pfaff.hpp

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// Copyright 1996 Michael E. Stillman.
 
#ifndef _pfaff_hh_
#define _pfaff_hh_

 
#include "matrix.hpp"
#include "matrix-con.hpp"
 
class MatrixConstructor;

 
class PfaffianComputation : public our_new_delete
{
  const Ring *R;
  const Matrix *M;
  MatrixConstructor pfaffs;
  // One row matrix collecting non-zero pfaffians
 
  int p;
  bool done;
  size_t *row_set;
 
  ring_elem calc_pfaff(size_t *r, int p);
  // Compute the pfaffian of the minor with rows
  // and columns r[0]..r[p-1]
 
  int step();
  // Compute one more pfaffian of size p.
 
 public:
  PfaffianComputation(const Matrix *M, int p);
  ~PfaffianComputation();
 
  int calc(int nsteps = -1);
  // Compute nsteps pfaffians.  Only non-negative ones are appended
  // -1 means compute all of them.
 
  Matrix *pfaffians() { return pfaffs.to_matrix(); }
  const Ring *get_ring() const { return R; }
  ring_elem calc_pfaff(void);
};
 
#endif
 
// Local Variables:
// compile-command: "make -C $M2BUILDDIR/Macaulay2/e "
// indent-tabs-mode: nil
// End: