From 74a2124f6ebd6529fa31eafcfa5fe56b708dfcd6 Mon Sep 17 00:00:00 2001
From: Matthias Diener <mdiener@illinois.edu>
Date: Thu, 12 May 2022 14:17:10 -0500
Subject: [PATCH] add get_num_nodes() (#98)
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* add get_num_nodes()

* doc improvements

* doc and test improvements

* doc fixes

* update copyright year

Co-authored-by: Andreas Klöckner <inform@tiker.net>
---
 doc/mappers.rst             |  6 ++++
 pymbolic/mapper/analysis.py | 64 +++++++++++++++++++++++++++++++++++++
 test/test_pymbolic.py       | 17 ++++++++++
 3 files changed, 87 insertions(+)
 create mode 100644 pymbolic/mapper/analysis.py

diff --git a/doc/mappers.rst b/doc/mappers.rst
index 93d39b4..4a92531 100644
--- a/doc/mappers.rst
+++ b/doc/mappers.rst
@@ -39,4 +39,10 @@ Finding expression properties
 .. autoclass:: FlopCounter
 .. autoclass:: CSEAwareFlopCounter
 
+Analysis tools
+^^^^^^^^^^^^^^
+
+.. automodule:: pymbolic.mapper.analysis
+
+
 .. vim: sw=4
diff --git a/pymbolic/mapper/analysis.py b/pymbolic/mapper/analysis.py
new file mode 100644
index 0000000..633c034
--- /dev/null
+++ b/pymbolic/mapper/analysis.py
@@ -0,0 +1,64 @@
+__copyright__ = """Copyright (C) 2022 University of Illinois Board of Trustees"""
+
+__license__ = """
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+"""
+
+
+from pymbolic.mapper import CachedWalkMapper
+
+
+__doc__ = """
+.. autoclass:: NodeCountMapper
+.. autofunction:: get_num_nodes
+"""
+
+
+# {{{ NodeCountMapper
+
+class NodeCountMapper(CachedWalkMapper):
+    """
+    Counts the number of nodes in an expression tree. Nodes that occur
+    repeatedly as well as :class:`~pymbolic.primitives.CommonSubexpression`
+    nodes are only counted once.
+
+    .. attribute:: count
+
+       The number of nodes.
+    """
+
+    def __init__(self) -> None:
+        super().__init__()
+        self.count = 0
+
+    def post_visit(self, expr) -> None:
+        self.count += 1
+
+
+def get_num_nodes(expr) -> int:
+    """Returns the number of nodes in *expr*. Nodes that occur
+    repeatedly as well as :class:`~pymbolic.primitives.CommonSubexpression`
+    nodes are only counted once."""
+
+    ncm = NodeCountMapper()
+    ncm(expr)
+
+    return ncm.count
+
+# }}}
diff --git a/test/test_pymbolic.py b/test/test_pymbolic.py
index 08a9d81..d30dbdb 100644
--- a/test/test_pymbolic.py
+++ b/test/test_pymbolic.py
@@ -938,6 +938,23 @@ def test_cached_mapper_differentiates_float_int():
 # }}}
 
 
+def test_nodecount():
+    from pymbolic.mapper.analysis import get_num_nodes
+    expr = prim.Sum((4, 4.0))
+
+    assert get_num_nodes(expr) == 3
+
+    x = prim.Variable("x")
+    y = prim.Variable("y")
+    z = prim.Variable("z")
+
+    subexpr = prim.CommonSubexpression(4 * (x**2 + y + z))
+    expr = 3*subexpr + subexpr + subexpr + subexpr
+    expr = expr + expr + expr
+
+    assert get_num_nodes(expr) == 12
+
+
 if __name__ == "__main__":
     import sys
     if len(sys.argv) > 1:
-- 
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