3 * Implementation of symbolic matrices */
6 * GiNaC Copyright (C) 1999-2001 Johannes Gutenberg University Mainz, Germany
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
41 GINAC_IMPLEMENT_REGISTERED_CLASS(matrix, basic)
44 // default ctor, dtor, copy ctor, assignment operator and helpers:
49 /** Default ctor. Initializes to 1 x 1-dimensional zero-matrix. */
50 matrix::matrix() : inherited(TINFO_matrix), row(1), col(1)
52 debugmsg("matrix default ctor",LOGLEVEL_CONSTRUCT);
58 /** For use by copy ctor and assignment operator. */
59 void matrix::copy(const matrix & other)
61 inherited::copy(other);
64 m = other.m; // STL's vector copying invoked here
67 void matrix::destroy(bool call_parent)
69 if (call_parent) inherited::destroy(call_parent);
78 /** Very common ctor. Initializes to r x c-dimensional zero-matrix.
80 * @param r number of rows
81 * @param c number of cols */
82 matrix::matrix(unsigned r, unsigned c)
83 : inherited(TINFO_matrix), row(r), col(c)
85 debugmsg("matrix ctor from unsigned,unsigned",LOGLEVEL_CONSTRUCT);
86 m.resize(r*c, _ex0());
91 /** Ctor from representation, for internal use only. */
92 matrix::matrix(unsigned r, unsigned c, const exvector & m2)
93 : inherited(TINFO_matrix), row(r), col(c), m(m2)
95 debugmsg("matrix ctor from unsigned,unsigned,exvector",LOGLEVEL_CONSTRUCT);
102 /** Construct object from archive_node. */
103 matrix::matrix(const archive_node &n, const lst &sym_lst) : inherited(n, sym_lst)
105 debugmsg("matrix ctor from archive_node", LOGLEVEL_CONSTRUCT);
106 if (!(n.find_unsigned("row", row)) || !(n.find_unsigned("col", col)))
107 throw (std::runtime_error("unknown matrix dimensions in archive"));
108 m.reserve(row * col);
109 for (unsigned int i=0; true; i++) {
111 if (n.find_ex("m", e, sym_lst, i))
118 /** Unarchive the object. */
119 ex matrix::unarchive(const archive_node &n, const lst &sym_lst)
121 return (new matrix(n, sym_lst))->setflag(status_flags::dynallocated);
124 /** Archive the object. */
125 void matrix::archive(archive_node &n) const
127 inherited::archive(n);
128 n.add_unsigned("row", row);
129 n.add_unsigned("col", col);
130 exvector::const_iterator i = m.begin(), iend = m.end();
138 // functions overriding virtual functions from bases classes
143 void matrix::print(std::ostream & os, unsigned upper_precedence) const
145 debugmsg("matrix print",LOGLEVEL_PRINT);
147 for (unsigned r=0; r<row-1; ++r) {
149 for (unsigned c=0; c<col-1; ++c)
150 os << m[r*col+c] << ",";
151 os << m[col*(r+1)-1] << "]], ";
154 for (unsigned c=0; c<col-1; ++c)
155 os << m[(row-1)*col+c] << ",";
156 os << m[row*col-1] << "]] ]]";
159 void matrix::printraw(std::ostream & os) const
161 debugmsg("matrix printraw",LOGLEVEL_PRINT);
162 os << class_name() << "(" << row << "," << col <<",";
163 for (unsigned r=0; r<row-1; ++r) {
165 for (unsigned c=0; c<col-1; ++c)
166 os << m[r*col+c] << ",";
167 os << m[col*(r-1)-1] << "),";
170 for (unsigned c=0; c<col-1; ++c)
171 os << m[(row-1)*col+c] << ",";
172 os << m[row*col-1] << "))";
175 /** nops is defined to be rows x columns. */
176 unsigned matrix::nops() const
181 /** returns matrix entry at position (i/col, i%col). */
182 ex matrix::op(int i) const
187 /** returns matrix entry at position (i/col, i%col). */
188 ex & matrix::let_op(int i)
191 GINAC_ASSERT(i<nops());
196 /** expands the elements of a matrix entry by entry. */
197 ex matrix::expand(unsigned options) const
199 exvector tmp(row*col);
200 for (unsigned i=0; i<row*col; ++i)
201 tmp[i] = m[i].expand(options);
203 return matrix(row, col, tmp);
206 /** Search ocurrences. A matrix 'has' an expression if it is the expression
207 * itself or one of the elements 'has' it. */
208 bool matrix::has(const ex & other) const
210 GINAC_ASSERT(other.bp!=0);
212 // tautology: it is the expression itself
213 if (is_equal(*other.bp)) return true;
215 // search all the elements
216 for (exvector::const_iterator r=m.begin(); r!=m.end(); ++r)
217 if ((*r).has(other)) return true;
222 /** Evaluate matrix entry by entry. */
223 ex matrix::eval(int level) const
225 debugmsg("matrix eval",LOGLEVEL_MEMBER_FUNCTION);
227 // check if we have to do anything at all
228 if ((level==1)&&(flags & status_flags::evaluated))
232 if (level == -max_recursion_level)
233 throw (std::runtime_error("matrix::eval(): recursion limit exceeded"));
235 // eval() entry by entry
236 exvector m2(row*col);
238 for (unsigned r=0; r<row; ++r)
239 for (unsigned c=0; c<col; ++c)
240 m2[r*col+c] = m[r*col+c].eval(level);
242 return (new matrix(row, col, m2))->setflag(status_flags::dynallocated |
243 status_flags::evaluated );
246 /** Evaluate matrix numerically entry by entry. */
247 ex matrix::evalf(int level) const
249 debugmsg("matrix evalf",LOGLEVEL_MEMBER_FUNCTION);
