#ShellSort
Bo Liu
A New Gap Sequence for Shellsort: RL-Driven Algorithm Discovery Beyond $N^{4/3}$
https://arxiv.org/abs/2609.29881
September 25, 2026 at 4:33 PM
Bo Liu: A New Gap Sequence for Shellsort: RL-Driven Algorithm Discovery Beyond $N^{4/3}$ https://arxiv.org/abs/2609.29881 https://arxiv.org/pdf/2609.29881 https://arxiv.org/html/2609.29881
September 25, 2026 at 6:39 AM
Ziqi Zhao, Qingjian Ni: Chronological Certificates for Shellsort: Ray Defects and Signed-Positive Transference https://arxiv.org/abs/2608.10696 https://arxiv.org/pdf/2608.10696 https://arxiv.org/html/2608.10696
August 12, 2026 at 6:38 AM
Chronological Certificates for Shellsort: Ray Defects and Signed-Positive Transference
**Authors:** Ziqi Zhao, Qingjian Ni Shellsort's best general lower and classical upper bounds differ by an iterated-logarithmic factor. Lower bounds use signed, order-free cancellation, whereas upper bounds require positive representations respecting pass order. We develop a common certificate framework for these two geometries. A prefix Fourier phase defect lower-bounds worst-case exchanges and hence comparisons. At pass $j$, the chronological ray quotient records multiples of the current gap already eliminated by earlier passes. Its truncated, pair-weighted hole mass bounds exchanges in that pass, and adding the $np$ overhead bounds comparisons. In a sufficiently long active window, $g_j^{(n)}$ ray holes imply signed transfer length at most $4g_j^{(n)}-1$, so approximate prefix characters propagate to the current gap. Signed transfer length two can coexist with arbitrarily large ray genus; scale-local Apéry representatives control both parameters. The framework recovers Pratt's $O(n\log^2 n)$ scale and the sparse two-parent scale, and yields the following structural results. Uniformly bounded full ray genus after a fixed prefix forces $W_n=Ω(n^{1+1/j_0-o(1)})$ when $p_n-j_0=o(\log n)$. An affine family has ordinary global semigroup genus and conductor $Θ(n)$ but relevant ray genus two. Balanced three-generator full grids have terminal truncated ray genus at least $\exp(Ω((\log n)^{2/3}))$. The last result is a certificate barrier.
arxiv.org
August 12, 2026 at 4:18 AM
Zhenghan Zang
Improved lower bounds of the time complexity of shellsort
https://arxiv.org/abs/2607.08997
July 13, 2026 at 12:52 PM
Zhenghan Zang: Improved lower bounds of the time complexity of shellsort https://arxiv.org/abs/2607.08997 https://arxiv.org/pdf/2607.08997 https://arxiv.org/html/2607.08997
July 13, 2026 at 6:40 AM
When I did need a sort in Pascal, at work over thirty years ago, there was no sort. So I used a Shellsort.

It is not the world’s fastest sort, But it was the best sort known until quicksort came around.
October 24, 2025 at 10:07 PM
Computer science used to be my fav subject and now I have to prepare a presentation on Shellsort and don't understand a single thing help
May 21, 2025 at 5:18 PM
Bubble Sort, Insertion Sort, Merge Sort, Quick Sort, Shell Sort

Description: You will write a program which implements the following sorts and compares the performance for operations on arrays of integers of growing sizes 10, 100, 1000, 5000, 10000, 25000, etc.... You will graph the performance of…
Bubble Sort, Insertion Sort, Merge Sort, Quick Sort, Shell Sort
Description: You will write a program which implements the following sorts and compares the performance for operations on arrays of integers of growing sizes 10, 100, 1000, 5000, 10000, 25000, etc.... You will graph the performance of the different sorts as a function of the size of the array. 1)BubbleSort 2)InsertionSort 3)MergeSort 4)Non-Recursive, one extra array MergeSort (We’ll call this improved version, IterativeMergeSort from here on out in this homework) 5)QuickSort 6)ShellSort
programming.engineering
March 1, 2025 at 9:12 AM
Where's the one with even more of them starting in the correct order and we learn the Hungarian for "should have used shellsort?" :)
October 20, 2024 at 10:14 AM
android_therapy.exe
Using several incomplete #pixelSorting techniques.
#HeapSort #ShellSort #QuickSort #MergeSort #Coding #Processing #pixelSort #pixel
September 15, 2024 at 5:15 PM
Finally, I've been looking for a simple, O(n·log(n)), non-recursive, deterministic, and strictly-in-place sorting algorithm that works well in practice since forever.

If you are able to improve the Shellsort implementation above, please, drop me a line telling me how!
August 15, 2024 at 5:14 PM
The Shellsort variant I posted above is faster, uses less code and uses less memory than all the Heapsort variants I've tried so far.

I know people are usually afraid of using Shellsort, but give it a try to this one before dismissing it!
August 15, 2024 at 5:12 PM
This snippet of code contains a rather uncommon version of Shellsort (with a gap growing factor of 9/4) that works much better than the one you usually find elsewhere on the internet (with a gap growing factor of 3).
August 15, 2024 at 5:11 PM
void shellsort(int *A, size_t n) {

size_t i, j, k;
int t;

for (k = 3; k <= n/9; k = k*9/4 + 1);

for (k = k*4/9; k; k = k*4/9) {
for (i = k; i < n; ++i) {
t = A[i];
for (j = i; k <= j && t < A[j-k]); j -= k) { A[j] = A[j-k]; }
A[j] = t;
}
}
}
August 15, 2024 at 5:11 PM