forked from mirrors/jj
1e657c5331
The current diff algorithm does a full LCS on the words of the texts, which is really slow. Diffing the working copy when e.g. `src/commands.py` has changes far apart takes seconds. This patch adds an implementation inspired by JGit's Histogram diff. I say "inspired" because I just didn't quite understand it :P In particular, I didn't understand what it does when it finds non-unique elements. I decided to line up the leading common elements on both sides of the merge. I don't know if that usually gives good enough results in practice. I'm sure this can still be optimized a lot, but this seems good enough as a start. There is also many things to improve about the quality of the diffs.
71 lines
1.9 KiB
Rust
71 lines
1.9 KiB
Rust
#![feature(test)]
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extern crate test;
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use jujube_lib::diff;
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use test::Bencher;
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fn unchanged_lines(count: usize) -> (String, String) {
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let mut lines = vec![];
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for i in 0..count {
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lines.push(format!("left line {}\n", i));
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}
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(lines.join(""), lines.join(""))
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}
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fn modified_lines(count: usize) -> (String, String) {
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let mut left_lines = vec![];
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let mut right_lines = vec![];
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for i in 0..count {
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left_lines.push(format!("left line {}\n", i));
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right_lines.push(format!("right line {}\n", i));
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}
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(left_lines.join(""), right_lines.join(""))
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}
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fn reversed_lines(count: usize) -> (String, String) {
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let mut left_lines = vec![];
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for i in 0..count {
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left_lines.push(format!("left line {}\n", i));
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}
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let mut right_lines = left_lines.clone();
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right_lines.reverse();
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(left_lines.join(""), right_lines.join(""))
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}
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#[bench]
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fn bench_diff_1k_unchanged_lines(b: &mut Bencher) {
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let (left, right) = unchanged_lines(1000);
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b.iter(|| diff::diff(left.as_bytes(), right.as_bytes()));
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}
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#[bench]
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fn bench_diff_10k_unchanged_lines(b: &mut Bencher) {
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let (left, right) = unchanged_lines(10000);
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b.iter(|| diff::diff(left.as_bytes(), right.as_bytes()));
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}
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#[bench]
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fn bench_diff_1k_modified_lines(b: &mut Bencher) {
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let (left, right) = modified_lines(1000);
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b.iter(|| diff::diff(left.as_bytes(), right.as_bytes()));
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}
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#[bench]
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fn bench_diff_10k_modified_lines(b: &mut Bencher) {
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let (left, right) = modified_lines(10000);
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b.iter(|| diff::diff(left.as_bytes(), right.as_bytes()));
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}
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#[bench]
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fn bench_diff_1k_lines_reversed(b: &mut Bencher) {
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let (left, right) = reversed_lines(1000);
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b.iter(|| diff::diff(left.as_bytes(), right.as_bytes()));
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}
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#[bench]
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fn bench_diff_10k_lines_reversed(b: &mut Bencher) {
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let (left, right) = reversed_lines(10000);
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b.iter(|| diff::diff(left.as_bytes(), right.as_bytes()));
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}
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