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Avoid malloc overhead for small arrays in ptsort #403

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Merged
christian-rauch merged 1 commit into from
Oct 7, 2025
Merged

Avoid malloc overhead for small arrays in ptsort #403

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16 changes: 13 additions & 3 deletions apriltag_quad_thresh.c
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Original file line number Diff line number Diff line change
Expand Up @@ -714,8 +714,16 @@ static inline void ptsort(struct pt *pts, int sz)
#undef MAYBE_SWAP

// a merge sort with temp storage.

struct pt *tmp = malloc(sizeof(struct pt) * sz);
// Use stack allocation for small arrays to avoid malloc overhead
#define STACK_BUFFER_SIZE 256
struct pt stack_buffer[STACK_BUFFER_SIZE];
struct pt *tmp;
const bool use_heap = sz > STACK_BUFFER_SIZE;
if (use_heap) {
tmp = malloc(sizeof(struct pt) * sz);
} else {
tmp = stack_buffer;
}

memcpy(tmp, pts, sizeof(struct pt) * sz);

Expand Down Expand Up @@ -749,7 +757,9 @@ static inline void ptsort(struct pt *pts, int sz)
if (bpos < bsz)
memcpy(&pts[outpos], &bs[bpos], (bsz-bpos)*sizeof(struct pt));

free(tmp);
if (use_heap) {
free(tmp);
}

#undef MERGE
}
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