Sherman-Morrison/tests/cMaponiA3_test_3x3_3.cpp

// main.cpp
#include "Helpers.hpp"
#include "SM_Maponi.hpp"

int main() {

  unsigned int M = 3; // Dimension of the Slater-matrix
  unsigned int i, j;  // Indices for iterators

  // Declare, allocate all vectors and matrices and fill them with zeros
  unsigned int *Ar_index = new unsigned int[M];
  double *A = new double[M * M]; // The matrix to be inverted
  double *A0 =
      new double[M * M]; // A diagonal matrix with the digonal elements of A
  double *Ar = new double[M * M];     // The update matrix
  double *A0_inv = new double[M * M]; // The inverse

  // Fill with zeros
  for (i = 0; i < M; i++) {
    for (j = 0; j < M; j++) {
      A0[i * M + j] = 0;
      Ar[i * M + j] = 0;
      A0_inv[i * M + j] = 0;
    }
  }

  // Initialize A with M=3 and fill acc. to Eq. (17) from paper
  A[0] = 1;
  A[3] = 1;
  A[6] = -1;
  A[1] = 1;
  A[4] = 1;
  A[7] = 0;
  A[2] = -1;
  A[5] = 0;
  A[8] = -1;

  showMatrix(A, M, "A");

  // Initialize the diagonal matrix A0,
  // the inverse of A0_inv of diagonal matrix A0_inv
  // and the update matrix Ar
  for (i = 0; i < M; i++) {
    A0[i * M + i] = A[i * M + i];
    A0_inv[i * M + i] = 1.0 / A[i * M + i];
    Ar_index[i] = i + 1; // ! First column needs to start with 1 !
    for (j = 0; j < M; j++) {
      Ar[i * M + j] = A[i * M + j] - A0[i * M + j];
    }
  }

  // Define pointers dim and n_updates to use in Sherman-Morrison(...) function
  // call
  MaponiA3(A0_inv, M, M, Ar, Ar_index);
  showMatrix(A0_inv, M, "A0_inv");

  // Deallocate all vectors and matrices
  delete[] A, A0, A0_inv, Ar, Ar_index;

  return 0;
}