Multi-reservoir design using Pontryagin principle

Several successful applications of optimal control theory (OCT) based on the Pontryagin's minimum principle have been recorded in literature. These applications were focused on optimizing the operating policy of multi-reservoir systems. In this study, the performance of OCT algorithm in designing multi-reservoir system is investigated. Three deterministic optimization models based on the OCT were developed to design the best storage strategies in a multi-reservoir system to supply water. Multi-objective programming methods were implemented in the three models in order to consider the two non-commensurate objectives of minimizing cost and water deficit. The applications of these models to a multi-reservoir system were compared to an existing dynamic programming model. The result of this study showed that in all cases, the developed OCT models presented sub-optimal solution in designing multi-reservoir systems.     

Stochastic differential dynamic programming for multi-reservoir system control

: As with all dynamic programming formulations, differential dynamic programming (DDP) successfully exploits the sequential decision structure of multi-reservoir optimization problems, overcomes difficulties with the nonconvexity of energy production functions for hydropower systems, and provides optimal feedback release policies. DDP is particularly well suited to optimizing large-scale multi-reservoir systems due to its relative insensitivity to state-space dimensionality. This advantage of DDP encourages expansion of the state vector to include additional multi-lag hydrologic information and/or future inflow forecasts in developing optimal reservoir release policies. Unfortunately, attempts at extending DDP to the stochastic case have not been entirely successful. A modified stochastic DDP algorithm is presented which overcomes difficulties in previous formulations. Application of the algorithm to a four-reservoir hydropower system demonstrates its capabilities as an efficient approach to solving stochastic multi-reservoir optimization problems. The algorithm is also applied to a single reservoir problem with inclusion of multi-lag hydrologic information in the state vector. Results provide evidence of significant benefits in direct inclusion of expanded hydrologic state information in optimal feedback release policies.     

Stochastic differential dynamic programming for multi-reservoir system control

: As with all dynamic programming formulations, differential dynamic programming (DDP) successfully exploits the sequential decision structure of multi-reservoir optimization problems, overcomes difficulties with the nonconvexity of energy production functions for hydropower systems, and provides optimal feedback release policies. DDP is particularly well suited to optimizing large-scale multi-reservoir systems due to its relative insensitivity to state-space dimensionality. This advantage of DDP encourages expansion of the state vector to include additional multi-lag hydrologic information and/or future inflow forecasts in developing optimal reservoir release policies. Unfortunately, attempts at extending DDP to the stochastic case have not been entirely successful. A modified stochastic DDP algorithm is presented which overcomes difficulties in previous formulations. Application of the algorithm to a four-reservoir hydropower system demonstrates its capabilities as an efficient approach to solving stochastic multi-reservoir optimization problems. The algorithm is also applied to a single reservoir problem with inclusion of multi-lag hydrologic information in the state vector. Results provide evidence of significant benefits in direct inclusion of expanded hydrologic state information in optimal feedback release policies.     

大地电磁三维数据空间反演并行算法研究

目前大地电磁三维反演实际应用的主要问题是计算效率低.在对大地电磁三维数据空间反演算法进行深入分析的基础上,本文提出了基于频点和矩阵划分的大粒度并行反演方案和具体实现步骤,并在曙光TC5000A高性能计算平台上实现了基于MPI的大地电磁三维数据空间反演并行算法.该算法实现了包括三维正演、灵敏度矩阵、叉积矩阵以及模型改正量的并行执行,不仅计算效率高,而且每个节点机上灵敏度矩阵的存储空间只需原来微机上的2/N(N是参加并行计算的节点机个数),大大地减少了内存开销.通过两个理论模型合成的数据对实现的三维数据空间反演并行算法进行试算,对比分析了多个节点机下程序的执行效率.测试结果表明,所实现的三维数据空间反演并行算法是可行的、高效的,与单机相比,不仅可以提高运行速度,缩短计算时间,而且还可以扩大计算规模,极大地推动了大地电磁三维反演的实用化.     

A parallel finite–infinite element model for two-dimensional soil–structure interaction problems

A parallel soil–structure interaction (SSI) model is presented for applications on distributed computer systems. Substructring method is applied to the SSI system and a coupled finite–infinite element based parallel computer program is developed. In the SSI system, infinite elements are used to represent the soil which extends to infinity. In this case, a large finite element mesh is required to define the near field for reliable predictions. The resulting large-scale problems are solved on distributed computer systems in this study. The domain is represented by separated substructures and an interface. The number of substructures are determined by the available processors in the parallel platform. To avoid the formation of large interface equations, smaller interface equations are distributed to processors while substructure contributions are performed. This saves a lot of memory storage and computational effort. Direct solution techniques are used for the solution of interface and substructure equation systems. The program is investigated through some example problems. The example problems exposed the need for solving large-scale problems in order to reach better results. The results of the example problems demonstrated the benefits of the parallel SSI algorithm.     

