stress_model.c

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#include <sfdpgen/post_process.h>
#include <sfdpgen/spring_electrical.h>
#include <sfdpgen/stress_model.h>
#include <sparse/SparseMatrix.h>
#include <sparse/general.h>
#include <stdbool.h>
 
int stress_model(int dim, SparseMatrix B, double *x, int maxit_sm) {
  SparseMatrix A = B;
  int rc = 0;
 
  if (!SparseMatrix_is_symmetric(A, false) || A->type != MATRIX_TYPE_REAL) {
    if (A->type == MATRIX_TYPE_REAL) {
      A = SparseMatrix_symmetrize(A, false);
      A = SparseMatrix_remove_diagonal(A);
    } else {
      A = SparseMatrix_get_real_adjacency_matrix_symmetrized(A);
    }
  }
  A = SparseMatrix_remove_diagonal(A);
 
  const int m = A->m;
 
  SparseStressMajorizationSmoother sm = SparseStressMajorizationSmoother_new(
      A, dim, x); // weight the long distances
 
  if (!sm) {
    rc = -1;
    goto RETURN;
  }
 
  sm->tol_cg = 0.1; /* we found that there is no need to solve the Laplacian
                       accurately */
  sm->scheme = SM_SCHEME_STRESS;
  SparseStressMajorizationSmoother_smooth(sm, dim, x, maxit_sm);
  for (int i = 0; i < dim * m; i++) {
    x[i] /= sm->scaling;
  }
  SparseStressMajorizationSmoother_delete(sm);
 
RETURN:
  if (A != B)
    SparseMatrix_delete(A);
  return rc;
}