double *A, double *b, double *x, double &r1, double &r2) {
    double norm_b = 0.0;
    for (int i = 0; i < n; i++) {
        norm_b += std::fabs(b[i]);
    }

    double norm_residual = 0.0;
    for (int i = 0; i < n; i++) {
        double Ax = 0.0;
        for (int j = 0; j < n; j++) {
            Ax += A[i * n + j] * x[j];
        }
        norm_residual += std::fabs(Ax - b[i]);
    }
    r1 = norm_residual / norm_b;

    double norm_x_hat = 0.0;
    double norm_diff = 0.0;
    for (int i = 0; i < n; i++) {
        double x_hat_i = (i + 1) % 2;
        norm_x_hat += std::fabs(x_hat_i);
        norm_diff += std::fabs(x[i] - x_hat_i);
    }
    r2 = norm_diff / norm_x_hat;
}