251 // check if we have to do anything at all
256 if (level == -max_recursion_level) {
257 throw (std::runtime_error("matrix::evalf(): recursion limit exceeded"));
260 // evalf() entry by entry
261 exvector m2(row*col);
263 for (unsigned r=0; r<row; ++r)
264 for (unsigned c=0; c<col; ++c)
265 m2[r*col+c] = m[r*col+c].evalf(level);
267 return matrix(row, col, m2);
270 ex matrix::subs(const lst & ls, const lst & lr) const
272 exvector m2(row * col);
273 for (unsigned r=0; r<row; ++r)
274 for (unsigned c=0; c<col; ++c)
275 m2[r*col+c] = m[r*col+c].subs(ls, lr);
277 return matrix(row, col, m2);
282 int matrix::compare_same_type(const basic & other) const
284 GINAC_ASSERT(is_exactly_of_type(other, matrix));
285 const matrix & o = static_cast<matrix &>(const_cast<basic &>(other));
287 // compare number of rows
289 return row < o.rows() ? -1 : 1;
291 // compare number of columns
293 return col < o.cols() ? -1 : 1;
295 // equal number of rows and columns, compare individual elements
297 for (unsigned r=0; r<row; ++r) {
298 for (unsigned c=0; c<col; ++c) {
299 cmpval = ((*this)(r,c)).compare(o(r,c));
300 if (cmpval!=0) return cmpval;
303 // all elements are equal => matrices are equal;
307 /** Automatic symbolic evaluation of an indexed matrix. */
308 ex matrix::eval_indexed(const basic & i) const
310 GINAC_ASSERT(is_of_type(i, indexed));
311 GINAC_ASSERT(is_ex_of_type(i.op(0), matrix));
313 bool all_indices_unsigned = static_cast<const indexed &>(i).all_index_values_are(info_flags::nonnegint);
318 // One index, must be one-dimensional vector
319 if (row != 1 && col != 1)
320 throw (std::runtime_error("matrix::eval_indexed(): vector must have exactly 1 index"));
322 const idx & i1 = ex_to_idx(i.op(1));
327 if (!i1.get_dim().is_equal(row))
328 throw (std::runtime_error("matrix::eval_indexed(): dimension of index must match number of vector elements"));
330 // Index numeric -> return vector element
331 if (all_indices_unsigned) {
332 unsigned n1 = ex_to_numeric(i1.get_value()).to_int();
334 throw (std::runtime_error("matrix::eval_indexed(): value of index exceeds number of vector elements"));
335 return (*this)(n1, 0);
341 if (!i1.get_dim().is_equal(col))
342 throw (std::runtime_error("matrix::eval_indexed(): dimension of index must match number of vector elements"));
344 // Index numeric -> return vector element
345 if (all_indices_unsigned) {
346 unsigned n1 = ex_to_numeric(i1.get_value()).to_int();
348 throw (std::runtime_error("matrix::eval_indexed(): value of index exceeds number of vector elements"));
349 return (*this)(0, n1);
353 } else if (i.nops() == 3) {
356 const idx & i1 = ex_to_idx(i.op(1));
357 const idx & i2 = ex_to_idx(i.op(2));
359 if (!i1.get_dim().is_equal(row))
360 throw (std::runtime_error("matrix::eval_indexed(): dimension of first index must match number of rows"));
361 if (!i2.get_dim().is_equal(col))
362 throw (std::runtime_error("matrix::eval_indexed(): dimension of second index must match number of columns"));
364 // Pair of dummy indices -> compute trace
365 if (is_dummy_pair(i1, i2))
368 // Both indices numeric -> return matrix element
369 if (all_indices_unsigned) {
370 unsigned n1 = ex_to_numeric(i1.get_value()).to_int(), n2 = ex_to_numeric(i2.get_value()).to_int();
372 throw (std::runtime_error("matrix::eval_indexed(): value of first index exceeds number of rows"));
374 throw (std::runtime_error("matrix::eval_indexed(): value of second index exceeds number of columns"));
375 return (*this)(n1, n2);
379 throw (std::runtime_error("matrix::eval_indexed(): matrix must have exactly 2 indices"));
384 /** Contraction of an indexed matrix with something else. */
385 bool matrix::contract_with(exvector::iterator self, exvector::iterator other, exvector & v) const
387 GINAC_ASSERT(is_ex_of_type(*self, indexed));
388 GINAC_ASSERT(is_ex_of_type(*other, indexed));
389 GINAC_ASSERT(self->nops() == 2 || self->nops() == 3);
390 GINAC_ASSERT(is_ex_of_type(self->op(0), matrix));
392 // Only contract with other matrices
393 if (!is_ex_of_type(other->op(0), matrix))
396 GINAC_ASSERT(other->nops() == 2 || other->nops() == 3);
398 const matrix &self_matrix = ex_to_matrix(self->op(0));
399 const matrix &other_matrix = ex_to_matrix(other->op(0));
401 if (self->nops() == 2) {
402 unsigned self_dim = (self_matrix.col == 1) ? self_matrix.row : self_matrix.col;
404 if (other->nops() == 2) { // vector * vector (scalar product)
405 unsigned other_dim = (other_matrix.col == 1) ? other_matrix.row : other_matrix.col;
407 if (self_matrix.col == 1) {
408 if (other_matrix.col == 1) {
409 // Column vector * column vector, transpose first vector
410 *self = self_matrix.transpose().mul(other_matrix)(0, 0);
412 // Column vector * row vector, swap factors
413 *self = other_matrix.mul(self_matrix)(0, 0);
