betti_minimal()

M2_arrayint gbres_comp::betti_minimal

(

)

const

Definition at line 326 of file res-a2.cpp.

{
  int lev, i, d;
  int lo = nodes[0]->output_free_module()->lowest_primary_degree();
  if (n_nodes >= 2)
    {
      int lo1 = nodes[1]->output_free_module()->lowest_primary_degree() - 1;
      if (lo1 < lo) lo = lo1;
    }
  if (n_nodes >= 3)
    {
      int lo2 = nodes[2]->output_free_module()->lowest_primary_degree() - 2;
      if (lo2 < lo) lo = lo2;
    }
  int hi = lo;
  int len = 1;
 
  // Set the hi degree, and len
  for (lev = 0; lev < n_nodes; lev++)
    {
      const FreeModule *F = free_module(lev);
      if (F->rank() > 0) len = lev;
 
      for (i = 0; i < F->rank(); i++)
        {
          d = F->primary_degree(i) - lev;
          if (d > hi) hi = d;
        }
    }
 
  int *bettis;
  betti_init(lo, hi, len, bettis);
 
  for (lev = 0; lev <= len; lev++)
    {
      const FreeModule *F = free_module(lev);
 
      for (i = 0; i < F->rank(); i++)
        {
          d = F->primary_degree(i) - lev - lo;
          bettis[lev + (len + 1) * d]++;
        }
    }
  M2_arrayint result = betti_make(lo, hi, len, bettis);
  freemem(bettis);
  return result;
}

References ResolutionComputation::betti_init(), ResolutionComputation::betti_make(), free_module(), freemem(), n_nodes, nodes, FreeModule::primary_degree(), FreeModule::rank(), and result().

Referenced by get_betti().