From d747b53a8b106d8f7c50442c0dff589d7ac1b613 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Villemot?= <sebastien@dynare.org>
Date: Thu, 12 Dec 2019 13:06:50 +0100
Subject: [PATCH] Simplify x*y/y in x
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Note that this actually corresponds to 4 different abstract syntax trees:
— (x*y)/y
— (y*x)/y
— (x/y)*y
— y*(x/y)
---
src/DataTree.cc | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/src/DataTree.cc b/src/DataTree.cc
index 3574b557..1887d627 100644
--- a/src/DataTree.cc
+++ b/src/DataTree.cc
@@ -243,6 +243,16 @@ DataTree::AddTimes(expr_t iArg1, expr_t iArg2)
return AddUMinus(iArg1);
else if (iArg1 != Zero && iArg1 != One && iArg2 != Zero && iArg2 != One)
{
+ // Simplify (x/y)*y in x
+ if (auto barg1 = dynamic_cast<BinaryOpNode *>(iArg1);
+ barg1 && barg1->op_code == BinaryOpcode::divide && barg1->arg2 == iArg2)
+ return barg1->arg1;
+
+ // Simplify y*(x/y) in x
+ if (auto barg2 = dynamic_cast<BinaryOpNode *>(iArg2);
+ barg2 && barg2->op_code == BinaryOpcode::divide && barg2->arg2 == iArg1)
+ return barg2->arg1;
+
// To treat commutativity of "*"
// Nodes iArg1 and iArg2 are sorted by index
if (iArg1->idx > iArg2->idx)
@@ -283,6 +293,16 @@ DataTree::AddDivide(expr_t iArg1, expr_t iArg2) noexcept(false)
barg2 && barg2->op_code == BinaryOpcode::divide && barg2->arg1 == One)
return AddTimes(iArg1, barg2->arg2);
+ // Simplify (x*y)/y and (y*x)/y in x
+ if (auto barg1 = dynamic_cast<BinaryOpNode *>(iArg1);
+ barg1 && barg1->op_code == BinaryOpcode::times)
+ {
+ if (barg1->arg2 == iArg2)
+ return barg1->arg1;
+ if (barg1->arg1 == iArg2)
+ return barg1->arg2;
+ }
+
return AddBinaryOp(iArg1, BinaryOpcode::divide, iArg2);
}
--
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