416 if (other_matrix.col == 1) {
417 // Row vector * column vector, perfect
418 *self = self_matrix.mul(other_matrix)(0, 0);
420 // Row vector * row vector, transpose second vector
421 *self = self_matrix.mul(other_matrix.transpose())(0, 0);
427 } else { // vector * matrix
429 // B_i * A_ij = (B*A)_j (B is row vector)
430 if (is_dummy_pair(self->op(1), other->op(1))) {
431 if (self_matrix.row == 1)
432 *self = indexed(self_matrix.mul(other_matrix), other->op(2));
434 *self = indexed(self_matrix.transpose().mul(other_matrix), other->op(2));
439 // B_j * A_ij = (A*B)_i (B is column vector)
440 if (is_dummy_pair(self->op(1), other->op(2))) {
441 if (self_matrix.col == 1)
442 *self = indexed(other_matrix.mul(self_matrix), other->op(1));
444 *self = indexed(other_matrix.mul(self_matrix.transpose()), other->op(1));
450 } else if (other->nops() == 3) { // matrix * matrix
452 // A_ij * B_jk = (A*B)_ik
453 if (is_dummy_pair(self->op(2), other->op(1))) {
454 *self = indexed(self_matrix.mul(other_matrix), self->op(1), other->op(2));
459 // A_ij * B_kj = (A*Btrans)_ik
460 if (is_dummy_pair(self->op(2), other->op(2))) {
461 *self = indexed(self_matrix.mul(other_matrix.transpose()), self->op(1), other->op(1));
466 // A_ji * B_jk = (Atrans*B)_ik
467 if (is_dummy_pair(self->op(1), other->op(1))) {
468 *self = indexed(self_matrix.transpose().mul(other_matrix), self->op(2), other->op(2));
473 // A_ji * B_kj = (B*A)_ki
474 if (is_dummy_pair(self->op(1), other->op(2))) {
475 *self = indexed(other_matrix.mul(self_matrix), other->op(1), self->op(2));
486 // non-virtual functions in this class
493 * @exception logic_error (incompatible matrices) */
494 matrix matrix::add(const matrix & other) const
496 if (col != other.col || row != other.row)
497 throw (std::logic_error("matrix::add(): incompatible matrices"));
499 exvector sum(this->m);
500 exvector::iterator i;
501 exvector::const_iterator ci;
502 for (i=sum.begin(), ci=other.m.begin(); i!=sum.end(); ++i, ++ci)
505 return matrix(row,col,sum);
509 /** Difference of matrices.
511 * @exception logic_error (incompatible matrices) */
512 matrix matrix::sub(const matrix & other) const
514 if (col != other.col || row != other.row)
515 throw (std::logic_error("matrix::sub(): incompatible matrices"));
517 exvector dif(this->m);
518 exvector::iterator i;
519 exvector::const_iterator ci;
520 for (i=dif.begin(), ci=other.m.begin(); i!=dif.end(); ++i, ++ci)
523 return matrix(row,col,dif);
527 /** Product of matrices.
529 * @exception logic_error (incompatible matrices) */
530 matrix matrix::mul(const matrix & other) const
532 if (this->cols() != other.rows())
533 throw (std::logic_error("matrix::mul(): incompatible matrices"));
535 exvector prod(this->rows()*other.cols());
537 for (unsigned r1=0; r1<this->rows(); ++r1) {
538 for (unsigned c=0; c<this->cols(); ++c) {
539 if (m[r1*col+c].is_zero())
541 for (unsigned r2=0; r2<other.cols(); ++r2)
542 prod[r1*other.col+r2] += (m[r1*col+c] * other.m[c*other.col+r2]).expand();
545 return matrix(row, other.col, prod);
549 /** operator() to access elements.
551 * @param ro row of element
552 * @param co column of element
553 * @exception range_error (index out of range) */
554 const ex & matrix::operator() (unsigned ro, unsigned co) const
556 if (ro>=row || co>=col)
557 throw (std::range_error("matrix::operator(): index out of range"));
563 /** Set individual elements manually.
565 * @exception range_error (index out of range) */
566 matrix & matrix::set(unsigned ro, unsigned co, ex value)
568 if (ro>=row || co>=col)
569 throw (std::range_error("matrix::set(): index out of range"));
571 ensure_if_modifiable();
572 m[ro*col+co] = value;
577 /** Transposed of an m x n matrix, producing a new n x m matrix object that
578 * represents the transposed. */
579 matrix matrix::transpose(void) const
581 exvector trans(this->cols()*this->rows());
583 for (unsigned r=0; r<this->cols(); ++r)
584 for (unsigned c=0; c<this->rows(); ++c)
585 trans[r*this->rows()+c] = m[c*this->cols()+r];
587 return matrix(this->cols(),this->rows(),trans);
591 /** Determinant of square matrix. This routine doesn't actually calculate the
592 * determinant, it only implements some heuristics about which algorithm to
593 * run. If all the elements of the matrix are elements of an integral domain
594 * the determinant is also in that integral domain and the result is expanded
595 * only. If one or more elements are from a quotient field the determinant is
596 * usually also in that quotient field and the result is normalized before it
597 * is returned. This implies that the determinant of the symbolic 2x2 matrix
598 * [[a/(a-b),1],[b/(a-b),1]] is returned as unity. (In this respect, it
599 * behaves like MapleV and unlike Mathematica.)
