共查询到20条相似文献，搜索用时 31 毫秒
1.
Using digital elevation models (DEMs), viewshed analysis algorithms determine the visibility of each point on the terrain at a given location in space. As a data-parallel algorithm, real-time viewshed analysis from grid DEM poses a practical challenge to personal computer (PC) users, particularly when dealing with higher resolution and accuracy of large terrain data. Therefore, this paper presents a universal domain decomposition algorithm based on an equal-area strategy for the parallel viewshed analysis on a PC cluster system. The approach uses a scan-line filling method for data partitioning of the irregular bounding polygon of the terrain. The terrain data are divided into sectors of the same area that are connected by the viewpoint and the region vertices, ignoring the null value (or NODATA) points. Furthermore, each sector is assigned to one processor and is organized in the form of triples composed of location and elevation at one point. An index of triples is built to store all of the locations of terminal vertices row-by-row and thus the random access of any point is achieved by using the offsets in each row. Two commonly applied viewshed algorithms, namely, “reference plane” and “Xdraw” algorithms are employed to verify the performance. In addition, two experiments focus on evaluating the efficiency performance and comparing traditional implementation, respectively. Experimental results demonstrate a significant performance improvement compared with the sequential computing method. The memory usage gradually decreases as the number of processors increases. Based on the equal-area decomposition, partitions in terms of sectors can guarantee a suitable load balance. Additional benefits of the proposed solution also include high storage efficiency and program portability. 相似文献
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条件模拟是一种计算非常耗时的高精度三维插值算法。针对串行条件模拟算法计算时间过长的问题,提出基于GPU的并行条件模拟算法,并进行储量估算。对条件模拟算法进行并行分析,利用GPU的高度并行性,构建CUDA通用计算开发环境,实现串行条件模拟算法到并行条件模拟算法的转换,使条件模拟算法的时间复杂度从O(n)降至O(logn)。并对西藏甲玛铜矿进行了储量估算。实验结果表明,在安装普通NVIDIA显卡的计算机以及估算精度不下降的情况下,GPU并行条件模拟的计算效率比CPU串行条件模拟的计算效率提高了60倍以上。 相似文献
3.
The iteratively re-weighted least squares (IRLS) is a commonly used algorithm which has received significant attention in geophysics and other fields of scientific computing for regularization of discrete ill-posed problems. The IRLS replaces a difficult optimization problem by a sequence of weighted linear systems. The optimum solution of the original problem is usually determined by computing the solution for various regularization parameters λ, each needing several re-weighted iterations (usually 10–15). In this paper, in order to decrease the required computation time (iterations) while maintaining good properties of the algorithm such as edge-preserving, the IRLS is augmented with a refinement strategy and the value of λ is progressively updated in a geometrical form during the iterations. The new algorithm, called iteratively re-weighted and refined least squares (IRRLS), can be interpreted as a Landweber iteration with a non-stationary shaping matrix which is updated based on the solution obtained from previous iteration. Two main properties of IRRLS are (1) the regularization parameter is the stopping iteration and (2) it is equipped with a tuning parameter which makes it flexible for recovering models with different smoothness. We show numerically that both the residual and regularization norms are monotone functions of iteration and hence well behaved for automatic determination of stopping parameter. The Stain’s unbiased risk estimate (SURE), generalized cross validation (GCV), L-curve analysis, and discrepancy principle (DCP) techniques are employed for automatic determination of optimum iteration. Experimental results from seismic deconvolution and seismic tomography are included showing that the proposed methodology outperforms the conventional IRLS with significantly lower computational burden. 相似文献
4.