Accelerating Groundwater Flow Simulation in MODFLOW Using JASMIN‐Based Parallel Computing

To accelerate the groundwater flow simulation process, this paper reports our work on developing an efficient parallel simulator through rebuilding the well‐known software MODFLOW on JASMIN (J Adaptive Structured Meshes applications Infrastructure). The rebuilding process is achieved by designing patch‐based data structure and parallel algorithms as well as adding slight modifications to the compute flow and subroutines in MODFLOW. Both the memory requirements and computing efforts are distributed among all processors; and to reduce communication cost, data transfers are batched and conveniently handled by adding ghost nodes to each patch. To further improve performance, constant‐head/inactive cells are tagged and neglected during the linear solving process and an efficient load balancing strategy is presented. The accuracy and efficiency are demonstrated through modeling three scenarios: The first application is a field flow problem located at Yanming Lake in China to help design reasonable quantity of groundwater exploitation. Desirable numerical accuracy and significant performance enhancement are obtained. Typically, the tagged program with load balancing strategy running on 40 cores is six times faster than the fastest MICCG‐based MODFLOW program. The second test is simulating flow in a highly heterogeneous aquifer. The AMG‐based JASMIN program running on 40 cores is nine times faster than the GMG‐based MODFLOW program. The third test is a simplified transient flow problem with the order of tens of millions of cells to examine the scalability. Compared to 32 cores, parallel efficiency of 77 and 68% are obtained on 512 and 1024 cores, respectively, which indicates impressive scalability.     

区域分解法地震正演模拟方法研究

区域分解法是近年开辟的计算偏微分方程数值解的一种新方法，该方法把研究区域分解为形态规则的小区域，在各子区域内采用最有效的方法求解，能充分发挥各种正演模拟方法的优点，大大地提高求解正演问题的有效性．本文首次把区域分解法引入地震正演模拟，构造出了适应性强、计算速度快、所需计算机资源量小，具有高度并行性的区域分解地震正演模拟方法，编制了区域分解地震正演模拟软件，对大量地质模型进行了计算，获得了良好的结果．     

三维地震动场数值模拟并行计算系统

并行计算系统是进行三维复杂场地地震动场数值模拟的基础。本文作者利用10台微机构建了一套并行计算集群(常称为Beowulf系统),节点微机上运行Windows2000操作系统,采用MPI标准的MPICH1．2．4版本作为并行计算的支撑环境,并以100M bps高速交换式以太网作为互连网络。利用编制的并行计算程序对该并行计算系统性能进行了测试。结果表明：该系统能够达到非常高的并行加速比和并行效率。该系统将用于三维地震动场数值模拟研究。     

大地电磁三维交错网格有限差分数值模拟的并行计算研究

为了更有效的提高大地电磁三维正演的计算速度,引入了并行处理技术.大地电磁三维交错网格有限差分数值模拟是按照不同频率来计算的,各频率之间求取电磁场值的过程是相互独立的.根据这一特点,可以将多个频率的计算任务平均划分为一个或者几个频率的计算子任务,分配到各个计算节点去并行执行,计算完成后将结果汇总.本文通过采用主从并行模式、分频并行计算的方案,在曙光TC5000A高性能并行平台上实现了基于MPI的大地电磁三维正演的并行计算.通过两个理论模型对实现的大地电磁三维正演并行算法进行试算,对比分析了多个节点机下程序的执行效率.测试结果表明,所实现的三维正演并行算法是正确的、高效的,为进一步的大地电磁三维反演并行算法研究奠定了重要基础.     

基于云环境的云南地震灾害快速评估与信息服务系统在巧家MS5.0地震中的应用

基于云南地震灾害快速评估系统现状与使用中发现的问题,对其在空间算法、动态集群分布式并行计算、信息服务模式等多方面进行优化,设计了云环境下的云南地震灾害快速评估与信息服务系统,并结合系统在巧家MS5.0地震中的使用情况进行综合分析.结果表明:新的地震灾害应急指挥技术系统产出的应急产品,在时效性与准确性方面均得到较大提高,...     