601 * @param algo allows to chose an algorithm
602 * @return the determinant as a new expression
603 * @exception logic_error (matrix not square)
604 * @see determinant_algo */
605 ex matrix::determinant(unsigned algo) const
608 throw (std::logic_error("matrix::determinant(): matrix not square"));
609 GINAC_ASSERT(row*col==m.capacity());
611 // Gather some statistical information about this matrix:
612 bool numeric_flag = true;
613 bool normal_flag = false;
614 unsigned sparse_count = 0; // counts non-zero elements
615 for (exvector::const_iterator r=m.begin(); r!=m.end(); ++r) {
616 lst srl; // symbol replacement list
617 ex rtest = (*r).to_rational(srl);
618 if (!rtest.is_zero())
620 if (!rtest.info(info_flags::numeric))
621 numeric_flag = false;
622 if (!rtest.info(info_flags::crational_polynomial) &&
623 rtest.info(info_flags::rational_function))
627 // Here is the heuristics in case this routine has to decide:
628 if (algo == determinant_algo::automatic) {
629 // Minor expansion is generally a good guess:
630 algo = determinant_algo::laplace;
631 // Does anybody know when a matrix is really sparse?
632 // Maybe <~row/2.236 nonzero elements average in a row?
633 if (row>3 && 5*sparse_count<=row*col)
634 algo = determinant_algo::bareiss;
635 // Purely numeric matrix can be handled by Gauss elimination.
636 // This overrides any prior decisions.
638 algo = determinant_algo::gauss;
641 // Trap the trivial case here, since some algorithms don't like it
643 // for consistency with non-trivial determinants...
645 return m[0].normal();
647 return m[0].expand();
650 // Compute the determinant
652 case determinant_algo::gauss: {
655 int sign = tmp.gauss_elimination(true);
656 for (unsigned d=0; d<row; ++d)
657 det *= tmp.m[d*col+d];
659 return (sign*det).normal();
661 return (sign*det).normal().expand();
663 case determinant_algo::bareiss: {
666 sign = tmp.fraction_free_elimination(true);
668 return (sign*tmp.m[row*col-1]).normal();
670 return (sign*tmp.m[row*col-1]).expand();
672 case determinant_algo::divfree: {
675 sign = tmp.division_free_elimination(true);
678 ex det = tmp.m[row*col-1];
679 // factor out accumulated bogus slag
680 for (unsigned d=0; d<row-2; ++d)
681 for (unsigned j=0; j<row-d-2; ++j)
682 det = (det/tmp.m[d*col+d]).normal();
685 case determinant_algo::laplace:
687 // This is the minor expansion scheme. We always develop such
688 // that the smallest minors (i.e, the trivial 1x1 ones) are on the
689 // rightmost column. For this to be efficient it turns out that
690 // the emptiest columns (i.e. the ones with most zeros) should be
691 // the ones on the right hand side. Therefore we presort the
692 // columns of the matrix:
693 typedef std::pair<unsigned,unsigned> uintpair;
694 std::vector<uintpair> c_zeros; // number of zeros in column
695 for (unsigned c=0; c<col; ++c) {
697 for (unsigned r=0; r<row; ++r)
698 if (m[r*col+c].is_zero())
700 c_zeros.push_back(uintpair(acc,c));
702 sort(c_zeros.begin(),c_zeros.end());
703 std::vector<unsigned> pre_sort;
704 for (std::vector<uintpair>::iterator i=c_zeros.begin(); i!=c_zeros.end(); ++i)
705 pre_sort.push_back(i->second);
706 int sign = permutation_sign(pre_sort);
707 exvector result(row*col); // represents sorted matrix
709 for (std::vector<unsigned>::iterator i=pre_sort.begin();
712 for (unsigned r=0; r<row; ++r)
713 result[r*col+c] = m[r*col+(*i)];
717 return (sign*matrix(row,col,result).determinant_minor()).normal();
719 return sign*matrix(row,col,result).determinant_minor();
725 /** Trace of a matrix. The result is normalized if it is in some quotient
726 * field and expanded only otherwise. This implies that the trace of the
727 * symbolic 2x2 matrix [[a/(a-b),x],[y,b/(b-a)]] is recognized to be unity.
729 * @return the sum of diagonal elements
730 * @exception logic_error (matrix not square) */
731 ex matrix::trace(void) const
734 throw (std::logic_error("matrix::trace(): matrix not square"));
737 for (unsigned r=0; r<col; ++r)
740 if (tr.info(info_flags::rational_function) &&
741 !tr.info(info_flags::crational_polynomial))
748 /** Characteristic Polynomial. Following mathematica notation the
749 * characteristic polynomial of a matrix M is defined as the determiant of
750 * (M - lambda * 1) where 1 stands for the unit matrix of the same dimension
751 * as M. Note that some CASs define it with a sign inside the determinant
752 * which gives rise to an overall sign if the dimension is odd. This method
753 * returns the characteristic polynomial collected in powers of lambda as a
756 * @return characteristic polynomial as new expression
757 * @exception logic_error (matrix not square)
758 * @see matrix::determinant() */
759 ex matrix::charpoly(const symbol & lambda) const
762 throw (std::logic_error("matrix::charpoly(): matrix not square"));
764 bool numeric_flag = true;
765 for (exvector::const_iterator r=m.begin(); r!=m.end(); ++r) {
766 if (!(*r).info(info_flags::numeric)) {
767 numeric_flag = false;
771 // The pure numeric case is traditionally rather common. Hence, it is
772 // trapped and we use Leverrier's algorithm which goes as row^3 for
773 // every coefficient. The expensive part is the matrix multiplication.
