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// Copyright 1996 Michael E. Stillman.
#ifndef _pfaff_hh_
#define _pfaff_hh_
#include "matrix.hpp"
#include "matrix-con.hpp"
class MatrixConstructor;
/**
@ingroup comp
@brief Computation of pfaffians of a skew symmetric matrix.
*/
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; }
};
#endif
// Local Variables:
// compile-command: "make -C $M2BUILDDIR/Macaulay2/e "
// indent-tabs-mode: nil
// End:
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