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Add strategy heuristics

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This commit is contained in:
Felix Hanau 2019-08-06 14:58:54 +01:00
parent 1ade19aebf
commit d286cf9eaf
1 changed files with 43 additions and 1 deletions
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44
src/lib.rs
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@ -540,6 +540,8 @@ fn optimize_png(
(*f, png.raw.filter_image(*f))
})
.collect();
//Use heuristics to choose the best filter strategy.
if opts.use_heuristics && filter.len() > 1 {
let best_size_heuristics = AtomicMin::new(None);
let mut heuristic_results: Vec<TrialOptions> = Vec::with_capacity(filter.len());
@ -575,7 +577,7 @@ fn optimize_png(
Some((trial.filter, new_size))
});
let best_filter = best_filter.reduce_with(|i, j| if i.1 <= j.1 {i} else {j});
let best_filter = best_filter.reduce_with(|i, j| if i.1 < j.1 || (i.1 == j.1 && i.0 < j.0) {i} else {j});
if let Some(result) = best_filter {
filter.clear();
@ -584,6 +586,46 @@ fn optimize_png(
}
}
//Use heuristics to choose whether to try strategy 0 or 1 at full compression. Compression
//level 5 gives a good approximation.
if opts.use_heuristics && strategies.len() == 4 {
let best_size_heuristics = AtomicMin::new(None);
let heuristic_results = vec![0, 1];
let strategy_heuristics_iter = heuristic_results.into_par_iter().with_max_len(1);
let best_strategy = strategy_heuristics_iter.filter_map(|strategy| {
if deadline.passed() {
return None;
}
let filtered = &filters[filter.iter().last().unwrap()];
let new_idat = deflate::deflate(
filtered,
5,
strategy,
opts.window,
&best_size_heuristics,
&deadline,
);
let new_size = match new_idat {
Ok(n) => n.len(),
_ => return None,
};
// update best size across all threads
best_size_heuristics.set_min(new_size);
Some((strategy, new_size))
});
let best_strategy = best_strategy.reduce_with(|i, j| if i.1 < j.1 || (i.1 == j.1 && i.0 < j.0) {i} else {j});
if let Some(result) = best_strategy {
strategies.clear();
strategies.insert(result.0);
strategies.insert(2);
strategies.insert(3);
}
}
// Go through selected permutations and determine the best
let combinations = if opts.deflate == Deflaters::Zlib && !deadline.passed() {
filter.len() * compression.len() * strategies.len()