From: Christian Bauer <Christian.Bauer@uni-mainz.de>
Date: Tue, 23 Jan 2001 19:14:36 +0000 (+0000)
Subject: replaced fraction addition algorithm with a slightly faster one (no polynomial
X-Git-Tag: release_0-7-1~16
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=075877089921f3555f040cd953a6ce75d0d544d8;ds=sidebyside

replaced fraction addition algorithm with a slightly faster one (no polynomial
divisions in loop)
---

diff --git a/ginac/normal.cpp b/ginac/normal.cpp
index 69a69452..067670ce 100644
--- a/ginac/normal.cpp
+++ b/ginac/normal.cpp
@@ -1914,9 +1914,11 @@ ex add::normal(lst &sym_lst, lst &repl_lst, int level) const
 	else if (level == -max_recursion_level)
 		throw(std::runtime_error("max recursion level reached"));
 
-	// Normalize and expand children, chop into summands
-	exvector o;
-	o.reserve(seq.size()+1);
+	// Normalize and expand children, chop into summands and split each
+	// one into numerator and denominator
+	exvector nums, dens;
+	nums.reserve(seq.size()+1);
+	dens.reserve(seq.size()+1);
 	epvector::const_iterator it = seq.begin(), itend = seq.end();
 	while (it != itend) {
 
@@ -1927,7 +1929,8 @@ ex add::normal(lst &sym_lst, lst &repl_lst, int level) const
 		if (is_ex_exactly_of_type(n.op(0), add)) {
 			epvector::const_iterator bit = ex_to_add(n.op(0)).seq.begin(), bitend = ex_to_add(n.op(0)).seq.end();
 			while (bit != bitend) {
-				o.push_back((new lst(recombine_pair_to_ex(*bit), n.op(1)))->setflag(status_flags::dynallocated));
+				nums.push_back(recombine_pair_to_ex(*bit));
+				dens.push_back(n.op(1));
 				bit++;
 			}
 
@@ -1935,53 +1938,40 @@ ex add::normal(lst &sym_lst, lst &repl_lst, int level) const
 			// split it into numerator and denominator
 			GINAC_ASSERT(ex_to_numeric(ex_to_add(n.op(0)).overall_coeff).is_rational());
 			numeric overall = ex_to_numeric(ex_to_add(n.op(0)).overall_coeff);
-			o.push_back((new lst(overall.numer(), overall.denom() * n.op(1)))->setflag(status_flags::dynallocated));
-		} else
-			o.push_back(n);
+			nums.push_back(overall.numer());
+			dens.push_back(overall.denom() * n.op(1));
+		} else {
+			nums.push_back(n.op(0));
+			dens.push_back(n.op(1));
+		}
 		it++;
 	}
-	o.push_back(overall_coeff.bp->normal(sym_lst, repl_lst, level-1));
+	ex n = overall_coeff.bp->normal(sym_lst, repl_lst, level-1);
+	nums.push_back(n.op(0));
+	dens.push_back(n.op(1));
+	GINAC_ASSERT(nums.size() == dens.size());
 
-	// o is now a vector of {numerator, denominator} lists
+	// Now, nums is a vector of all numerators and dens is a vector of
+	// all denominators
 
-	// Determine common denominator
-	ex den = _ex1();
-	exvector::const_iterator ait = o.begin(), aitend = o.end();
+	// Add fractions sequentially
+	exvector::const_iterator num_it = nums.begin(), num_itend = nums.end();
+	exvector::const_iterator den_it = dens.begin(), den_itend = dens.end();
 //std::clog << "add::normal uses the following summands:\n";
-	while (ait != aitend) {
-//std::clog << " num = " << ait->op(0) << ", den = " << ait->op(1) << endl;
-		den = lcm(ait->op(1), den, false);
-		ait++;
+//std::clog << " num = " << *num_it << ", den = " << *den_it << endl;
+	ex num = *num_it++, den = *den_it++;
+	while (num_it != num_itend) {
+//std::clog << " num = " << *num_it << ", den = " << *den_it << endl;
+		ex co_den1, co_den2;
+		ex g = gcd(den, *den_it, &co_den1, &co_den2, false);
+		num = (num * co_den2) + (*num_it * co_den1);
+		den *= co_den2;		// this is the lcm(den, *den_it)
+		num_it++; den_it++;
 	}
 //std::clog << " common denominator = " << den << endl;
 
-	// Add fractions
-	if (den.is_equal(_ex1())) {
-
-		// Common denominator is 1, simply add all fractions
-		exvector num_seq;
-		for (ait=o.begin(); ait!=aitend; ait++) {
-			num_seq.push_back(ait->op(0) / ait->op(1));
-		}
-		return (new lst((new add(num_seq))->setflag(status_flags::dynallocated), den))->setflag(status_flags::dynallocated);
-
-	} else {
-
-		// Perform fractional addition
-		exvector num_seq;
-		for (ait=o.begin(); ait!=aitend; ait++) {
-			ex q;
-			if (!divide(den, ait->op(1), q, false)) {
-				// should not happen
-				throw(std::runtime_error("invalid expression in add::normal, division failed"));
-			}
-			num_seq.push_back((ait->op(0) * q).expand());
-		}
-		ex num = (new add(num_seq))->setflag(status_flags::dynallocated);
-
-		// Cancel common factors from num/den
-		return frac_cancel(num, den);
-	}
+	// Cancel common factors from num/den
+	return frac_cancel(num, den);
 }