Dynamic programming approach for segmentation of multivariate time series

In this paper, dynamic programming (DP) algorithm is applied to automatically segment multivariate time series. The definition and recursive formulation of segment errors of univariate time series are extended to multivariate time series, so that DP algorithm is computationally viable for multivariate time series. The order of autoregression and segmentation are simultaneously determined by Schwarz’s Bayesian information criterion. The segmentation procedure is evaluated with artificially synthesized and hydrometeorological multivariate time series. Synthetic multivariate time series are generated by threshold autoregressive model, and in real-world multivariate time series experiment we propose that besides the regression by constant, autoregression should be taken into account. The experimental studies show that the proposed algorithm performs well.     

基于网格的地震模拟工作流调度

网格为地震模拟等大规模工作流应用提供了强大的计算能力,如何保障此类应用的软实时性要求是工作流调度问题的一个挑战.利用排队模型来描述网格资源的动态负载压力,提出了评估工作流健壮性量化指标及其计算方法.基于DAG图转换得出的任务执行优先级,根据最大健壮性优先的思想,确定了执行工作流子任务的候选资源;将工作流全局截止时间划分问题描述为一个约束下的非线性规划问题并通过已有方法求解该问题,提出了工作流全局截止时间动态划分方法;最后,提出了一种健壮性增强的地震模拟工作流调度算法RESAESW.仿真实验采用实际地震模拟工作流应用和实际系统数据来验证提出算法的性能表现,实验结果表明本文算法在网格环境的自适应性和地震模拟工作流应用的截止时间要求方面优于其他两个实际网格系统中的调度算法.     

并行计算技术及其在勘探地球物理学中的现状与展望

本文详细阐述了并行计算技术及其在地球物理勘探数据处理中的发展现状和发展趋势,分析了几个代表性的并行算法实例.这些结果表明,在拥有强大的并行机的基础上,基于并行计算开发环境(MPI和PVM等)设计高效的并行算法,通过分配合理的并行粒度、通信开销、负载平衡等执行高效的并行计算,可以有效加快处理速度、降低成本.目前,并行算法在地震数据处理中应用已较为成熟,近年来向更实用的基于PC机群的并行技术发展.然而,在非地震方法中,并行算法应用较少见文献报道,研究尚处于初级研究阶段.在大地电磁的二维和三维正、反演问题上,并行计算技术逐渐得到越来越多关注和重视.随着资源和能源需求的增长,地球物理勘探向深度和广度快速发展,大幅增长的数据量使得高性能并行计算机和高效的并行算法在勘探地球物理学中的发展和应用将占据愈来愈重要的地位.     

多维地震激励下考虑构件滞回性能的输电塔倒塌分析

本文基于角钢新型非线性材料本构模型对多维地震激励下输电塔倒塌破坏进行模拟研究。基于ABAQUS中RIKS算法得到不同长细比角钢的屈曲承载力,并通过承载力试验验证有限元分析结果。基于角钢滞回性能试验结果,采用Fortran语言编制角钢新型非线性材料本构模型,并与试验结果对比。建立输电塔三维有限元模型,采用动力显式分析方法,对多维地震激励下输电塔倒塌进行模拟,总结输电塔的极限承载力、杆件屈曲情况和倒塌位置。研究结果可为多维地震激励下输电塔抗倒塌设计提供参考。     

ParBreZo: A parallel,unstructured grid,Godunov-type,shallow-water code for high-resolution flood inundation modeling at the regional scale

Topographic data are increasingly available at high resolutions (<10 m) over large spatial extents to support detailed flood inundation modeling and loss estimation analyses required for flood risk management. This paper describes ParBreZo, the parallel implementation of a two-dimensional, Godunov-type, shallow-water code, to address the computational demand of high-resolution flood modeling at the regional scale (10²–10⁴ km²). A systematic approach to unstructured grid partitioning (domain decomposition) is presented, and the Single Process Multiple Data (SPMD) paradigm of distributed-memory parallelism is implemented so the code can be executed on computer clusters with distributed memory, shared memory, or some combination of the two (now common with multi-core architectures). In a fully-wetted, load-balanced test problem, the code scales very well with a parallel efficiency of close to 100% on up to 512 processes (maximum tested). A weighted grid partitioning is used to partially address the load balancing challenge posed by partially wetted domains germane to flooding applications, where the flood extent varies over time, while the partitioning remains static. An urban dam-break flood test problem shows that weighted partitions achieve a parallel efficiency exceeding 70% using up to 48 processes. This corresponds to a 97% reduction in execution time so results are obtained in a matter of minutes, which is attractive for routine engineering analyses. A hurricane storm surge test problem shows that a 10 m resolution, 12 h inundation forecast for a 40 km length of coastline can be completed in under 2 h using 512 processors. Hence, if coupled to a hurricane forecast system capable of resolving storm surge, inundation forecasts could be made at 10 m resolution with at least a 10 h lead time.     

