High parallelization efficiency in barotropic-mode computation of ocean models based on multi-grid boundary ghost area   总被引：1，自引：0，他引：1  

Hiroshi Ishizaki  Ichiro Ishikawa 《Ocean Modelling》2006,13(3-4):238-254

In general, barotropic-mode computation requires the largest communication time in ocean models because of its iterative nature, when parallel computation is performed based on regional partitioning. In this study, reduction in the overhead time included in the communication in the parallel computation of the barotropic mode is considered to achieve a high parallelization efficiency of ocean models. We verify that the reduction in the communication frequency based on the multi-grid boundary ghost area reduces the total communication time. We find that this is because the sum of several kinds of overhead time for communication occupies a fairly large part of the total communication time. We discuss the trade-off between the decrease in communication time and the increase in computation time due to increased boundary area in such cases, leading to a determination of a suitable width of the multi-grid boundary that minimizes the total required time. We also discuss the efficiencies of the one- and two-dimensional partitioning of the model domain, when a multi-grid boundary is used. In general, two-dimensional partitioning is more efficient than one-dimensional for large partitioning numbers.  相似文献   

Efficient GOCE satellite gravity field recovery based on least-squares using QR decomposition   总被引：3，自引：0，他引：3  

Oliver Baur  Gerrit Austen  Jürgen Kusche 《Journal of Geodesy》2008,82(4-5):207-221

We develop and apply an efficient strategy for Earth gravity field recovery from satellite gravity gradiometry data. Our approach is based upon the Paige-Saunders iterative least-squares method using QR decomposition (LSQR). We modify the original algorithm for space-geodetic applications: firstly, we investigate how convergence can be accelerated by means of both subspace and block-diagonal preconditioning. The efficiency of the latter dominates if the design matrix exhibits block-dominant structure. Secondly, we address Tikhonov-Phillips regularization in general. Thirdly, we demonstrate an effective implementation of the algorithm in a high-performance computing environment. In this context, an important issue is to avoid the twofold computation of the design matrix in each iteration. The computational platform is a 64-processor shared-memory supercomputer. The runtime results prove the successful parallelization of the LSQR solver. The numerical examples are chosen in view of the forthcoming satellite mission GOCE (Gravity field and steady-state Ocean Circulation Explorer). The closed-loop scenario covers 1 month of simulated data with 5 s sampling. We focus exclusively on the analysis of radial components of satellite accelerations and gravity gradients. Our extensions to the basic algorithm enable the method to be competitive with well-established inversion strategies in satellite geodesy, such as conjugate gradient methods or the brute-force approach. In its current development stage, the LSQR method appears ready to deal with real-data applications.  相似文献   

Electrical aerosol spectrometer of Tartu University     

H. Tammet  A. Mirme  E. Tamm   《Atmospheric Research》2002,62(3-4)

The electrical aerosol spectrometer (EAS) of the parallel measuring principle at Tartu University is an efficient instrument for rapid measurement of the unstable size spectrum of aerosol particles. The measuring range from 10 nm to 10 μm is achieved by simultaneously using a pair of differential mobility analyzers with two different particle chargers. The particle spectrum is calculated and measurement errors are estimated in real time by using a least-squares method. Experimental calibration ensures reliability of measurement. The instrument is well suited for continuous monitoring of atmospheric aerosol.  相似文献   

一种在异构系统中实现负载平衡的方法   总被引：2，自引：3，他引：2       下载免费PDF全文

金之雁  王鼎兴 《应用气象学报》2003,14(4):410-418

提出了在异构系统实现负载平衡的区域分解算法和实现负载平衡的计算方法，利用它的负反馈性质解决了异构系统处理机计算速度测量误差造成的负载测量不准问题，并对处理机速度变化，速度测量误差、处理机数量、网格点计算量的分布等因素的影响进行了计算，结果表明本方法具有很强的平衡负载能力和较强的适应性；根据计算结果提出了解决模式网格点计算量不易测量问题的解决方案，并用扩散方程和模拟物理过程进行试验，试验表明这种方法是可行的，平衡负载的效果十分显著。  相似文献   

