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added missing headers for thiersort3

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Richard Thier 2025-09-29 18:21:16 +02:00
parent 7ca9a19c5d
commit a5cb0995e3
2 changed files with 245 additions and 0 deletions
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thiersort3.h Normal file
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#ifndef THIER_SORT3_H
#define THIER_SORT3_H
#include <stdint.h>
#include "threepass_xbit.h"
/* A non-implace tricky float-hackz based bucket sort variant. Uses threepass_xbit and removes some compies! */
/* Float and unsigned32 reinterpreter */
union th3_fu {
float f;
uint32_t u;
};
typedef union th3_fu th3_fu;
/** Tells from the key which bucket it is in. */
static inline uint32_t witch_bucket3(uint32_t key) {
/* This is hackz to misuse int->float converter HEAVILY and IEE for bucketing */
/* https://en.wikipedia.org/wiki/Single-precision_floating-point_format */
/* Old Hungarian ASM trick I know from Tomcat/Abaddon mailing list and prog.hu */
/* "A következő nagyon fontos gondolat, hogy két lebegőpontos számot, */
/* amennyiben pozitív, "simán" is összehasonlíthatunk" */
/* See: https://prog.hu/cikkek/100239/fpu-gems */
/* This approach uses 12 bits from a 32 bit float to map onto a byte bucket index */
th3_fu as;
as.f = (float) key;
uint32_t witch_base = (key <= 2) ? 0 : (as.u >> 23) - 128; // 0, [127..159] -> [0..31]
// return witch_base * 8 + ((as.u >> (23 - 3)) & 7); // 0..255
return witch_base * 128 + ((as.u >> (23 - 7)) & 127); // 0..2047
/* Alternative (but I measure it being worse):
return (as.u >> 23);
*/
}
/**
* Sort the array using the temporary array of the same size with fast bucket sort thiersort.
*
* @param arr The array to sort, will contain result afterwards
* @param temparr The temporary array with same size
* @param n Number of elements in arr and temparr
* @param rstate Create with sch_rand_state rstate = schwab_rand_state(junk_uint32_t);
*/
static inline void thiersort3(uint32_t *arr, uint32_t *temparr, int n) {
int bucket[4096]; /* Inclusive */
int bucket_end[4096]; /* Not inclusive */
/* Check if need to sort at all - needed for invariants later */
if(n < 2) {
return;
}
/* Count */
#pragma GCC unroll 64
for(int i = 0; i < 4096; ++i) {
bucket[i] = 0;
}
#pragma GCC unroll 64
for(int i = 0; i < n; ++i) {
++bucket[witch_bucket3(arr[i])];
}
/* Prefix sum (like in Magyarsort) */
uint32_t prev = 0;
#pragma GCC unroll 4
for (int i = 0; i < 4096; i++) {
bucket[i] += prev;
prev = bucket[i];
}
/* Save end-offsets */
#pragma GCC unroll 64
for(int i = 0; i < 4096; ++i) {
bucket_end[i] = bucket[i];
}
/* arr -> temparr */
/* Move to the buckets */
/* Rem.: This also changes bucket[i] so they will point to bucket beginnings */
#pragma GCC unroll 64
for(int i = 0; i < n; ++i) {
uint32_t num = arr[i];
uint32_t witch = witch_bucket3(num);
int offset = (--bucket[witch]);
temparr[offset] = num;
}
/* temparr -> arr each bucket and sort them in-place */
#pragma GCC unroll 64
for(int b = 0; b < 4096; ++b) {
int begin = bucket[b];
int end = bucket_end[b];
/* Ensure exists */
if(begin >= end) {
continue;
}
/* Use our specialized threepass */
/* - which does not use up all the bits */
/* - which does not allocate and copy back to arr here */
uint32_t n = end - begin;
uint32_t *a = &(temparr[begin]);
uint32_t *buf = &(arr[begin]);
threepass_xb(a, buf, n);
}
}
#endif /* THIER_SORT3_H */

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#ifndef THREE_PASS_XB_H
#define THREE_PASS_XB_H
/* Basically like threepass.h but but fewer bits - only for thiersort3! */
/* How the 28-30 bits gets separated? This is chosen because I saw that: */
/* - in float trickery I saw at around 4 billion the buckets change around 200 million */
/* - Which is smaller than 1/2 or 1/4 or 1/8 or 1/16 of it because 16*200 mil = 3.2 bill 28 bit is needed */
/* - This means those bits in numbers DO get used when we are running as internal sort of thier3 */
/* - But the numbers high bits (29..32th bits) stay the same inside each bucket so we spare it! */
/* - If you know your data does not have all the range of 32 bits you can #define these by #define CUSTOM_TPBX_BITS */
#ifndef CUSTOM_TPBX_BITS
#define TPBX1 10 // top
#define TPBX2 9 // mid
#define TPBX3 9 // bottom
#endif /* CUSTOM_TPBX_BITS */
static inline constexpr uint32_t min3u32_xb(uint32_t a, uint32_t b, uint32_t c) noexcept {
return (a <= b) ?
