| commit | 6df6eee46320bd774019d8512e765ee60cea5519 | [log] [tgz] |
|---|---|---|
| author | Alan Donovan <adonovan@google.com> | Sun Oct 30 17:24:53 2022 -0400 |
| committer | Alan Donovan <adonovan@google.com> | Mon Dec 19 23:49:02 2022 +0000 |
| tree | 19d4162f642d804ede93bf37f01ad9dabed72940 | |
| parent | 57b126584613a4ac99e27138377d056bbaeed3d7 [diff] |
internal/diff/lcs: optimize inner loop
The core operation of the diff algorithm is to advance
a cursor forwards or backwards over common substrings
of the two sequences. This change refactors the sequence
abstraction to express this, permitting faster and type-
specialized implementations of the common-prefix and
common-suffix operations.
This improves the running time on the new LargeFileSmallDiff
benchmark by 17%:
Before:
BenchmarkLargeFileSmallDiff/bytes-8 9838 521006 ns/op
BenchmarkLargeFileSmallDiff/runes-8 10000 522915 ns/op
After:
BenchmarkLargeFileSmallDiff/string-8 14545 412497 ns/op
BenchmarkLargeFileSmallDiff/bytes-8 13868 432577 ns/op (-17%)
BenchmarkLargeFileSmallDiff/runes-8 13744 436548 ns/op (-17%)
Also, some cleanups:
- Compute is replaced by three Diff{Strings,Bytes,Runes} functions.
- The LCS result is now internal, as it is needed only by tests.
- The caller's maxDiff constant is moved into this package.
- Test{Forward,Backward,TwoSided} are factored together.
- Delete unused randlines().
- {append,prepend}lcs are now methods
- Diff declaration moved to more prominent location.
- A test of the three DiffT functions.
Future work:
- faster common-prefix implementations are possible: the two
operations still account for about 5% of this benchmark.
- common-suffix for strings is about 50% faster than for bytes.
Find out why.
- There appear to be opportunities for much bigger gains
on the above benchmark by stripping the common prefix and
suffix as a first step. See comments in benchmark.
Change-Id: I475b7fc731d628d54e652a4ace7ce67c6c2755c2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/446575
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Peter Weinberger <pjw@google.com>
Run-TryBot: Alan Donovan <adonovan@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
This repository provides the golang.org/x/tools module, comprising various tools and packages mostly for static analysis of Go programs, some of which are listed below. Use the “Go reference” link above for more information about any package.
It also contains the golang.org/x/tools/gopls module, whose root package is a language-server protocol (LSP) server for Go. An LSP server analyses the source code of a project and responds to requests from a wide range of editors such as VSCode and Vim, allowing them to support IDE-like functionality.
Selected commands:
cmd/goimports formats a Go program like go fmt and additionally inserts import statements for any packages required by the file after it is edited.cmd/callgraph prints the call graph of a Go program.cmd/digraph is a utility for manipulating directed graphs in textual notation.cmd/stringer generates declarations (including a String method) for “enum” types.cmd/toolstash is a utility to simplify working with multiple versions of the Go toolchain.These commands may be fetched with a command such as
go install golang.org/x/tools/cmd/goimports@latest
Selected packages:
go/ssa provides a static single-assignment form (SSA) intermediate representation (IR) for Go programs, similar to a typical compiler, for use by analysis tools.
go/packages provides a simple interface for loading, parsing, and type checking a complete Go program from source code.
go/analysis provides a framework for modular static analysis of Go programs.
go/callgraph provides call graphs of Go programs using a variety of algorithms with different trade-offs.
go/ast/inspector provides an optimized means of traversing a Go parse tree for use in analysis tools.
go/cfg provides a simple control-flow graph (CFG) for a Go function.
go/expect reads Go source files used as test inputs and interprets special comments within them as queries or assertions for testing.
go/gcexportdata and go/gccgoexportdata read and write the binary files containing type information used by the standard and gccgo compilers.
go/types/objectpath provides a stable naming scheme for named entities (“objects”) in the go/types API.
Numerous other packages provide more esoteric functionality.
This repository uses Gerrit for code changes. To learn how to submit changes, see https://golang.org/doc/contribute.html.
The main issue tracker for the tools repository is located at https://github.com/golang/go/issues. Prefix your issue with “x/tools/(your subdir):” in the subject line, so it is easy to find.
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It is encouraged that all JS and CSS code be run through this before submitting a change. However, it is not a strict requirement enforced by CI.