通过对局地集合变换卡尔曼滤波(LETKF)算法的计算时间复杂度的完整分析,发现计算集合空间分析场误差协方差的逆矩阵这一过程计算量最大,耗时最长。且在并行计算环境下,该步骤CPU计算量分配不均是影响计算效率的直接原因。为解决这一问题,采用“贪心算法”设计了一套新的负载均衡策略,并使用该策略开发了一个基于LETKF和并行海洋模块2(POP2)的高性能并行海洋资料同化系统。将2004年1~2月日平均的最优插值海表温度资料(OISST)和同时期的Argo温盐剖面资料同化进入POP2。结果表明,同化有效降低了温度和盐度的均方根误差。同时,在不改变计算结果的前提下,相比原始同化系统,新系统计算性能提升1倍。在更高分辨率(0.1°×0.1°)下,该系统的计算性能仍然可以提升1倍,说明新设计的负载均衡方案稳定可靠。该方案具有很强的可扩展性和移植性,在业务预报中有广泛的应用前景。 相似文献
5.
随着地球物理设备和探测技术的不断发展,快速处理大规模地球物理数据的需求也随之增长。为了解决三维重力数据密度反演的耗时问题,提出一种并行的预处理共轭梯度算法来提高计算效率。本文分别采用两种不同的预处理算子通过组合模型数据反演进行测试比较,并利用迭代残差和计算用时共同评价其加速效果。结果表明：对称逐次超松弛预处理方法比对角预处理方法反演计算速度快,密度结果更贴近实际模型;与传统串行的共轭梯度算法相比,本文并行预处理快速算法可以获得近19倍的加速比。将该算法应用于美国Vinton盐丘的实测重力数据中,反演结果能够很好地圈定出岩体的位置,验证了本文并行预处理共轭梯度法在三维重力数据快速反演中的高效性和可行性。 相似文献
6.
Gang-Hai Huang Yuan-Zhen Xu Xiong-Wei Yi Ming Xia Yu-Yong Jiao Shu Zhang 《国际地质力学数值与分析法杂志》2020,44(9):1301-1314
The efficiency of solving equations plays an important role in implicit-scheme discontinuous deformation analysis (DDA). A systematic investigation of six iterative methods, namely, symmetric successive over relaxation (SSOR), Jacobi (J), conjugate gradient (CG), and three preconditioned CG methods (ie, J-PCG, block J-PCG [BJ-PCG], and SSOR-PCG), for solving equations in three-dimensional sphere DDA (SDDA) is conducted in this paper. Firstly, simultaneous equations of the SDDA and iterative formats of the six solvers are presented. Secondly, serial and OpenMP-based parallel computing numerical tests are done on a 16-core PC, the result of which shows that (a) for serial computing, the efficiency of the solvers is in this order: SSOR-PCG > BJ-PCG > J-PCG > SSOR>J > CG, while for parallel computing, BJ-PCG is the best solver; and (b) CG is not only the most sensitive to the ill-condition of the equations but also the most time consuming under both serial and parallel computing. Thirdly, to estimate the effects of equation solvers acting on SDDA computations, an application example with 10 000 spheres and 200 000 calculation steps is simulated on this 16-core PC using serial and parallel computing. The result shows that SSOR-PCG is about six times faster than CG for serial computing, while BJ-PCG is about four times faster than CG for parallel computing. On the other hand, the whole computation time using BJ-PCG for parallel computing is 3.37 hours (ie, 0.061 s per step), which is about 36 times faster than CG for serial computing. Finally, some suggestions are given based on this investigation result. 相似文献
7.
An integrated analysis about computational time complexity of the Local Ensemble Transform Kalman Filter (LETKF) was performed. It is found that the calculation step of inverse matrix of the error covariance in ensemble space is the most computationally intensive and time consuming. In a parallel computing environment, the uneven distribution of CPU calculations in this step directly leads to low computational efficiency. To solve this problem, a new load balancing strategy was designed based on the "greedy algorithm". A high-performance parallel ocean data assimilation system based on the LETKF was developed and tested using this strategy. This system was based on the Parallel Ocean Program 2 (POP2) of the Community Earth System Model (CESM). The optimal interpolated sea surface temperature data (OISST) and Argo temperature profile data from January to February, 2004 were assimilated into the POP2. The results show that data assimilation effectively reduces the root mean square error of temperature and salinity. Using the new strategy, the exact same results are obtained but the computation time is reduced by half. At higher resolution (0.1°×0.1°),the computing performance is still doubled, indicating that this load balancing scheme is stable and reliable. In addition, the new method has high scalability and portability with great potential to be applied in operational forecasting. 相似文献
8.