777 ex poly = power(lambda,row)-c*power(lambda,row-1);
778 for (unsigned i=1; i<row; ++i) {
779 for (unsigned j=0; j<row; ++j)
782 c = B.trace()/ex(i+1);
783 poly -= c*power(lambda,row-i-1);
792 for (unsigned r=0; r<col; ++r)
793 M.m[r*col+r] -= lambda;
795 return M.determinant().collect(lambda);
799 /** Inverse of this matrix.
801 * @return the inverted matrix
802 * @exception logic_error (matrix not square)
803 * @exception runtime_error (singular matrix) */
804 matrix matrix::inverse(void) const
807 throw (std::logic_error("matrix::inverse(): matrix not square"));
809 // NOTE: the Gauss-Jordan elimination used here can in principle be
810 // replaced by two clever calls to gauss_elimination() and some to
811 // transpose(). Wouldn't be more efficient (maybe less?), just more
814 // set tmp to the unit matrix
815 for (unsigned i=0; i<col; ++i)
816 tmp.m[i*col+i] = _ex1();
818 // create a copy of this matrix
820 for (unsigned r1=0; r1<row; ++r1) {
821 int indx = cpy.pivot(r1, r1);
823 throw (std::runtime_error("matrix::inverse(): singular matrix"));
825 if (indx != 0) { // swap rows r and indx of matrix tmp
826 for (unsigned i=0; i<col; ++i)
827 tmp.m[r1*col+i].swap(tmp.m[indx*col+i]);
829 ex a1 = cpy.m[r1*col+r1];
830 for (unsigned c=0; c<col; ++c) {
831 cpy.m[r1*col+c] /= a1;
832 tmp.m[r1*col+c] /= a1;
834 for (unsigned r2=0; r2<row; ++r2) {
836 if (!cpy.m[r2*col+r1].is_zero()) {
837 ex a2 = cpy.m[r2*col+r1];
838 // yes, there is something to do in this column
839 for (unsigned c=0; c<col; ++c) {
840 cpy.m[r2*col+c] -= a2 * cpy.m[r1*col+c];
841 if (!cpy.m[r2*col+c].info(info_flags::numeric))
842 cpy.m[r2*col+c] = cpy.m[r2*col+c].normal();
843 tmp.m[r2*col+c] -= a2 * tmp.m[r1*col+c];
844 if (!tmp.m[r2*col+c].info(info_flags::numeric))
845 tmp.m[r2*col+c] = tmp.m[r2*col+c].normal();
856 /** Solve a linear system consisting of a m x n matrix and a m x p right hand
857 * side by applying an elimination scheme to the augmented matrix.
859 * @param vars n x p matrix, all elements must be symbols
860 * @param rhs m x p matrix
861 * @return n x p solution matrix
862 * @exception logic_error (incompatible matrices)
863 * @exception invalid_argument (1st argument must be matrix of symbols)
864 * @exception runtime_error (inconsistent linear system)
866 matrix matrix::solve(const matrix & vars,
870 const unsigned m = this->rows();
871 const unsigned n = this->cols();
872 const unsigned p = rhs.cols();
875 if ((rhs.rows() != m) || (vars.rows() != n) || (vars.col != p))
876 throw (std::logic_error("matrix::solve(): incompatible matrices"));
877 for (unsigned ro=0; ro<n; ++ro)
878 for (unsigned co=0; co<p; ++co)
879 if (!vars(ro,co).info(info_flags::symbol))
880 throw (std::invalid_argument("matrix::solve(): 1st argument must be matrix of symbols"));
882 // build the augmented matrix of *this with rhs attached to the right
884 for (unsigned r=0; r<m; ++r) {
885 for (unsigned c=0; c<n; ++c)
886 aug.m[r*(n+p)+c] = this->m[r*n+c];
887 for (unsigned c=0; c<p; ++c)
888 aug.m[r*(n+p)+c+n] = rhs.m[r*p+c];
891 // Gather some statistical information about the augmented matrix:
892 bool numeric_flag = true;
893 for (exvector::const_iterator r=aug.m.begin(); r!=aug.m.end(); ++r) {
894 if (!(*r).info(info_flags::numeric))
895 numeric_flag = false;
898 // Here is the heuristics in case this routine has to decide:
899 if (algo == solve_algo::automatic) {
900 // Bareiss (fraction-free) elimination is generally a good guess:
901 algo = solve_algo::bareiss;
902 // For m<3, Bareiss elimination is equivalent to division free
903 // elimination but has more logistic overhead
905 algo = solve_algo::divfree;
906 // This overrides any prior decisions.
908 algo = solve_algo::gauss;
911 // Eliminate the augmented matrix:
913 case solve_algo::gauss:
914 aug.gauss_elimination();
915 case solve_algo::divfree:
916 aug.division_free_elimination();
917 case solve_algo::bareiss:
919 aug.fraction_free_elimination();
922 // assemble the solution matrix:
924 for (unsigned co=0; co<p; ++co) {
925 unsigned last_assigned_sol = n+1;
926 for (int r=m-1; r>=0; --r) {
927 unsigned fnz = 1; // first non-zero in row
928 while ((fnz<=n) && (aug.m[r*(n+p)+(fnz-1)].is_zero()))
931 // row consists only of zeros, corresponding rhs must be 0, too
932 if (!aug.m[r*(n+p)+n+co].is_zero()) {
933 throw (std::runtime_error("matrix::solve(): inconsistent linear system"));
936 // assign solutions for vars between fnz+1 and
937 // last_assigned_sol-1: free parameters
938 for (unsigned c=fnz; c<last_assigned_sol-1; ++c)
939 sol.set(c,co,vars.m[c*p+co]);
940 ex e = aug.m[r*(n+p)+n+co];
941 for (unsigned c=fnz; c<n; ++c)
942 e -= aug.m[r*(n+p)+c]*sol.m[c*p+co];
944 (e/(aug.m[r*(n+p)+(fnz-1)])).normal());
945 last_assigned_sol = fnz;
948 // assign solutions for vars between 1 and
949 // last_assigned_sol-1: free parameters
950 for (unsigned ro=0; ro<last_assigned_sol-1; ++ro)
951 sol.set(ro,co,vars(ro,co));
960 /** Recursive determinant for small matrices having at least one symbolic
961 * entry. The basic algorithm, known as Laplace-expansion, is enhanced by
962 * some bookkeeping to avoid calculation of the same submatrices ("minors")
963 * more than once. According to W.M.Gentleman and S.C.Johnson this algorithm
964 * is better than elimination schemes for matrices of sparse multivariate
965 * polynomials and also for matrices of dense univariate polynomials if the
966 * matrix' dimesion is larger than 7.