((a <= c) ? a : c) :
((b <= c) ? b : c);
}
/**
* Simple three-pass (ok: 3 + 1) bottom-up internal radix sort writter for thiersort3
*
* @param a The array to sort - will be changed too!
* @param buf Result array with the same size - result will be here
* @param n The number of elements
*/
static inline void threepass_xb(uint32_t *a, uint32_t *buf, int n) noexcept {
assert(buf != NULL);
constexpr int shr1 = TPBX3 + TPBX2;
constexpr int shr2 = TPBX3;
constexpr int shr3 = 0;
constexpr int mask1 = (1 << TPBX1) - 1;
constexpr int mask2 = (1 << TPBX2) - 1;
constexpr int mask3 = (1 << TPBX3) - 1;
/* helper buffers. */
int sz = n * sizeof(a[0]);
static thread_local uint32_t bucket1[1 << TPBX1];
memset(bucket1, 0, (1 << TPBX1) * sizeof(uint32_t));
static thread_local uint32_t bucket2[1 << TPBX2];
memset(bucket2, 0, (1 << TPBX2) * sizeof(uint32_t));
static thread_local uint32_t bucket3[1 << TPBX3];
memset(bucket3, 0, (1 << TPBX3) * sizeof(uint32_t));
/* Count occurences (can count together with good ILP) */
#pragma GCC unroll 64
for(uint32_t i = 0; i < n; ++i) {
++bucket1[(a[i] >> shr1) & mask1];
++bucket2[(a[i] >> shr2) & mask2];
++bucket3[(a[i] >> shr3) & mask3];
}
/* Count prefix sums - try as much ILP as possible because bigger arrays than usual! */
uint32_t prev1 = 0;
uint32_t prev2 = 0;
uint32_t prev3 = 0;
uint32_t common = min3u32_xb(
(1 << TPBX1),
(1 << TPBX2),
(1 << TPBX3)
);
int i = 0;
#pragma GCC unroll 8
for (; i < common; ++i) {
bucket1[i] += prev1;
prev1 = bucket1[i];
bucket2[i] += prev2;
prev2 = bucket2[i];
bucket3[i] += prev3;
prev3 = bucket3[i];
}
/* Do remaining 1 */
for (int j = i; j < (1 << TPBX1); ++j) {
bucket1[j] += prev1;
prev1 = bucket1[j];
}
/* Do remaining 2 */
for (int j = i; j< (1 << TPBX2); ++j) {
bucket2[j] += prev2;
prev2 = bucket2[j];
}
/* Do remaining 3 */
for (int j = i; j < (1 << TPBX3); ++j) {
bucket3[j] += prev3;
prev3 = bucket3[j];
}
// Bottom digit a->buf
// right-to-left to ensure already sorted digits order we keep for iterations
#pragma GCC unroll 48
for(uint32_t i = n; i > 0; --i) {
// Prefetch caches
//__builtin_prefetch(&a[i-8]);
// Get num and its new offset / location
auto num = a[i - 1];
auto bkeyni = (num >> shr3) & mask3;
auto offset = --bucket3[bkeyni];
// Add to the proper target location
buf[offset] = num;
}
// Mid digit buf->a
// right-to-left to ensure already sorted digits order we keep for iterations
#pragma GCC unroll 48
for(uint32_t i = n; i > 0; --i) {
// Prefetch caches
//__builtin_prefetch(&buf[i-8]);
// Get num and its new offset / location
auto num = buf[i - 1];
auto bkeyni = (num >> shr2) & mask2;
auto offset = --bucket2[bkeyni];
// Add to the proper target location
a[offset] = num;
}
// Top digit a->buf
// right-to-left to ensure already sorted digits order we keep for iterations
#pragma GCC unroll 48
for(uint32_t i = n; i > 0; --i) {
// Prefetch caches
// __builtin_prefetch(&a[i-16]);
// Get num and its new offset / location
auto num = a[i - 1];
auto bkeyni = (num >> shr1) & mask1;
auto offset = --bucket1[bkeyni];
// Add to the proper target location
buf[offset] = num;
}
}
#endif /* THREE_PASS_XB_H */