[PATCH] D127070: [ADT][NFC] Early bail out for ComputeEditDistance

[Nathan James via Phabricator via llvm-commits]

njames93 updated this revision to Diff 434755.
njames93 added a comment.
Herald added a subscriber: mgorny.

Add tests to verify bailing out.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D127070/new/

https://reviews.llvm.org/D127070

Files:
  llvm/include/llvm/ADT/edit_distance.h
  llvm/unittests/ADT/CMakeLists.txt
  llvm/unittests/ADT/EditDistanceTest.cpp


Index: llvm/unittests/ADT/EditDistanceTest.cpp
===================================================================
--- /dev/null
+++ llvm/unittests/ADT/EditDistanceTest.cpp
@@ -0,0 +1,60 @@
+//===- llvm/unittest/Support/EditDistanceTest.cpp - Edit distance tests ---===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/edit_distance.h"
+#include "gtest/gtest.h"
+#include <cstdlib>
+
+using namespace llvm;
+
+struct Result {
+  unsigned NumMaps;
+  unsigned EditDist;
+};
+
+Result editDistanceAndMaps(StringRef A, StringRef B,
+                           unsigned MaxEditDistance = 0) {
+  unsigned NumMaps = 0;
+  auto TrackMaps = [&](const char X) {
+    ++NumMaps;
+    return X;
+  };
+  auto EditDist = llvm::ComputeMappedEditDistance(
+      makeArrayRef(A.data(), A.size()), makeArrayRef(B.data(), B.size()),
+      TrackMaps, true, MaxEditDistance);
+  return {NumMaps, EditDist};
+}
+
+TEST(EditDistance, VerifyShortCircuit) {
+  StringRef Hello("Hello");
+  StringRef HelloWorld("HelloWorld");
+  Result R = editDistanceAndMaps(Hello, HelloWorld, 5);
+  EXPECT_EQ(R.EditDist, 5U);
+  EXPECT_GT(R.NumMaps, 0U);
+
+  R = editDistanceAndMaps(Hello, HelloWorld);
+  EXPECT_EQ(R.EditDist, 5U);
+  EXPECT_GT(R.NumMaps, 0U);
+
+  R = editDistanceAndMaps(Hello, HelloWorld, 4);
+  EXPECT_EQ(R.EditDist, 5U);
+  EXPECT_EQ(R.NumMaps, 0U);
+
+  R = editDistanceAndMaps(HelloWorld, Hello, 4);
+  EXPECT_EQ(R.EditDist, 5U);
+  EXPECT_EQ(R.NumMaps, 0U);
+
+  R = editDistanceAndMaps(Hello, HelloWorld, 1);
+  EXPECT_EQ(R.EditDist, 2U);
+  EXPECT_EQ(R.NumMaps, 0U);
+
+  R = editDistanceAndMaps(HelloWorld, Hello, 1);
+  EXPECT_EQ(R.EditDist, 2U);
+  EXPECT_EQ(R.NumMaps, 0U);
+}
Index: llvm/unittests/ADT/CMakeLists.txt
===================================================================
--- llvm/unittests/ADT/CMakeLists.txt
+++ llvm/unittests/ADT/CMakeLists.txt
@@ -22,6 +22,7 @@
   DenseSetTest.cpp
   DepthFirstIteratorTest.cpp
   DirectedGraphTest.cpp
+  EditDistanceTest.cpp
   EnumeratedArrayTest.cpp
   EquivalenceClassesTest.cpp
   FallibleIteratorTest.cpp
Index: llvm/include/llvm/ADT/edit_distance.h
===================================================================
--- llvm/include/llvm/ADT/edit_distance.h
+++ llvm/include/llvm/ADT/edit_distance.h
@@ -61,6 +61,15 @@
   typename ArrayRef<T>::size_type m = FromArray.size();
   typename ArrayRef<T>::size_type n = ToArray.size();
 
+  if (MaxEditDistance) {
+    // If the difference in size between the 2 arrays is larger than the max
+    // distance allowed, we can bail out as we will always need at least
+    // MaxEditDistance insertions or removals.
+    typename ArrayRef<T>::size_type AbsDiff = m > n ? m - n : n - m;
+    if (AbsDiff > MaxEditDistance)
+      return MaxEditDistance + 1;
+  }
+
   const unsigned SmallBufferSize = 64;
   unsigned SmallBuffer[SmallBufferSize];
   std::unique_ptr<unsigned[]> Allocated;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D127070.434755.patch
Type: text/x-patch
Size: 3194 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20220607/629d0edb/attachment.bin>