非连续变形分析（DDA）方法严格满足平衡要求和能量守恒,具有完全的运动学及数值可靠性,但对大规模岩土工程问题的数值模拟耗时太长,尤其是线性方程组求解,并行计算可以很好地解决该问题。首先基于DDA方法的基本理论,阐述了适用于DDA方法中的基于块的行压缩法和基于“试验-误差”迭代格式的非零位置记录;其次,引入块雅可比迭代法并行求解DDA方法的线性方程组,并改进了相应的非零存储方法;最后,基于OpenMP实现了DDA线性方程组求解并行计算,并将其应用于地下洞室群的破坏过程分析,以加速比为并行效率的指标评价,结果表明,该并行计算策略可以极大提高DDA的计算效率,而且适合各种规模的问题。 相似文献
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10.
随着岩土工程规模的不断扩大、复杂性的增加以及计算参数的多样化和计算精度的提高, 人们对于计算机计算能力的要求越来越高, 然而单处理器无法满足这类大规模计算.从数据输入、区域分解、线性方程组的迭代求解、后处理等方面详细阐述高性能计算平台上并行有限元求解大规模岩土工程的关键问题.提出了利用MPI2的新特性进行海量数据的分段并行读入, 采用ParMetis软件并行地进行区域分解, 实现了前处理过程的完全并行化; 采用基于Jacobi预处理技术的预处理共轭梯度法(PCG)进行线性方程组的并行迭代求解; 采用Paraview软件实现了后处理的并行可视化.在深腾7000系统上对某隧道工程的三维开挖过程进行了数值模拟, 对其并行性能进行了分析和评价, 验证了采用的区域分解算法和系统方程组的求解方法的可行性, 并且具有较高的加速比和并行效率. 相似文献
11.
基于CUDA的地震相干体并行算法 总被引：1，自引：0，他引：1
相干体技术在地震勘探资料解释方面得到了广泛的应用,由于相干体技术处理的对象是三维地震数据体,所以算法运算时间较长。为了缩短解释周期,本文充分发挥GPU并行计算优势,对C3相干体算法进行并行化分析。从硬盘读取数据到GPU上计算相干值并写入硬盘的整个过程进行分析,剔除了冗余数据的读取,完成了C3相干体算法的并行化设计与实现。最后分别对串行算法与并行算法进行性能测试,结果表明本文设计的并行算法在保证精度的前提下达到了16倍左右的加速比,对加快地震资料解释具有重要意义。 相似文献
12.
随着计算机技术的发展,以消息传递接口(MPI)标准为代表的高性价比集群计算技术使并行计算在大量传统的专业领域也得到了广泛应用.数字流域模型因需要对大范围流域进行分布式的水文、泥沙过程模拟而提出了较大规模的计算需求.同时,基于分水岭的单元划分方式和专门的河网编码方法使数字流域模型的并行化计算具有先天优势.提出了一种典型的并行调度流程,用于完成产汇流计算的动态任务分配.在自主搭建的MPI计算集群上进行的应用实验表明,集群计算提高了数字流域模型的计算效率,能够作为模型的计算平台.最后指出了此应用计算平台的发展方向. 相似文献
13.
