Automated adjoints: how much do we really know about the source of the Indian Ocean Tsunami?

自动伴随：我们对印度洋海啸的根源到底了解多少？

• 批准号: NE/I001360/1
• 负责人: David Ham
• 金额: $ 7.55万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI001360%2F1
• 关键词: Automated; adjoints; how; much; do

Tsunamis are one of the most rapid and destructive of the geohazards which humanity faces and the Indian Ocean Tsunami of 26 December 2004 was the most powerful and destructive in recent history. In the intervening five years, much scientific effort has been expended attempting to understand the source and propagation of the tsunami. In many cases, hypotheses about the source region of the tsunami, which have been derived from geological, seismic and GPS data, have been tested by running a numerical ocean model starting from that source and comparing the results to tide gauge data and satellite altimetry taken during the actual tsunami event. These studies are an important contribution to our understanding of this devastating event, but they miss one important question: to what extent do the observations constrain the source region or could there be important differences in the source region which are not detectable in the relatively small number of observations we have to compare with? One reason that the existing studies have generally not addressed this problem is that studying the sensitivity of the model outputs to the model inputs, which is the essence of the question here, requires the use of an adjoint, or inverse, model. Producing forward ocean models is already a significant research task and producing a correct and matching adjoint model is very difficult and the resulting model system is typically very expensive in processor time to run. This project will employ exciting new software and hardware technology to vastly simplify the process of producing an adjoint model and deliver the performance increases needed to make adjoint problems tractable. The software technology in question is automatic code generation. In this approach the mathematical formulation of the finite element problem is automatically converted into highly efficient computer code. This dramatically reduces both developer effort and the incidence of code bugs. The novel aspect here will be to use this high level mathematical formulation to automatically generate the adjoint formulation, thereby avoiding the difficulty of building two models and ensuring consistency between forward and adjoint models. The novel hardware technology is graphical processing units (GPUs). Initial studies at Imperial College have indicated that automatically generated model code for GPUs can run more than twenty times faster than the equivalent code for ordinary processors. This combination of hardware and software will result in a step-change in the ease of development and the cost of running adjoint tsunami models. The resulting model will be used to conduct the missing sensitivity analysis of a number of the published tsunami source scenarios and will thereby enable us to answer the question: 'how much do we really know about the source of the Indian Ocean Tsunami?'.

海啸是人类面临的最迅速和最具破坏性的地质灾害之一，2004年12月26日的印度洋海啸是近代历史上最强大和最具破坏性的。在此期间的五年里，人们花费了大量的科学努力，试图了解海啸的来源和传播。在许多情况下，根据地质、地震和全球定位系统数据得出的关于海啸源区的假设，通过从该来源开始运行一个数值海洋模型，并将结果与实际海啸事件期间的验潮数据和卫星测高数据进行比较，得到了检验。这些研究对我们理解这一毁灭性事件做出了重要贡献，但它们忽略了一个重要问题：观测在多大程度上限制了源区，或者在相对较少的观测中无法检测到的源区中是否存在重要差异？现有的研究通常没有解决这个问题的一个原因是，研究模型输出对模型输入的敏感性，这是这里问题的本质，需要使用伴随或逆模型。产生前向海洋模型已经是一项重要的研究任务，并且产生正确和匹配的伴随模型是非常困难的，并且所产生的模型系统通常在处理器时间上运行是非常昂贵的。该项目将采用令人兴奋的新软件和硬件技术，大大简化了生成伴随模型的过程，并提供使伴随问题易于处理所需的性能提升。所讨论的软件技术是自动代码生成。在这种方法中，有限元问题的数学公式被自动转换成高效的计算机代码。这大大减少了开发人员的工作量和代码错误的发生率。这里的新颖之处将是使用这种高级数学公式来自动生成伴随公式，从而避免构建两个模型的困难，并确保前向模型和伴随模型之间的一致性。新的硬件技术是图形处理单元（GPU）。帝国理工学院的初步研究表明，自动生成的GPU模型代码可以比普通处理器的等效代码快20倍以上。这种硬件和软件的结合将使开发的容易程度和运行伴随海啸模型的成本发生阶跃变化。由此产生的模型将被用来进行一些已公布的海啸源情景的缺失敏感性分析，从而使我们能够回答这样一个问题：“我们对印度洋海啸的来源到底了解多少？”'.

项目成果

AUTOMATED DERIVATION OF THE ADJOINT OF HIGH-LEVEL TRANSIENT FINITE ELEMENT PROGRAMS

• DOI: 10.1137/120873558
• 发表时间: 2013-01-01
• 期刊: SIAM JOURNAL ON SCIENTIFIC COMPUTING
• 影响因子: 3.1
• 作者: Farrell, P. E.;Ham, D. A.;Rognes, M. E.
• 通讯作者: Rognes, M. E.