一种符合视觉规律的,基于地图数据的虚拟地景仿真   总被引：5，自引：1，他引：5  

陈刚 《测绘学报》1997,26(3):241-246

本文分析和解决了两个关键性问题，使计算机所生成的虚拟地景符合人的“越近看得越清”视觉规律，并通过实例对该方法的实现过程给予了详细的描述。  相似文献   

Fast space-domain evaluation of geodetic surface integrals     

R. Lehmann 《Journal of Geodesy》1997,71(9):533-540

Geodetic surface integrals play an important role in the numerical solution of geodetic boundary-value problems. In many cases they can be evaluated using fast methods in the frequency domain (FFT). However, this is not possible in general, because the domain of integration may be non-trivial (as is the surface of the Earth), the kernel function may not be of convolution type, or the data distribution may be heterogeneous. Therefore, fast evaluation strategies are also required in the space domain. They are more difficult to design because only one property is left where a more or less fast evaluation strategy can be built upon: the potential type of the kernel function. Consequently, the idea is not to replace well-established frequency domain techniques, but to supplement them. Our approach to this problem goes in two directions: (1) we use advanced cubature methods where the integration nodes automatically densify in the vicinity of the evaluation points; (2) we use powerful computer hardware, namely MIMD computers with distributed memory. This enables us to evaluate geodetic surface integrals of any practical complexity in reasonable time and accuracy. This is shown in a numerical example. Received: 7 May 1996 / Accepted:17 March 1997  相似文献   

τ-P域地震资料三维叠前深度偏移及其实用算法   总被引：3，自引：2，他引：3       下载免费PDF全文

贺振华  陈志文 《地球物理学报》1997,40(2):257-264

本文提出了在τ-P域实现三维叠前深度偏移的计算方法，该方法把地震道集由时-空域变换到τ-P域，然后对共P数据体进行相移或相移加插值偏移，将偏移后的各共P数据体叠加得到叠前深度偏移结果．该算法能够实现陡倾地层的正确归位，降低偏移处理维数，减少计算机内存需求，易于并行处理，但是计算量和所花费的计算机时间仍然很大．为此我们又提出了针对目的层的分时（层）偏移方法，由于只考虑目的层，可节省大量的计算时间．文中以二维实际地震资料及三维数值模型资料的处理说明了上述方法的可行性与有效性．  相似文献   

台风路径数值预报模式的并行化及路径预报误差分析   总被引：3，自引：6，他引：3       下载免费PDF全文

麻素红  瞿安祥张眙 《应用气象学报》2004,15(3):322-328

国家气象中心台风路径数值预报模式经过串行优化及程序并行, 成功地实现了在国产超级计算机神威上的并行运算, 并可满足业务时效要求。基于并行程序及神威机计算平台的台风路径数值预报业务系统于2002年6月30日投入实时运行, 其初估场与侧边界条件从T106L19模式产品升级为T213L31模式产品 (称为基于T213台风预报系统, 原串行系统称为基于T106台风预报系统)。通过对2002年夏秋季台风路径的检验, 总体来看, 基于T213台风预报系统48 h内的平均路径预报误差小于基于T106台风预报系统的路径预报误差。对西行及西北行登陆的台风, 基于T106台风预报系统的48 h预报好于基于T213台风预报系统的预报。对于转向台风而言, 转向后的预报, 基于T213台风预报系统的预报要好于基于T106台风预报系统的预报, 有效地减小了基于T106台风预报系统对转向台风路径预报的系统性误差:即台风转向后预报路径较实况路径偏西。  相似文献   

三江并流世界自然遗产地旅游地质景观成景地质作用初步分析     

王嘉学  明庆忠  杨世瑜  彭秀芬 《云南地理环境研究》2005,17(3):53-56,80

三江并流世界自然遗产地丰富独特的旅游地质景观是多种地质作用与不同成景岩组交互叠加作用的结果。其发育的地层基础主要为碳酸盐成景岩组、变质岩成景岩组、碎屑岩成景岩组以及岩浆岩成景岩组等,典型内力成景地质作用为板块缝合作用、断裂成景作用、变质成景作用,外力作用则主要有河流、冰川、丹霞、地热、喀斯特作用等。  相似文献   

PMODTRAN: a parallel implementation based on MODTRAN for massive remote sensing data processing     

Fang Huang  Ji Zhou  Xicheng Tan  Shunlin Liang  Jie Cheng 《International Journal of Digital Earth》2016,9(9):819-834

MODerate resolution atmospheric TRANsmission (MODTRAN) is a commercial remote sensing (RS) software package that has been widely used to simulate radiative transfer of electromagnetic radiation through the Earth's atmosphere and the radiation observed by a remote sensor. However, when very large RS datasets must be processed in simulation applications at a global scale, it is extremely time-consuming to operate MODTRAN on a modern workstation. Under this circumstance, the use of parallel cluster computing to speed up the process becomes vital to this time-consuming task. This paper presents PMODTRAN, an implementation of a parallel task-scheduling algorithm based on MODTRAN. PMODTRAN was able to reduce the processing time of the test cases used here from over 4.4 months on a workstation to less than a week on a local computer cluster. In addition, PMODTRAN can distribute tasks with different levels of granularity and has some extra features, such as dynamic load balancing and parameter checking.  相似文献