968 * @return the determinant as a new expression (in expanded form)
969 * @see matrix::determinant() */
970 ex matrix::determinant_minor(void) const
972 // for small matrices the algorithm does not make any sense:
973 const unsigned n = this->cols();
975 return m[0].expand();
977 return (m[0]*m[3]-m[2]*m[1]).expand();
979 return (m[0]*m[4]*m[8]-m[0]*m[5]*m[7]-
980 m[1]*m[3]*m[8]+m[2]*m[3]*m[7]+
981 m[1]*m[5]*m[6]-m[2]*m[4]*m[6]).expand();
983 // This algorithm can best be understood by looking at a naive
984 // implementation of Laplace-expansion, like this one:
986 // matrix minorM(this->rows()-1,this->cols()-1);
987 // for (unsigned r1=0; r1<this->rows(); ++r1) {
988 // // shortcut if element(r1,0) vanishes
989 // if (m[r1*col].is_zero())
991 // // assemble the minor matrix
992 // for (unsigned r=0; r<minorM.rows(); ++r) {
993 // for (unsigned c=0; c<minorM.cols(); ++c) {
995 // minorM.set(r,c,m[r*col+c+1]);
997 // minorM.set(r,c,m[(r+1)*col+c+1]);
1000 // // recurse down and care for sign:
1002 // det -= m[r1*col] * minorM.determinant_minor();
1004 // det += m[r1*col] * minorM.determinant_minor();
1006 // return det.expand();
1007 // What happens is that while proceeding down many of the minors are
1008 // computed more than once. In particular, there are binomial(n,k)
1009 // kxk minors and each one is computed factorial(n-k) times. Therefore
1010 // it is reasonable to store the results of the minors. We proceed from
1011 // right to left. At each column c we only need to retrieve the minors
1012 // calculated in step c-1. We therefore only have to store at most
1013 // 2*binomial(n,n/2) minors.
1015 // Unique flipper counter for partitioning into minors
1016 std::vector<unsigned> Pkey;
1018 // key for minor determinant (a subpartition of Pkey)
1019 std::vector<unsigned> Mkey;
1021 // we store our subminors in maps, keys being the rows they arise from
1022 typedef std::map<std::vector<unsigned>,class ex> Rmap;
1023 typedef std::map<std::vector<unsigned>,class ex>::value_type Rmap_value;
1027 // initialize A with last column:
1028 for (unsigned r=0; r<n; ++r) {
1029 Pkey.erase(Pkey.begin(),Pkey.end());
1031 A.insert(Rmap_value(Pkey,m[n*(r+1)-1]));
1033 // proceed from right to left through matrix
1034 for (int c=n-2; c>=0; --c) {
1035 Pkey.erase(Pkey.begin(),Pkey.end()); // don't change capacity
1036 Mkey.erase(Mkey.begin(),Mkey.end());
1037 for (unsigned i=0; i<n-c; ++i)
1039 unsigned fc = 0; // controls logic for our strange flipper counter
1042 for (unsigned r=0; r<n-c; ++r) {
1043 // maybe there is nothing to do?
1044 if (m[Pkey[r]*n+c].is_zero())
1046 // create the sorted key for all possible minors
1047 Mkey.erase(Mkey.begin(),Mkey.end());
1048 for (unsigned i=0; i<n-c; ++i)
1050 Mkey.push_back(Pkey[i]);
1051 // Fetch the minors and compute the new determinant
1053 det -= m[Pkey[r]*n+c]*A[Mkey];
1055 det += m[Pkey[r]*n+c]*A[Mkey];
1057 // prevent build-up of deep nesting of expressions saves time:
1059 // store the new determinant at its place in B:
1061 B.insert(Rmap_value(Pkey,det));
1062 // increment our strange flipper counter
1063 for (fc=n-c; fc>0; --fc) {
1065 if (Pkey[fc-1]<fc+c)
1069 for (unsigned j=fc; j<n-c; ++j)
1070 Pkey[j] = Pkey[j-1]+1;
1072 // next column, so change the role of A and B:
1081 /** Perform the steps of an ordinary Gaussian elimination to bring the m x n
1082 * matrix into an upper echelon form. The algorithm is ok for matrices
1083 * with numeric coefficients but quite unsuited for symbolic matrices.
1085 * @param det may be set to true to save a lot of space if one is only
1086 * interested in the diagonal elements (i.e. for calculating determinants).
1087 * The others are set to zero in this case.
