Sorting is one of most classic algorithmic problem in computer science and its fundamental importance has led to the design and implementation of sorting algorithms on recently evolved many-core Graphic Processing Units (GPUs). CUDPP Radix sort has been the most ecient non-comparison sort for a period of time, and recently published GPU Sample sort is considerably the best comparison-based sort. Though the sorting implementations are quite ecient, they either need extra space for data rearrangement or atomic operation for acceleration. Applications runningon GPU usually deal with huge amount of data thus memory utilization is an important consideration. Also, sorting algorithms on GPUs that do not support atomic operations can result in performance degradation or even fail to work. In this paper, we propose an implementation of a shellsort algorithm for NVIDIA's GPUs. It is an in-place sort and requires no atomic operation support. Our experimental result shows that, on average, its performance is nearly twice faster than GPU quicksort and nearly three times faster than Thurst mergesort. Its performance is almost
the same as GPU sample for sorting up to 32M data elements.
Our implementation is robust to various input distributions and should also be well suited for other many-core architectures.

在計算機科學的研究領域，排序法是一直不斷被拿出來討論的問題之一；由於排序法的基礎性和重要性，使得它現在也廣泛被移植到新興的多核心圖形處理器(GPUs)上。在CUDPP函式庫裡的 GPU radix sort 是一種非比較式的(non-comparison-based)排序法，它是目前在GPU上最快的排序法；而 GPU sample sort 是GPU上最快的比較式(comparison-based)排序。這兩個排序法，分別是兩種不同排序分類裡的領先技術(state of the art)；不過它們都需要使用到額外的空間來重組資料，或是使用不可分割運算(atomic operation)來加速。GPU通常被用來處理非常大量的資料，因此，記憶空間的運用顯得特別重要；另外，排序法在沒有不可分割運算(atomic operation)支援的GPU上執行，可能導致效能下降，或甚至無法正常執行。在這個論文裡，我們提出一個在 NVIDIA GPU 上實現shell排序的方法。這個方法不用額外的記憶空間，也不需要不可分割運算的支援。我們的實驗結果也顯示，GPU shellsort 平均上有 GPU quicksort 的兩倍快，與將近快過三倍 Thrust　mergesort 。在小於三千兩百萬筆資料時，效能大概和目前比較式排序的中最快的 GPU sample sort 相當。我們所提出在GPU上的 shell 排序法 ，在各種資料分佈上的表現也都非常穩健，沒有一種標準測試用的資料分佈會使這個方法的效能變的非常差。基本上這個方法也適用其它的多核心平台。

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