mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-11-01 00:11:00 +00:00
1d16fdecd6
No functionality change. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206740 91177308-0d34-0410-b5e6-96231b3b80d8
103 lines
3.4 KiB
C++
103 lines
3.4 KiB
C++
//===-- llvm/ADT/edit_distance.h - Array edit distance function --- C++ -*-===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file defines a Levenshtein distance function that works for any two
|
|
// sequences, with each element of each sequence being analogous to a character
|
|
// in a string.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#ifndef LLVM_ADT_EDIT_DISTANCE_H
|
|
#define LLVM_ADT_EDIT_DISTANCE_H
|
|
|
|
#include "llvm/ADT/ArrayRef.h"
|
|
#include <algorithm>
|
|
#include <memory>
|
|
|
|
namespace llvm {
|
|
|
|
/// \brief Determine the edit distance between two sequences.
|
|
///
|
|
/// \param FromArray the first sequence to compare.
|
|
///
|
|
/// \param ToArray the second sequence to compare.
|
|
///
|
|
/// \param AllowReplacements whether to allow element replacements (change one
|
|
/// element into another) as a single operation, rather than as two operations
|
|
/// (an insertion and a removal).
|
|
///
|
|
/// \param MaxEditDistance If non-zero, the maximum edit distance that this
|
|
/// routine is allowed to compute. If the edit distance will exceed that
|
|
/// maximum, returns \c MaxEditDistance+1.
|
|
///
|
|
/// \returns the minimum number of element insertions, removals, or (if
|
|
/// \p AllowReplacements is \c true) replacements needed to transform one of
|
|
/// the given sequences into the other. If zero, the sequences are identical.
|
|
template<typename T>
|
|
unsigned ComputeEditDistance(ArrayRef<T> FromArray, ArrayRef<T> ToArray,
|
|
bool AllowReplacements = true,
|
|
unsigned MaxEditDistance = 0) {
|
|
// The algorithm implemented below is the "classic"
|
|
// dynamic-programming algorithm for computing the Levenshtein
|
|
// distance, which is described here:
|
|
//
|
|
// http://en.wikipedia.org/wiki/Levenshtein_distance
|
|
//
|
|
// Although the algorithm is typically described using an m x n
|
|
// array, only two rows are used at a time, so this implemenation
|
|
// just keeps two separate vectors for those two rows.
|
|
typename ArrayRef<T>::size_type m = FromArray.size();
|
|
typename ArrayRef<T>::size_type n = ToArray.size();
|
|
|
|
const unsigned SmallBufferSize = 64;
|
|
unsigned SmallBuffer[SmallBufferSize];
|
|
std::unique_ptr<unsigned[]> Allocated;
|
|
unsigned *Previous = SmallBuffer;
|
|
if (2*(n + 1) > SmallBufferSize) {
|
|
Previous = new unsigned [2*(n+1)];
|
|
Allocated.reset(Previous);
|
|
}
|
|
unsigned *Current = Previous + (n + 1);
|
|
|
|
for (unsigned i = 0; i <= n; ++i)
|
|
Previous[i] = i;
|
|
|
|
for (typename ArrayRef<T>::size_type y = 1; y <= m; ++y) {
|
|
Current[0] = y;
|
|
unsigned BestThisRow = Current[0];
|
|
|
|
for (typename ArrayRef<T>::size_type x = 1; x <= n; ++x) {
|
|
if (AllowReplacements) {
|
|
Current[x] = std::min(
|
|
Previous[x-1] + (FromArray[y-1] == ToArray[x-1] ? 0u : 1u),
|
|
std::min(Current[x-1], Previous[x])+1);
|
|
}
|
|
else {
|
|
if (FromArray[y-1] == ToArray[x-1]) Current[x] = Previous[x-1];
|
|
else Current[x] = std::min(Current[x-1], Previous[x]) + 1;
|
|
}
|
|
BestThisRow = std::min(BestThisRow, Current[x]);
|
|
}
|
|
|
|
if (MaxEditDistance && BestThisRow > MaxEditDistance)
|
|
return MaxEditDistance + 1;
|
|
|
|
unsigned *tmp = Current;
|
|
Current = Previous;
|
|
Previous = tmp;
|
|
}
|
|
|
|
unsigned Result = Previous[n];
|
|
return Result;
|
|
}
|
|
|
|
} // End llvm namespace
|
|
|
|
#endif
|