射频大地电磁法(Radio-magnetotelluric, RMT)是浅地表电磁勘探的重要手段之一。由于勘探频段为10～300 kHz,其电磁场传播受地下介质介电常数的影响较大。传统准静态条件下的电磁响应严重制约RMT正演模拟精度,并进一步影响反演成像分辨率。针对这一问题,提出了一种基于Julia并行加速的全电流RMT电磁响应数值模拟方法,利用Julia的分布式计算将各频点的计算发送到不同进程进行求解,从而达到加速计算的目的,同时在计算中考虑位移电流的影响,提升正演的模拟精度。通过计算几种典型高阻/高介电模型的RMT响应,分析并总结了位移电流对射频段电磁场视电阻率及相位响应的影响规律。数值模拟结果表明：当浅部存在高阻覆盖层时,基于准静态假设条件计算的RMT视电阻率和相位响应偏高,且频率越高、覆盖层电阻率越大,响应偏差越大;对于煤炭采空区模型,RMT法能有效反映异常体位置,但忽略位移电流会在采空区及其附近引起较大计算误差;起伏地形的算例表明地形会覆盖地下异常体的RMT数值响应,尤其是地形拐角处;2种不同规模的并行算例对比证明了并行算法的高效性,且随着求解问题规模增大,并行算法效率也随之... 相似文献
14.
基于GPU的地形可视化加速算法研究 总被引：1，自引：0，他引：1
地形可视化是利用数字高程模型DEM,采用计算机图形学和图像处理技术进行三维地形模拟显示。该技术在深部矿产预测、矿产资源评价、虚拟现实、娱乐游戏、飞行模拟等诸多领域有着广泛的应用。随着数据量的增大,三维地形可视化的实时、流畅视觉效果受到当前的计算机硬件技术水平限制。针对这一问题,本文运用ROAM算法进行地形建模,利用GPU高速并行运算性能加速地形可视化建模速度,加速模型显示效果。实验对比表明:当计算量比较小时,加速效果不显著;随着计算量的增大,计算效果越来越明显;当计算量达到一定值时,加速效果达到一个稳定的加速趋势。研究结果为地形可视化及矿产资源评价等类似工作提供了原创性可视化技术支撑。 相似文献
15.
The release of a digital elevation model (DEM) for Australia on a 9″ (～250 m) grid has enabled the computation of gravimetric terrain corrections thus allowing the computation of complete Bouguer anomalies across the continent. The terrain correction was calculated through a two‐dimensional fast Fourier transform algorithm applied to a linear, planar approximation of the terrain‐correction formula, and with a constant topographic density of 2670 kg.m‐3. The technique was applied to two datasets in order to test for instabilities in the terrain‐correction algorithm: the original 9″ DEM, and a 27″ DEM averaged from the 9″ data. The 27″ terrain corrections were compared with values supplied by the Australian Geological Survey Organisation in Tasmania: 86% of these data were found to agree within 3.91 μm.s‐2; 98% agreed to within 5.32 μm.s‐2 (1σ). 相似文献
16.
由于岩土工程地质条件的复杂性及其规模的不断增大,对大规模数值计算速度的要求越来越高。显卡核心单元（GPU）由于其硬件构造特殊,有着并行计算上的独特优势、高速浮点运算性能和超高的内存带宽,可以很好地解决大规模的科学计算速度问题。文中介绍了GPU与CPU的硬件构架差异,总结了多核CPU、工作站等方式发展的局限性及GPU在并行运算方面的优势,详细阐述了GPU各类计算模式的发展特点及其成果,展示了其在坝区渗透特性中随机微分方程加速求解过程中的优越性,探讨了采用GPU进行大规模岩土工程数值计算的应用前景。 相似文献
17.