1088 * @return sign is 1 if an even number of rows was swapped, -1 if an odd
1089 * number of rows was swapped and 0 if the matrix is singular. */
1090 int matrix::gauss_elimination(const bool det)
1092 ensure_if_modifiable();
1093 const unsigned m = this->rows();
1094 const unsigned n = this->cols();
1095 GINAC_ASSERT(!det || n==m);
1099 for (unsigned r1=0; (r1<n-1)&&(r0<m-1); ++r1) {
1100 int indx = pivot(r0, r1, true);
1104 return 0; // leaves *this in a messy state
1109 for (unsigned r2=r0+1; r2<m; ++r2) {
1110 if (!this->m[r2*n+r1].is_zero()) {
1111 // yes, there is something to do in this row
1112 ex piv = this->m[r2*n+r1] / this->m[r0*n+r1];
1113 for (unsigned c=r1+1; c<n; ++c) {
1114 this->m[r2*n+c] -= piv * this->m[r0*n+c];
1115 if (!this->m[r2*n+c].info(info_flags::numeric))
1116 this->m[r2*n+c] = this->m[r2*n+c].normal();
1119 // fill up left hand side with zeros
1120 for (unsigned c=0; c<=r1; ++c)
1121 this->m[r2*n+c] = _ex0();
1124 // save space by deleting no longer needed elements
1125 for (unsigned c=r0+1; c<n; ++c)
1126 this->m[r0*n+c] = _ex0();
1136 /** Perform the steps of division free elimination to bring the m x n matrix
1137 * into an upper echelon form.
1139 * @param det may be set to true to save a lot of space if one is only
1140 * interested in the diagonal elements (i.e. for calculating determinants).
1141 * The others are set to zero in this case.
1142 * @return sign is 1 if an even number of rows was swapped, -1 if an odd
1143 * number of rows was swapped and 0 if the matrix is singular. */
1144 int matrix::division_free_elimination(const bool det)
1146 ensure_if_modifiable();
1147 const unsigned m = this->rows();
1148 const unsigned n = this->cols();
1149 GINAC_ASSERT(!det || n==m);
1153 for (unsigned r1=0; (r1<n-1)&&(r0<m-1); ++r1) {
1154 int indx = pivot(r0, r1, true);
1158 return 0; // leaves *this in a messy state
1163 for (unsigned r2=r0+1; r2<m; ++r2) {
1164 for (unsigned c=r1+1; c<n; ++c)
1165 this->m[r2*n+c] = (this->m[r0*n+r1]*this->m[r2*n+c] - this->m[r2*n+r1]*this->m[r0*n+c]).expand();
1166 // fill up left hand side with zeros
1167 for (unsigned c=0; c<=r1; ++c)
1168 this->m[r2*n+c] = _ex0();
1171 // save space by deleting no longer needed elements
1172 for (unsigned c=r0+1; c<n; ++c)
1173 this->m[r0*n+c] = _ex0();
1183 /** Perform the steps of Bareiss' one-step fraction free elimination to bring
1184 * the matrix into an upper echelon form. Fraction free elimination means
1185 * that divide is used straightforwardly, without computing GCDs first. This
1186 * is possible, since we know the divisor at each step.
1188 * @param det may be set to true to save a lot of space if one is only
1189 * interested in the last element (i.e. for calculating determinants). The
1190 * others are set to zero in this case.
1191 * @return sign is 1 if an even number of rows was swapped, -1 if an odd
1192 * number of rows was swapped and 0 if the matrix is singular. */
1193 int matrix::fraction_free_elimination(const bool det)
1196 // (single-step fraction free elimination scheme, already known to Jordan)
1198 // Usual division-free elimination sets m[0](r,c) = m(r,c) and then sets
1199 // m[k+1](r,c) = m[k](k,k) * m[k](r,c) - m[k](r,k) * m[k](k,c).
1201 // Bareiss (fraction-free) elimination in addition divides that element
1202 // by m[k-1](k-1,k-1) for k>1, where it can be shown by means of the
1203 // Sylvester determinant that this really divides m[k+1](r,c).
1205 // We also allow rational functions where the original prove still holds.
1206 // However, we must care for numerator and denominator separately and
1207 // "manually" work in the integral domains because of subtle cancellations
1208 // (see below). This blows up the bookkeeping a bit and the formula has
1209 // to be modified to expand like this (N{x} stands for numerator of x,
1210 // D{x} for denominator of x):
1211 // N{m[k+1](r,c)} = N{m[k](k,k)}*N{m[k](r,c)}*D{m[k](r,k)}*D{m[k](k,c)}
1212 // -N{m[k](r,k)}*N{m[k](k,c)}*D{m[k](k,k)}*D{m[k](r,c)}
1213 // D{m[k+1](r,c)} = D{m[k](k,k)}*D{m[k](r,c)}*D{m[k](r,k)}*D{m[k](k,c)}
1214 // where for k>1 we now divide N{m[k+1](r,c)} by
1215 // N{m[k-1](k-1,k-1)}
1216 // and D{m[k+1](r,c)} by
1217 // D{m[k-1](k-1,k-1)}.
1219 ensure_if_modifiable();
1220 const unsigned m = this->rows();
1221 const unsigned n = this->cols();
1222 GINAC_ASSERT(!det || n==m);
1231 // We populate temporary matrices to subsequently operate on. There is
1232 // one holding numerators and another holding denominators of entries.
1233 // This is a must since the evaluator (or even earlier mul's constructor)
1234 // might cancel some trivial element which causes divide() to fail. The
1235 // elements are normalized first (yes, even though this algorithm doesn't
1236 // need GCDs) since the elements of *this might be unnormalized, which
1237 // makes things more complicated than they need to be.
