From c5fc2e38c1361aef5820f91a4b1d0375e97f3af9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Villemot?= <sebastien@dynare.org>
Date: Mon, 28 Jan 2019 15:15:58 +0100
Subject: [PATCH] Simplify log(1/x) into -log(x) (and similarly for log10)
---
src/DataTree.cc | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 deletions(-)
diff --git a/src/DataTree.cc b/src/DataTree.cc
index 0e3c22b7..7a60c67d 100644
--- a/src/DataTree.cc
+++ b/src/DataTree.cc
@@ -357,29 +357,41 @@ DataTree::AddExp(expr_t iArg1)
expr_t
DataTree::AddLog(expr_t iArg1)
{
- if (iArg1 != Zero && iArg1 != One)
- return AddUnaryOp(UnaryOpcode::log, iArg1);
- else if (iArg1 == One)
+ if (iArg1 == One)
return Zero;
- else
+
+ if (iArg1 == Zero)
{
cerr << "ERROR: log(0) not defined!" << endl;
exit(EXIT_FAILURE);
}
+
+ // Try to simplify log(1/x) into -log(x)
+ auto barg1 = dynamic_cast<BinaryOpNode *>(iArg1);
+ if (barg1 && barg1->op_code == BinaryOpcode::divide && barg1->arg1 == One)
+ return AddUMinus(AddLog(barg1->arg2));
+
+ return AddUnaryOp(UnaryOpcode::log, iArg1);
}
expr_t
DataTree::AddLog10(expr_t iArg1)
{
- if (iArg1 != Zero && iArg1 != One)
- return AddUnaryOp(UnaryOpcode::log10, iArg1);
- else if (iArg1 == One)
+ if (iArg1 == One)
return Zero;
- else
+
+ if (iArg1 == Zero)
{
cerr << "ERROR: log10(0) not defined!" << endl;
exit(EXIT_FAILURE);
}
+
+ // Try to simplify log10(1/x) into -log10(x)
+ auto barg1 = dynamic_cast<BinaryOpNode *>(iArg1);
+ if (barg1 && barg1->op_code == BinaryOpcode::divide && barg1->arg1 == One)
+ return AddUMinus(AddLog10(barg1->arg2));
+
+ return AddUnaryOp(UnaryOpcode::log10, iArg1);
}
expr_t
--
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