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optimize fallback_sort #113

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Merged
folkertdev merged 4 commits into from
Jun 16, 2025
Merged

optimize fallback_sort #113

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e16a461
general cleanup
folkertdev Jun 16, 2025
9cce235
do not use `Ord::cmp`; it is slower than an if-else sequence
folkertdev Jun 16, 2025
50f7982
cleanup
folkertdev Jun 16, 2025
6680435
refactor loop
folkertdev Jun 16, 2025
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69 changes: 32 additions & 37 deletions libbz2-rs-sys/src/blocksort.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -125,30 +125,32 @@ fn fallbackQSort3(fmap: &mut [u32], eclass: &[u32], loSt: i32, hiSt: i32) {

loop {
while unLo <= unHi {
match eclass[fmap[unLo as usize] as usize].cmp(&med) {
Ordering::Greater => break,
Ordering::Equal => {
fmap.swap(unLo as usize, ltLo as usize);
ltLo += 1;
unLo += 1;
}
Ordering::Less => {
unLo += 1;
}
let a = eclass[fmap[unLo as usize] as usize];
let b = med;

if a > b {
break;
} else if a == b {
fmap.swap(unLo as usize, ltLo as usize);
ltLo += 1;
unLo += 1;
} else {
unLo += 1;
}
}

while unLo <= unHi {
match eclass[fmap[unHi as usize] as usize].cmp(&med) {
Ordering::Less => break,
Ordering::Equal => {
fmap.swap(unHi as usize, gtHi as usize);
gtHi -= 1;
unHi -= 1;
}
Ordering::Greater => {
unHi -= 1;
}
let a = eclass[fmap[unHi as usize] as usize];
let b = med;

if a < b {
break;
} else if a == b {
fmap.swap(unHi as usize, gtHi as usize);
gtHi -= 1;
unHi -= 1;
} else {
unHi -= 1;
}
}

Expand Down Expand Up @@ -225,14 +227,8 @@ fn fallbackSort(
let mut ftab: [i32; 257] = [0; 257];
let mut ftabCopy: [i32; 256] = [0; 256];
let mut H: i32;
let mut i: i32;
let mut j: i32;
let mut k: i32;
let mut l: i32;
let mut r: i32;
let mut cc: i32;
let mut cc1: i32;
let mut nNotDone: i32;

/*--
Initial 1-char radix sort to generate
Expand Down Expand Up @@ -287,21 +283,20 @@ fn fallbackSort(
if verb >= 4 {
debug_log!(" depth {:>6} has ", H);
}
j = 0;
i = 0;
while i < nblock {
let mut j = 0;
for (i, x) in fmap[..nblock as usize].iter().enumerate() {
if ISSET_BH!(i) {
j = i;
}
k = fmap[i as usize].wrapping_sub(H as c_uint) as i32;
k = x.wrapping_sub(H as c_uint) as i32;
if k < 0 {
k += nblock;
}
arr2.eclass()[k as usize] = j as u32;
i += 1;
}
nNotDone = 0;
r = -1;

let mut nNotDone = 0;
let mut r = -1;
loop {
/*-- find the next non-singleton bucket --*/
k = r + 1;
Expand Down Expand Up @@ -342,11 +337,11 @@ fn fallbackSort(
fallbackQSort3(fmap, arr2.eclass(), l, r);

/*-- scan bucket and generate header bits-- */
cc = -1;
for i in l..=r {
cc1 = arr2.eclass()[fmap[i as usize] as usize] as i32;
let mut cc = -1;
for (i, x) in fmap[l as usize..=r as usize].iter().enumerate() {
let cc1 = arr2.eclass()[*x as usize] as i32;
if cc != cc1 {
SET_BH!(i);
SET_BH!(l + i as i32);
cc = cc1;
}
}
Expand Down
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