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schwab insertion - but buggy from some previous at n=20 rand

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This commit is contained in:
Richard Thier 2025-05-09 04:49:31 +02:00
parent 4c67501511
commit 147ca60672
1 changed files with 74 additions and 46 deletions
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28
schwab_sort.h
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@ -14,6 +14,11 @@
#define SCHWAB_DELTA_THRESHOLD 32
#endif /* SCHWAB_DELTA_THRESHOLD */
/** Below this many elements we do insertion sort */
#ifndef SCHWAB_INSERTION_THRESHOLD
#define SCHWAB_INSERTION_THRESHOLD 4
#endif /* SCHWAB_DELTA_THRESHOLD */
typedef uint32_t sch_rand_state;
/** Create rand state for schwab_sort using a seed - can give 0 if uninterested */
@ -41,6 +46,22 @@ static inline void schwab_swap(uint32_t *a, uint32_t *b) {
*b = t;
}
/** Simple insertion sort for small cases */
inline void sch_insertion_sort(uint32_t *arr, int low, int high) {
for (int i = low + 1; i <= high; ++i) {
uint32_t key = arr[i];
int j = i;
/* Move elements of arr[0..i-1] that are greater than key */
/* to one position ahead of their current position */
while (j > 0 && arr[j - 1] > key) {
arr[j] = arr[j - 1];
--j;
}
arr[j] = key;
}
}
/**
* 3-way partitioning, in middle all the pivot elements.
*
@ -221,7 +242,9 @@ static inline void schwab_sort(
sch_rand_state *state) {
/* Loop handles longest sub-sort-task which ensused log tree depth */
/* Loop also handles start condition */
while(low < high) {
if(1 /*high - low > SCHWAB_INSERTION_THRESHOLD*/) {
int r0 = schwab_pick_pivot(state, (high + 1) - low) + low;
int r1 = schwab_pick_pivot(state, (high + 1) - low) + low;
uint32_t klo = array[r0];
@ -273,6 +296,11 @@ static inline void schwab_sort(
/* low = low; */
high = plo - 1;
}
} else {
/* Just do an insertion sort instead */
sch_insertion_sort(array, low, high);
return;
}
}
}