From: Jens Vollinga <jensv@nikhef.nl>
Date: Thu, 19 May 2011 07:44:11 +0000 (+0200)
Subject: The patch improves the run time at the expense of using more RAM in some
X-Git-Tag: release_1-6-0~12
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=ab1aedf73a5d062bf50ed1e740f38a4503d7fead

The patch improves the run time at the expense of using more RAM in some
situations. Please note: it doesn't improve the actual algorithm
(iteration over all permutations). Thanks to Alexei Sheplyakov.
---

diff --git a/ginac/symmetry.cpp b/ginac/symmetry.cpp
index 7d1ff978..d93e34cb 100644
--- a/ginac/symmetry.cpp
+++ b/ginac/symmetry.cpp
@@ -22,6 +22,7 @@
 
 #include "symmetry.h"
 #include "lst.h"
+#include "add.h"
 #include "numeric.h" // for factorial()
 #include "operators.h"
 #include "archive.h"
@@ -495,7 +496,8 @@ static ex symm(const ex & e, exvector::const_iterator first, exvector::const_ite
 
 	// Loop over all permutations (the first permutation, which is the
 	// identity, is unrolled)
-	ex sum = e;
+	exvector sum_v;
+	sum_v.push_back(e);
 	while (std::next_permutation(iv, iv + num)) {
 		lst new_lst;
 		for (unsigned i=0; i<num; i++)
@@ -505,8 +507,9 @@ static ex symm(const ex & e, exvector::const_iterator first, exvector::const_ite
 			memcpy(iv2, iv, num * sizeof(unsigned));
 			term *= permutation_sign(iv2, iv2 + num);
 		}
-		sum += term;
+		sum_v.push_back(term);
 	}
+	ex sum = (new add(sum_v))->setflag(status_flags::dynallocated);
 
 	delete[] iv;
 	delete[] iv2;