From: Christian Bauer <Christian.Bauer@uni-mainz.de>
Date: Sat, 25 May 2002 18:39:43 +0000 (+0000)
Subject: added an additional dummy index symmetrization run over sums in
X-Git-Tag: release_1-0-9~5
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=ee1af48a44dbe1e3b743c3683cd3601deb7ce0ed;ds=inline

added an additional dummy index symmetrization run over sums in
simplify_indexed(), to find possible cancellations
---

diff --git a/check/exam_indexed.cpp b/check/exam_indexed.cpp
index a8c7cbd6..4d09bdff 100644
--- a/check/exam_indexed.cpp
+++ b/check/exam_indexed.cpp
@@ -155,7 +155,7 @@ static unsigned symmetry_check(void)
 	unsigned result = 0;
 
 	idx i(symbol("i"), 3), j(symbol("j"), 3), k(symbol("k"), 3), l(symbol("l"), 3);
-	symbol A("A"), B("B");
+	symbol A("A"), B("B"), C("C");
 	ex e;
 
 	result += check_equal(indexed(A, sy_symm(), i, j), indexed(A, sy_symm(), j, i));
@@ -187,6 +187,9 @@ static unsigned symmetry_check(void)
 	result += check_equal(symmetrize(e), 0);
 	result += check_equal(antisymmetrize(e), e);
 
+	e = (indexed(A, sy_anti(), i, j, k, l) * (indexed(B, j) * indexed(C, k) + indexed(B, k) * indexed(C, j)) + indexed(B, i, l)).expand();
+	result += check_equal_simplify(e, indexed(B, i, l));
+
 	return result;
 }
 
diff --git a/ginac/indexed.cpp b/ginac/indexed.cpp
index dcd6d951..dca12fd8 100644
--- a/ginac/indexed.cpp
+++ b/ginac/indexed.cpp
@@ -870,6 +870,27 @@ ex simplify_indexed(const ex & e, exvector & free_indices, exvector & dummy_indi
 			}
 		}
 
+		if (sum.is_zero()) {
+			free_indices.clear();
+			return sum;
+		}
+
+		// Symmetrizing over the dummy indices may cancel terms
+		int num_terms_orig = (is_a<add>(sum) ? sum.nops() : 1);
+		if (num_terms_orig > 1 && dummy_indices.size() >= 2) {
+			lst dummy_syms;
+			for (int i=0; i<dummy_indices.size(); i++)
+				dummy_syms.append(dummy_indices[i].op(0));
+			ex sum_symm = sum.symmetrize(dummy_syms);
+			if (sum_symm.is_zero()) {
+				free_indices.clear();
+				return _ex0;
+			}
+			int num_terms = (is_a<add>(sum_symm) ? sum_symm.nops() : 1);
+			if (num_terms < num_terms_orig)
+				return sum_symm;
+		}
+
 		return sum;
 	}