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schwab: selection sort trying...

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This commit is contained in:
Richard Thier 2025-05-09 06:01:44 +02:00
parent 266f489002
commit c1d152c6f9
1 changed files with 32 additions and 5 deletions
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37
schwab_sort.h
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@ -17,7 +17,12 @@
/** Below this many elements we do insertion sort */ /** Below this many elements we do insertion sort */
#ifndef SCHWAB_INSERTION_THRESHOLD #ifndef SCHWAB_INSERTION_THRESHOLD
#define SCHWAB_INSERTION_THRESHOLD 128 #define SCHWAB_INSERTION_THRESHOLD 128
#endif /* SCHWAB_DELTA_THRESHOLD */ #endif /* SCHWAB_INSERTION_THRESHOLD */
/** Below this many elements we do insertion sort */
#ifndef SCHWAB_SELECTION_THRESHOLD
#define SCHWAB_SELECTION_THRESHOLD 16
#endif /* SCHWAB_SELECTION_THRESHOLD */
typedef uint32_t sch_rand_state; typedef uint32_t sch_rand_state;
@ -65,7 +70,7 @@ inline void sch_insertion_sort(uint32_t *arr, int low, int high) {
/** Simple insertion sort for small cases v2 - not necessarily better */ /** Simple insertion sort for small cases v2 - not necessarily better */
inline void sch_insertion_sort2(uint32_t* arr, int low, int high) { inline void sch_insertion_sort2(uint32_t* arr, int low, int high) {
for(size_t i = low + 1; i <= high; ++i) { for(int i = low + 1; i <= high; ++i) {
uint32_t key = arr[i]; uint32_t key = arr[i];
/* Separate load and compare to expose ILP */ /* Separate load and compare to expose ILP */
@ -81,6 +86,23 @@ inline void sch_insertion_sort2(uint32_t* arr, int low, int high) {
} }
} }
/** Simple SELECTION sort for small cases - not necessarily better */
inline void sch_selection_sort(uint32_t* arr, int low, int high) {
#pragma GCC unroll 2
for(int i = low; i < high; ++i) {
/* Min-search remaining array */
int mini = i;
#pragma GCC unroll 4
for(int j = i + 1; j < high + 1; ++j) {
if(arr[j] < arr[mini]) mini = j;
}
if(mini != i) {
schwab_swap(&arr[i], &arr[mini]);
}
}
}
/** /**
* 3-way partitioning, in middle all the pivot elements. * 3-way partitioning, in middle all the pivot elements.
* *
@ -316,9 +338,14 @@ static inline void schwab_sort(
high = plo - 1; high = plo - 1;
} }
} else { } else {
/* Just do an insertion sort instead */ if(high - low > SCHWAB_SELECTION_THRESHOLD) {
sch_insertion_sort(array, low, high); /* Just do an insertion sort instead */
return; sch_insertion_sort(array, low, high);
return;
} else {
sch_selection_sort(array, low, high);
return;
}
} }
} }
} }