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SortUtils.js
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SortUtils.js
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// Hybrid radix sort from
// - https://gist.github.com/sciecode/93ed864dd77c5c8803c6a86698d68dab
// - https://github.com/mrdoob/three.js/pull/27202#issuecomment-1817640271
const POWER = 3;
const BIT_MAX = 32;
const BIN_BITS = 1 << POWER;
const BIN_SIZE = 1 << BIN_BITS;
const ITERATIONS = BIT_MAX / BIN_BITS;
const bins = new Array( ITERATIONS );
const caches = new Array( ITERATIONS );
const bins_buffer = new ArrayBuffer( 2 * ITERATIONS * BIN_SIZE * 4 );
let c = 0;
for ( let i = 0; i < ITERATIONS; i ++ ) {
bins[ i ] = new Uint32Array( bins_buffer, c, BIN_SIZE );
c += BIN_SIZE * 4;
caches[ i ] = new Uint32Array( bins_buffer, c, BIN_SIZE );
c += BIN_SIZE * 4;
}
const defaultGet = ( el ) => el;
export const radixSort = ( arr, opt ) => {
const len = arr.length;
const options = opt || {};
const aux = options.aux || new arr.constructor( len );
const get = options.get || defaultGet;
const data = [ arr, aux ];
let compare, accumulate, recurse;
if ( options.reversed ) {
compare = ( a, b ) => a < b;
accumulate = ( bin ) => {
for ( let j = BIN_SIZE - 2; j >= 0; j -- )
bin[ j ] += bin[ j + 1 ];
};
recurse = ( cache, depth, start ) => {
let prev = 0;
for ( let j = BIN_SIZE - 1; j >= 0; j -- ) {
const cur = cache[ j ], diff = cur - prev;
if ( diff != 0 ) {
if ( diff > 32 )
radixSortBlock( depth + 1, start + prev, diff );
else
insertionSortBlock( depth + 1, start + prev, diff );
prev = cur;
}
}
};
} else {
compare = ( a, b ) => a > b;
accumulate = ( bin ) => {
for ( let j = 1; j < BIN_SIZE; j ++ )
bin[ j ] += bin[ j - 1 ];
};
recurse = ( cache, depth, start ) => {
let prev = 0;
for ( let j = 0; j < BIN_SIZE; j ++ ) {
const cur = cache[ j ], diff = cur - prev;
if ( diff != 0 ) {
if ( diff > 32 )
radixSortBlock( depth + 1, start + prev, diff );
else
insertionSortBlock( depth + 1, start + prev, diff );
prev = cur;
}
}
};
}
const insertionSortBlock = ( depth, start, len ) => {
const a = data[ depth & 1 ];
const b = data[ ( depth + 1 ) & 1 ];
for ( let j = start + 1; j < start + len; j ++ ) {
const p = a[ j ], t = get( p );
let i = j;
while ( i > 0 ) {
if ( compare( get( a[ i - 1 ] ), t ) )
a[ i ] = a[ -- i ];
else
break;
}
a[ i ] = p;
}
if ( ( depth & 1 ) == 1 ) {
for ( let i = start; i < start + len; i ++ )
b[ i ] = a[ i ];
}
};
const radixSortBlock = ( depth, start, len ) => {
const a = data[ depth & 1 ];
const b = data[ ( depth + 1 ) & 1 ];
const shift = ( 3 - depth ) << POWER;
const end = start + len;
const bin = bins[ depth ];
const cache = caches[ depth ];
bin.fill( 0 );
for ( let j = start; j < end; j ++ )
bin[ ( get( a[ j ] ) >> shift ) & ( BIN_SIZE - 1 ) ] ++;
accumulate( bin );
cache.set( bin );
for ( let j = end - 1; j >= start; j -- )
b[ start + -- bin[ ( get( a[ j ] ) >> shift ) & ( BIN_SIZE - 1 ) ] ] = a[ j ];
if ( depth == ITERATIONS - 1 ) return;
recurse( cache, depth, start );
};
radixSortBlock( 0, 0, len );
};