基于Abaqus软件的并行计算集群平台构建与优化方法

根据有限元显式算法和隐式算法的特点,研究了岩土工程动力分析并行计算集群系统的硬件要求、集群系统的构建方法,构建了基于EM64T硬件构架、双路Intel Xeon处理器、Linux操作系统和64位Abaqus软件的32CPU并行计算集群平台,测试了存储子系统对集群性能的影响,比较了两种千兆以太网络作为、集群子网络的性能优化方法。以地下结构的地震反应分析为例,测试了优化前后该集群系统的计算速度,发现两种以太网络性能优化方法都可以有效提高集群计算速度。列举了该集群系统在深水桥梁基础流固耦合动力分析、地下结构地震反应分析和快速轨道交通环境振动分析中的应用,显示了该集群在显式算法、隐式算法及小规模、大规模数值计算问题中的并行计算效率,证明所构建的Abaqus数值模拟并行计算集群平台能够满足计算规模、计算精度和时效性的要求。     

An application of Karmarkar's interior-point linear programming algorithm for multi-reservoir operations optimization

Optimization of multi-reservoir systems operations is typically a very large scale optimization problem. The following are the three types of optimization problems solved using linear programming (LP): (i) deterministic optimization for multiple periods involving fine stage intervals, for example, from an hour to a week (ii) implicit stochastic optimization using multiple years of inflow data, and (iii) explicit stochastic optimization using probability distributions of inflow data. Until recently, the revised simplex method has been the most efficient solution method available for solving large scale LP problems. In this paper, we show that an implementation of the Karmarkar's interior-point LP algorithm with a newly developed stopping criterion solves optimization problems of large multi-reservoir operations more efficiently than the simplex method. For example, using a Micro VAX II minicomputer, a 40 year, monthly stage, two-reservoir system optimization problem is solved 7.8 times faster than the advanced simplex code in MINOS 5.0. The advantage of this method is expected to be greater as the size of the problem grows from two reservoirs to multiples of reservoirs. This paper presents the details of the implementation and testing and in addition, some other features of the Karmarkar's algorithm which makes it a valuable optimization tool are illuminated.     

An application of Karmarkar's interior-point linear programming algorithm for multi-reservoir operations optimization

Optimization of multi-reservoir systems operations is typically a very large scale optimization problem. The following are the three types of optimization problems solved using linear programming (LP): (i) deterministic optimization for multiple periods involving fine stage intervals, for example, from an hour to a week (ii) implicit stochastic optimization using multiple years of inflow data, and (iii) explicit stochastic optimization using probability distributions of inflow data. Until recently, the revised simplex method has been the most efficient solution method available for solving large scale LP problems. In this paper, we show that an implementation of the Karmarkar's interior-point LP algorithm with a newly developed stopping criterion solves optimization problems of large multi-reservoir operations more efficiently than the simplex method. For example, using a Micro VAX II minicomputer, a 40 year, monthly stage, two-reservoir system optimization problem is solved 7.8 times faster than the advanced simplex code in MINOS 5.0. The advantage of this method is expected to be greater as the size of the problem grows from two reservoirs to multiples of reservoirs. This paper presents the details of the implementation and testing and in addition, some other features of the Karmarkar's algorithm which makes it a valuable optimization tool are illuminated.     

Planning water resources management systems using a fuzzy-boundary interval-stochastic programming method

In this study, a fuzzy-boundary interval-stochastic programming (FBISP) method is developed for planning water resources management systems under uncertainty. The developed FBISP method can deal with uncertainties expressed as probability distributions and fuzzy-boundary intervals. With the aid of an interactive algorithm woven with a vertex analysis, solutions for FBISP model under associated α-cut levels can be generated by solving a set of deterministic submodels. The related probability and possibility information can also be reflected in the solutions for the objective function value and decision variables. The developed FBISP is also applied to water resources management and planning within a multi-reservoir system. Various policy scenarios that are associated with different levels of economic consequences when the pre-regulated water-allocation targets are violated are analyzed. The results obtained are useful for generating a range of decision alternatives under various system conditions, and thus helping decision makers to identify desired water resources management policies under uncertainty.     

An explicit finite element－finite difference method for analyzing the effect of visco－elastic local topography on the earthquake motion

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