1238 matrix tmp_n(*this);
1239 matrix tmp_d(m,n); // for denominators, if needed
1240 lst srl; // symbol replacement list
1241 exvector::iterator it = this->m.begin();
1242 exvector::iterator tmp_n_it = tmp_n.m.begin();
1243 exvector::iterator tmp_d_it = tmp_d.m.begin();
1244 for (; it!= this->m.end(); ++it, ++tmp_n_it, ++tmp_d_it) {
1245 (*tmp_n_it) = (*it).normal().to_rational(srl);
1246 (*tmp_d_it) = (*tmp_n_it).denom();
1247 (*tmp_n_it) = (*tmp_n_it).numer();
1251 for (unsigned r1=0; (r1<n-1)&&(r0<m-1); ++r1) {
1252 int indx = tmp_n.pivot(r0, r1, true);
1261 // tmp_n's rows r0 and indx were swapped, do the same in tmp_d:
1262 for (unsigned c=r1; c<n; ++c)
1263 tmp_d.m[n*indx+c].swap(tmp_d.m[n*r0+c]);
1265 for (unsigned r2=r0+1; r2<m; ++r2) {
1266 for (unsigned c=r1+1; c<n; ++c) {
1267 dividend_n = (tmp_n.m[r0*n+r1]*tmp_n.m[r2*n+c]*
1268 tmp_d.m[r2*n+r1]*tmp_d.m[r0*n+c]
1269 -tmp_n.m[r2*n+r1]*tmp_n.m[r0*n+c]*
1270 tmp_d.m[r0*n+r1]*tmp_d.m[r2*n+c]).expand();
1271 dividend_d = (tmp_d.m[r2*n+r1]*tmp_d.m[r0*n+c]*
1272 tmp_d.m[r0*n+r1]*tmp_d.m[r2*n+c]).expand();
1273 bool check = divide(dividend_n, divisor_n,
1274 tmp_n.m[r2*n+c], true);
1275 check &= divide(dividend_d, divisor_d,
1276 tmp_d.m[r2*n+c], true);
1277 GINAC_ASSERT(check);
1279 // fill up left hand side with zeros
1280 for (unsigned c=0; c<=r1; ++c)
1281 tmp_n.m[r2*n+c] = _ex0();
1283 if ((r1<n-1)&&(r0<m-1)) {
1284 // compute next iteration's divisor
1285 divisor_n = tmp_n.m[r0*n+r1].expand();
1286 divisor_d = tmp_d.m[r0*n+r1].expand();
1288 // save space by deleting no longer needed elements
1289 for (unsigned c=0; c<n; ++c) {
1290 tmp_n.m[r0*n+c] = _ex0();
1291 tmp_d.m[r0*n+c] = _ex1();
1298 // repopulate *this matrix:
1299 it = this->m.begin();
1300 tmp_n_it = tmp_n.m.begin();
1301 tmp_d_it = tmp_d.m.begin();
1302 for (; it!= this->m.end(); ++it, ++tmp_n_it, ++tmp_d_it)
1303 (*it) = ((*tmp_n_it)/(*tmp_d_it)).subs(srl);
1309 /** Partial pivoting method for matrix elimination schemes.
1310 * Usual pivoting (symbolic==false) returns the index to the element with the
1311 * largest absolute value in column ro and swaps the current row with the one
1312 * where the element was found. With (symbolic==true) it does the same thing
1313 * with the first non-zero element.
1315 * @param ro is the row from where to begin
1316 * @param co is the column to be inspected
1317 * @param symbolic signal if we want the first non-zero element to be pivoted
1318 * (true) or the one with the largest absolute value (false).
1319 * @return 0 if no interchange occured, -1 if all are zero (usually signaling
1320 * a degeneracy) and positive integer k means that rows ro and k were swapped.
1322 int matrix::pivot(unsigned ro, unsigned co, bool symbolic)
1326 // search first non-zero element in column co beginning at row ro
1327 while ((k<row) && (this->m[k*col+co].expand().is_zero()))
1330 // search largest element in column co beginning at row ro
1331 GINAC_ASSERT(is_ex_of_type(this->m[k*col+co],numeric));
1332 unsigned kmax = k+1;
1333 numeric mmax = abs(ex_to_numeric(m[kmax*col+co]));
1335 GINAC_ASSERT(is_ex_of_type(this->m[kmax*col+co],numeric));
1336 numeric tmp = ex_to_numeric(this->m[kmax*col+co]);
1337 if (abs(tmp) > mmax) {
1343 if (!mmax.is_zero())
1347 // all elements in column co below row ro vanish
1350 // matrix needs no pivoting
1352 // matrix needs pivoting, so swap rows k and ro
1353 ensure_if_modifiable();
1354 for (unsigned c=0; c<col; ++c)
1355 this->m[k*col+c].swap(this->m[ro*col+c]);
1360 /** Convert list of lists to matrix. */
1361 ex lst_to_matrix(const ex &l)
1363 if (!is_ex_of_type(l, lst))
1364 throw(std::invalid_argument("argument to lst_to_matrix() must be a lst"));
1366 // Find number of rows and columns
1367 unsigned rows = l.nops(), cols = 0, i, j;
1368 for (i=0; i<rows; i++)
1369 if (l.op(i).nops() > cols)
1370 cols = l.op(i).nops();
1372 // Allocate and fill matrix
1373 matrix &m = *new matrix(rows, cols);
1374 for (i=0; i<rows; i++)
1375 for (j=0; j<cols; j++)
1376 if (l.op(i).nops() > j)
1377 m.set(i, j, l.op(i).op(j));
1383 } // namespace GiNaC