* computation, square-free factorization and rational function normalization. */
/*
- * GiNaC Copyright (C) 1999-2016 Johannes Gutenberg University Mainz, Germany
+ * GiNaC Copyright (C) 1999-2018 Johannes Gutenberg University Mainz, Germany
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
/** Maximum number of terms of leading coefficient of symbol in both polynomials */
size_t max_lcnops;
- /** Commparison operator for sorting */
+ /** Comparison operator for sorting */
bool operator<(const sym_desc &x) const
{
if (max_deg == x.max_deg)
return dynallocate<add>(v);
} else if (is_exactly_a<power>(e)) {
if (!is_a<symbol>(e.op(0))) {
- // (b^e)*lcm -> (b*lcm^(1/e))^e if lcm^(1/e) â\88\88 â\84\9d (i.e. not a float)
+ // (b^e)*lcm -> (b*lcm^(1/e))^e if lcm^(1/e) â\88\88 â\84\9a (i.e. not a float)
// but not for symbolic b, as evaluation would undo this again
numeric root_of_lcm = lcm.power(ex_to<numeric>(e.op(1)).inverse());
if (root_of_lcm.is_rational())
// The symbol with least degree which is contained in both polynomials
// is our main variable
- sym_desc_vec::iterator vari = sym_stats.begin();
+ auto vari = sym_stats.begin();
while ((vari != sym_stats.end()) &&
(((vari->ldeg_b == 0) && (vari->deg_b == 0)) ||
((vari->ldeg_a == 0) && (vari->deg_a == 0))))
* @param a multivariate polynomial over Z[X], treated here as univariate
* polynomial in x (needs not be expanded).
* @param x variable to factor in
- * @return vector of factors sorted in ascending degree */
-static exvector sqrfree_yun(const ex &a, const symbol &x)
+ * @return vector of expairs (factor, exponent), sorted by exponents */
+static epvector sqrfree_yun(const ex &a, const symbol &x)
{
- exvector res;
ex w = a;
ex z = w.diff(x);
ex g = gcd(w, z);
if (g.is_zero()) {
- return res;
+ return epvector{};
}
if (g.is_equal(_ex1)) {
- res.push_back(a);
- return res;
+ return epvector{expair(a, _ex1)};
}
- ex y;
+ epvector results;
+ ex exponent = _ex0;
do {
w = quo(w, g, x);
if (w.is_zero()) {
return res;
}
- y = quo(z, g, x);
- z = y - w.diff(x);
+ z = quo(z, g, x) - w.diff(x);
+ exponent = exponent + 1;
+ if (w.is_equal(x)) {
+ // shortcut for x^n with n ∈ ℕ
+ exponent += quo(z, w.diff(x), x);
+ results.push_back(expair(w, exponent));
+ break;
+ }
g = gcd(w, z);
- res.push_back(g);
+ if (!g.is_equal(_ex1)) {
+ results.push_back(expair(g, exponent));
+ }
} while (!z.is_zero());
- return res;
+ return results;
}
const ex tmp = multiply_lcm(a,lcm);
// find the factors
- exvector factors = sqrfree_yun(tmp, x);
+ epvector factors = sqrfree_yun(tmp, x);
- // construct the next list of symbols with the first element popped
- lst newargs = args;
- newargs.remove_first();
+ // remove symbol x and proceed recursively with the remaining symbols
+ args.remove_first();
// recurse down the factors in remaining variables
- if (newargs.nops()>0) {
+ if (args.nops()>0) {
for (auto & it : factors)
- it = sqrfree(it, newargs);
+ it.rest = sqrfree(it.rest, args);
}
// Done with recursion, now construct the final result
ex result = _ex1;
- int p = 1;
for (auto & it : factors)
- result *= pow(it, p++);
+ result *= pow(it.rest, it.coeff);
// Yun's algorithm does not account for constant factors. (For univariate
// polynomials it works only in the monic case.) We can correct this by
// inserting what has been lost back into the result. For completeness
// we'll also have to recurse down that factor in the remaining variables.
- if (newargs.nops()>0)
- result *= sqrfree(quo(tmp, result, x), newargs);
+ if (args.nops()>0)
+ result *= sqrfree(quo(tmp, result, x), args);
else
result *= quo(tmp, result, x);
//clog << "red_poly = " << red_poly << ", red_numer = " << red_numer << endl;
// Factorize denominator and compute cofactors
- exvector yun = sqrfree_yun(denom, x);
-//clog << "yun factors: " << exprseq(yun) << endl;
- size_t num_yun = yun.size();
- exvector factor; factor.reserve(num_yun);
- exvector cofac; cofac.reserve(num_yun);
- for (size_t i=0; i<num_yun; i++) {
- if (!yun[i].is_equal(_ex1)) {
- for (size_t j=0; j<=i; j++) {
- factor.push_back(pow(yun[i], j+1));
- ex prod = _ex1;
- for (size_t k=0; k<num_yun; k++) {
- if (k == i)
- prod *= pow(yun[k], i-j);
- else
- prod *= pow(yun[k], k+1);
- }
- cofac.push_back(prod.expand());
+ epvector yun = sqrfree_yun(denom, x);
+ size_t yun_max_exponent = yun.empty() ? 0 : ex_to<numeric>(yun.back().coeff).to_int();
+ exvector factor, cofac;
+ for (size_t i=0; i<yun.size(); i++) {
+ numeric i_exponent = ex_to<numeric>(yun[i].coeff);
+ for (size_t j=0; j<i_exponent; j++) {
+ factor.push_back(pow(yun[i].rest, j+1));
+ ex prod = _ex1;
+ for (size_t k=0; k<yun.size(); k++) {
+ if (yun[k].coeff == i_exponent)
+ prod *= pow(yun[k].rest, i_exponent-1-j);
+ else
+ prod *= pow(yun[k].rest, yun[k].coeff);
}
+ cofac.push_back(prod.expand());
}
}
size_t num_factors = factor.size();
return bp->to_rational(repl);
}
-// GiNaC 1.1 compatibility function
-ex ex::to_rational(lst & repl_lst) const
-{
- // Convert lst to exmap
- exmap m;
- for (auto & it : repl_lst)
- m.insert(std::make_pair(it.op(0), it.op(1)));
-
- ex ret = bp->to_rational(m);
-
- // Convert exmap back to lst
- repl_lst.remove_all();
- for (auto & it : m)
- repl_lst.append(it.first == it.second);
-
- return ret;
-}
-
ex ex::to_polynomial(exmap & repl) const
{
return bp->to_polynomial(repl);
}
-// GiNaC 1.1 compatibility function
-ex ex::to_polynomial(lst & repl_lst) const
-{
- // Convert lst to exmap
- exmap m;
- for (auto & it : repl_lst)
- m.insert(std::make_pair(it.op(0), it.op(1)));
-
- ex ret = bp->to_polynomial(m);
-
- // Convert exmap back to lst
- repl_lst.remove_all();
- for (auto & it : m)
- repl_lst.append(it.first == it.second);
-
- return ret;
-}
-
/** Default implementation of ex::to_rational(). This replaces the object with
* a temporary symbol. */
ex basic::to_rational(exmap & repl) const
git://www.ginac.de / ginac.git / blobdiff