-//void Compute_Omega(double* X, int* Y, double* M, int* pn, int* pd, double* W)
-//{
-// int n=*pn, d=*pd;
-// int dim = d + d*d + d*d*d;
-// //double* W = (double*)malloc(dim*dim*sizeof(double));
-//
-// // (Re)Initialize W:
-// for (int j=0; j<dim; j++)
-// {
-// for (int k=0; k<dim; k++)
-// W[j*dim+k] = 0.0;
-// }
-// double* g = (double*)malloc(dim*sizeof(double));
-// for (int i=0; i<n; i++)
-// {
-// // g == gi:
-// for (int j=0; j<d; j++)
-// g[j] = Y[i] * X[mi(i,j,n,d)] - M[j];
-// for (int j=d; j<d+(d*d); j++)
-// {
-// int idx1 = (j-d) % d; //num row
-// int idx2 = ((j-d) - idx1) / d; //num col
-// g[j] = 0.0;
-// if (idx1 == idx2)
-// g[j] -= Y[i];
-// g[j] += Y[i] * X[mi(i,idx1,n,d)]*X[mi(i,idx2,n,d)] - M[j];
-// }
-// for (int j=d+d*d; j<dim; j++)
-// {
-// int idx1 = (j-d-d*d) % d; //num row
-// int idx2 = ((j-d-d*d - idx1) / d) %d; //num col
-// int idx3 = (((j-d-d*d - idx1) / d) - idx2) / d; //num "depth"
-// g[j] = 0.0;
-// if (idx1 == idx2)
-// g[j] -= Y[i] * X[mi(i,idx3,n,d)];
-// if (idx1 == idx3)
-// g[j] -= Y[i] * X[mi(i,idx2,n,d)];
-// if (idx2 == idx3)
-// g[j] -= Y[i] * X[mi(i,idx1,n,d)];
-// g[j] += Y[i] * X[mi(i,idx1,n,d)]*X[mi(i,idx2,n,d)]*X[mi(i,idx3,n,d)] - M[j];
-// }
-// // Add 1/n t(gi) %*% gi to W
-// for (int j=0; j<dim; j++)
-// {
-// for (int k=0; k<dim; k++)
-// W[j*dim+k] += g[j] * g[k] / n;
-// }
-// }
-// free(g);
-//}
-
-// Optimisation attempt: