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512-bucketed thiersort2

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This commit is contained in:
Richard Thier 2025-09-27 01:24:18 +02:00
parent 5fc08c6fae
commit dcef96fee8
2 changed files with 25 additions and 18 deletions
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35
thiersort2.h
View File

@ -41,7 +41,8 @@ static inline uint32_t witch_bucket(uint32_t key) {
as.f = (float) key; as.f = (float) key;
uint32_t witch_base = (key <= 2) ? 0 : (as.u >> 23) - 128; // 0, [127..159] -> [0..31] 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); // return witch_base * 8 + ((as.u >> (23 - 3)) & 7); // 0..255
return witch_base * 16 + ((as.u >> (23 - 4)) & 15); // 0..255
/* Alternative (but I measure it being worse): /* Alternative (but I measure it being worse):
return (as.u >> 23); return (as.u >> 23);
*/ */
@ -56,8 +57,8 @@ static inline uint32_t witch_bucket(uint32_t key) {
* @param rstate Create with sch_rand_state rstate = schwab_rand_state(junk_uint32_t); * @param rstate Create with sch_rand_state rstate = schwab_rand_state(junk_uint32_t);
*/ */
static inline void thiersort2(uint32_t *arr, uint32_t *temparr, int n, sch_rand_state *rstate) { static inline void thiersort2(uint32_t *arr, uint32_t *temparr, int n, sch_rand_state *rstate) {
int bucket[256]; /* Inclusive */ int bucket[512]; /* Inclusive */
int bucket_end[256]; /* Not inclusive */ int bucket_end[512]; /* Not inclusive */
/* Check if need to sort at all - needed for invariants later */ /* Check if need to sort at all - needed for invariants later */
if(n < 2) { if(n < 2) {
@ -66,7 +67,7 @@ static inline void thiersort2(uint32_t *arr, uint32_t *temparr, int n, sch_rand_
/* Count */ /* Count */
#pragma GCC unroll 64 #pragma GCC unroll 64
for(int i = 0; i < 256; ++i) { for(int i = 0; i < 512; ++i) {
bucket[i] = 0; bucket[i] = 0;
} }
#pragma GCC unroll 64 #pragma GCC unroll 64
@ -77,14 +78,14 @@ static inline void thiersort2(uint32_t *arr, uint32_t *temparr, int n, sch_rand_
/* Prefix sum (like in Magyarsort) */ /* Prefix sum (like in Magyarsort) */
uint32_t prev = 0; uint32_t prev = 0;
#pragma GCC unroll 4 #pragma GCC unroll 4
for (int i = 0; i < 256; i++) { for (int i = 0; i < 512; i++) {
bucket[i] += prev; bucket[i] += prev;
prev = bucket[i]; prev = bucket[i];
} }
/* Save end-offsets */ /* Save end-offsets */
#pragma GCC unroll 64 #pragma GCC unroll 64
for(int i = 0; i < 256; ++i) { for(int i = 0; i < 512; ++i) {
bucket_end[i] = bucket[i]; bucket_end[i] = bucket[i];
} }
@ -101,7 +102,7 @@ static inline void thiersort2(uint32_t *arr, uint32_t *temparr, int n, sch_rand_
/* temparr -> arr each bucket and sort them in-place */ /* temparr -> arr each bucket and sort them in-place */
#pragma GCC unroll 64 #pragma GCC unroll 64
for(int b = 0; b < 256; ++b) { for(int b = 0; b < 512; ++b) {
int begin = bucket[b]; int begin = bucket[b];
int end = bucket_end[b]; int end = bucket_end[b];
@ -118,18 +119,24 @@ static inline void thiersort2(uint32_t *arr, uint32_t *temparr, int n, sch_rand_
uint32_t pivot = temparr[i]; uint32_t pivot = temparr[i];
#pragma GCC unroll 4 #pragma GCC unroll 4
for(int j = begin + 1; j < end; ++j) { for(int j = begin + 1; j < end; ++j) {
if(UNLIKELY(temparr[j] == pivot)) { if(LIKELY(temparr[j] != pivot)) {
/* Branchless partitioning */
/* copy to left */
/* Rem.: Because we overwrite by copy we can simplify this line */
/* arr[smalli] = (temparr[j] < pivot) ? temparr[j] : arr[smalli]; */
arr[smalli] = temparr[j];
smalli += (temparr[j] < pivot);
/* copy to right */
/* Rem.: Because we overwrite by copy we can simplify this line */
/* arr[biggi] = (temparr[j] > pivot) ? temparr[j] : arr[biggi]; */
arr[biggi] = temparr[j];
biggi -= (temparr[j] > pivot);
} else {
/* swap to front partition */ /* swap to front partition */
++i; ++i;
uint32_t tmp = temparr[i]; uint32_t tmp = temparr[i];
temparr[i] = temparr[j]; temparr[i] = temparr[j];
temparr[j] = tmp; temparr[j] = tmp;
} else if(temparr[j] < pivot) {
/* copy to left */
arr[smalli++] = temparr[j];
} else {
/* copy to right */
arr[biggi--] = temparr[j];
} }
} }
/* Copy the mid elements back */ /* Copy the mid elements back */

8
ypsu.cpp
View File

@ -859,8 +859,8 @@ void measure_single(int n) {
int main(void) { int main(void) {
//int n = 100000000; //int n = 100000000;
int n = 10000000; //int n = 10000000;
//int n = 5000000; int n = 5000000;
//int n = 1000000; //int n = 1000000;
//int n = 100000; //int n = 100000;
//int n = 20001; //int n = 20001;
@ -875,8 +875,8 @@ int main(void) {
printf("Sorting %d elements:\n\n", n); printf("Sorting %d elements:\n\n", n);
// Uncomment this for profiling and alg! // Uncomment this for profiling and alg!
measure_single(n); //measure_single(n);
return 0; //return 0;
for (auto inputtype : inputtypes) { for (auto inputtype : inputtypes) {
printf("%10s", inputtype.c_str()); printf("%10s", inputtype.c_str());