In this paper, we study on a history matching approach that consists of finding stable approximations to the problem of minimizing the weighted least-squares functional that penalizes the misfit between the reservoir model predictions G(u) and noisy observations y η . In other words, we are interested in computing an approximation to the minimizer of $\frac {1}{2}\vert \vert \Gamma ^{-1/2}(y^{\eta }-G(u))\vert \vert _{Y}^{2} $ where Γ is the measurements error covariance, Y is the observation space, and X is a set of admissible parameters. This is an ill-posed nonlinear inverse problem that we address by means of the regularizing Levenberg–Marquardt scheme developed by Hanke (Inverse Probl. 13:79–95, 1997; J. Integr. Equ. Appl. 22(2):259–283, 2010). Under certain conditions on G, the theory of Hanke (Inverse Probl. 13:79–95, 1997; J. Integr. Equ. Appl. 22(2):259–283, 2010) ensures the convergence of the scheme to stable approximations to the inverse problem. We propose an implementation of the regularizing Levenberg–Marquardt scheme that enforces prior knowledge on the geologic properties. In particular, the prior mean $\overline {u}$ is incorporated in the initial guess of the algorithm, and the prior error covariance C is enforced through the definition of the parameter space X. Our main goal is to numerically show that the proposed implementation of the regularizing Levenberg–Marquardt scheme of Hanke is a robust method capable of providing accurate estimates of the geologic properties for small noise measurements. In addition, we provide numerical evidence of the convergence and regularizing results predicted by the theory of Hanke (Inverse Probl. 13:79–95, 1997; J. Integr. Equ. Appl. 22(2):259–283, 2010) for a prototypical oil–water reservoir model. The performance for recovering the true permeability with the regularizing Levenberg–Marquardt scheme is compared to the typical approach of computing the maximum a posteriori (MAP) estimator. In particular, we compare the proposed application of the regularizing Levenberg–Marquardt (LM) scheme against the standard LM approach of Li et al. (SPE J. 8(4):328–340, 2003) and Reynolds et al. (2008) for computing the MAP. Our numerical experiments suggest that the history matching approach based on iterative regularization is robust and could potentially be used to improve further on various methodologies already proposed as effective tools for history matching in petroleum reservoirs. 相似文献
18.
基于遗传算法的新安江模型日模拟参数优选研究 总被引：7，自引：0，他引：7
在概念性水文模型的参数率定中,目前还没有一个传统优化方法能够提供保证足够高效和稳定性的算法。为了克服传统优化方法中局部收敛性的缺点,近年来利用遗传算法通过计算机准确稳定地进行概念性水文模型的参数优选的尝试得到越来越多的重视和发展。目前优选水文模型待定参数,大多是从次洪模型的方面去讨论,有关日模拟模型的遗传算法参数优选讨论的较少。本文系统分析了基于遗传算法的新安江模型日模拟参数的自动优选,同时针对遗传算法在模型参数众多的情况下时间效率低下问题,通过利用新安江模型参数分层原理与模型参数敏感性分析对优选结果影响,提出一套简化的日模型参数遗传算法优选方案。经过流域模拟检验,该优选方案可行,运行效率高,可以作为类似模型遗传算法参数率定快速、有效的方案。 相似文献
19.
基于粗细网格的有限元并行分析方法 总被引：2，自引：0，他引：2
并行计算己成为求解大规模岩土工程问题的一种强大趋势。探讨了粗细网格与预处理共轭梯度法结合的并行有限元算法。从多重网格刚度矩阵推得有效的预处理子。该算法在工作站机群上实现。用地基处理时土体强夯的数值模拟分析进行了数值测试,对其并行性能进行了详细分析。计算结果表明：该算法具有良好的并行加速比和效率,是一种有效的并行算法。 相似文献
20.
地球物理勘探技术日新月异,地球物理勘探数据的处理和解释对高性能计算机的要求越来越高.相比于地震勘探,重力、磁法、电法勘探中的并行计算研究还都处于起步阶段.基于GPU的并行计算能够提供强大的计算能力和存储器带宽,同时具有良好的可编程性、较低的成本和较短的开发周期.这里实现了瞬变电磁法一维正演计算中汉克尔变换基于GPU的并行计算,比较了汉克尔变换串行算法和并行算法的计算耗时,基于GPU技术的并行计算相比串行计算,获得了很高的加速比. 相似文献