As the flash-based solid-state drives(SSDs) gradually replace the mechanical hard disk drives(HDDs) as the mainstream storage, unlike the HDDs, SSDs have rich internal parallelism, which makes it have the excellent characteristics that HDDs do not have. External mergesort, as the classical algorithm of external sorting adopted in many systems and algorithms, has an important impact on the overall performance. Therefore, it is of great significance to optimize and improve the efficiency of external mergesort algorithm. The research work on optimizing raw external mergesort algorithm on SSDs is relatively few. Thus, aiming at the external mergesort problem, based on the characteristics of SSDs, this paper proposes the SortDecision algorithm which can calculate its optimal execution scheme, including merging way, read buffer size, and write buffer size which determine the execution process of external mergesort. Exploiting the above optimal execution scheme, external mergesort can obtain better efficiency. In the SortDecision algorithm, external mergesort problem on SSDs is formalized and transformed into a piecewise convex optimization problem. Then, the optimal external mergesort scheme is obtained by enumerating the solutions of each subconvex problem. The experimental results show that the external mergesort proceeds guided by SortDecision algorithm can achieve a speedup of 1\(\sim \)6.7 compared to the traditional external mergesort algorithm in the case of limited memory provided. The richer the internal parallelism resources inside SSDs, the better the effect of SortDecision’s acceleration.

随着基于闪存的固态驱动器（SSD）逐渐取代机械硬盘驱动器（HDD）成为主流存储，与HDD不同，SSD具有丰富的内部并行性，这使其具有HDD所没有的出色特性。作为许多系统和算法中采用的经典外部排序算法，外部合并排序对整体性能具有重要影响。因此，优化和提高外部合并排序算法的效率具有重要意义。在SSD上优化原始外部mergesort算法的研究工作相对较少。因此，针对外部归并问题，基于SSD的特性，提出了小号ö ř吨d È Ç我小号我ø Ñ算法可以计算其最佳执行方案，包括合并方式，读缓冲器大小，和写缓冲器尺寸确定外部归并的执行过程。利用上述最佳执行方案，外部合并排序可以获得更好的效率。在小号ö ř吨d È Ç我小号我ø Ñ算法，SSD上外部归并问题形式化并转化成一个分段凸优化问题。然后，通过枚举每个子凸问题的解来获得最佳的外部合并排序方案。实验结果表明，外部合并排序的指导是：小号ö ř吨d È Ç我小号我ø Ñ算法可以实现1:1的加速\（\ SIM \） 6.7相比，在提供了有限的存储器的情况下传统的外部归并排序算法。内部固态硬盘的内部并行资源更丰富，的效果越好小号ö ř吨d È Ç我小号我ö Ñ的加速度。