Gen X: ExCALIBUR working group on Exascale continuum mechanics through code generation.

连续的物理过程渗透到我们社会、工业和自然界的方方面面。从飞机上的空气流动到移动电话信号的传播，再到制造过程中每一个点上化学成分的行为，连续介质力学是我们工业过程的核心。在医学上，心脏和大脑的电行为，血液和其他液体在体内的流动，以及使用各种扫描仪和探测器检测疾病，都是连续的机械过程。在自然界中，探测和了解地球的运动和组成使我们能够了解地震并寻找有价值的矿物，而对流体和电磁场复杂相互作用的深入了解使我们能够了解恒星、宇宙和我们在其中的位置。在所有这些情况下，以及更多的情况下，描述现象的数学方程是已知的，但解决方案非常罕见。科学和工程基本上依赖于计算机模拟来理解这些系统中的任何一个，并设计使用它们的设备和工艺。这些现象中的许多非常复杂，或者具有如此广泛的空间尺度，以至于现有的千万亿级计算机系统是科学进步的限制。此外，还需要超越单纯的模拟来模拟过程中的不确定性，找到最优解，或发现系统的多种可能结果。艾级计算的出现为解决这些限制提供了机会。然而，不断增长的计算规模，日益复杂的模拟算法，以及大规模计算产生的大量数据，不仅将使现有的模拟软件失效，而且将使现有的编写模拟软件的方法失效。X世代是一个项目，旨在确定对连续介质力学的大规模模拟软件的需求，并提供在未来五年内实现这一能力的具体方法。X世代的方法是超越仅仅编写代码，而是建立一个专门的模拟语言系统，使科学家和工程师能够通过编写数学这一科学语言来具体说明他们想要解决的问题和他们想要的算法。实际代码将由专业编译器自动生成，而不是手动编写。算法开发人员不会写一篇关于他们的新开发的论文，并希望模拟科学家找到时间为他们的特定问题编写代码，而是算法将以特定于领域的语言编码，并在其编译器中实现。然后，模拟科学家将能够直接访问算法，而无需编码。在数量级上，将所有模拟输出写入磁盘以供以后分析是不可能的。相反，在进行模拟时，必须对模拟数据进行处理、分析和可视化，并仅存储结果以供以后使用。X世代将为这一过程提供数学语言，这将使科学家或工程师能够简明扼要地指定要执行的分析，并相信结果将是有效和正确的。通过使科学家和工程师能够在更高的数学水平上工作，同时也能够访问比以前可能的更复杂的算法和特定于硬件的实现，X世代将使模拟科学更有能力和更有生产力。通过这种方式，X世代对于实现大规模计算的潜力，同时也最有效地利用研究资源至关重要。

Continuous physical processes pervade every aspect of our society,industry and the natural world. From the flow of air over an aircraftto the propagation of mobile phone signals, to the behaviour ofchemical components at every point of the manufacturing processes,continuum mechanics is at the heart of our industrial processes. Inmedicine, the electrical behaviour of the heart and brain, the flow ofblood and other fluids through the body, and the detection of disordersusing all manner of scanners and detectors are all continuum mechanicsprocesses. In the natural world, detecting and understanding themovement and composition of the Earth enable us to understandearthquakes and to hunt for valuable minerals, while advancedunderstanding of the complex interaction of fluids and electromagneticfields allows us to understand stars, the cosmos and our place in it.In all of these cases and many more beside, the mathematical equationsdescribing phenomena are known, but solutions very rarelyexist. Science and engineering are essentially dependent on computersimulation to understand any of these systems, and to design thedevices and processes which use them. Many of these phenomena are socomplex or have such a range of spatial scales that existing petascalecomputer systems are a limit on scientific advance. In addition, thereis a need to go beyond mere simulation to simulate the uncertainty inprocesses, find the optimal solution, or discover the multiplepossible outcomes of a system. The advent of exascale computingpresents the opportunity to address these limitations. However,increasing computational scale, increasingly complex simulationalgorithms, and the vast quantities of data produced by exascalecomputing will defeat not just existing simulation software, but alsoexisting ways of writing simulation software.Gen X is a project to establish the requirements for exascalesimulation software for continuum mechanics, and to provide a concreteway of achieving this capability within the next five years. The Gen Xapproach is to move beyond just writing code to a system of specialistsimulation languages which enable scientists and engineers to specifythe problem they want to solve and the algorithms they want by writingmathematics, the language of science. The actual code will beautomatically generated by specialist compilers rather thanhand-written. Rather than an algorithm developer writing a paper abouttheir new development and hoping that simulation scientists will findthe time to code it up for their specific problem, the algorithm willbe encoded in a domain specific language and implemented in itscompiler. The simulation scientist will then be able to access thealgorithm directly without recoding.At exascale, writing all the simulation outputs to disk for lateranalysis is impossible. Instead, simulation data must be processed,analysed and visualised as the simulation is conducted, and only theresults stored for later use. Gen X will provide mathematicallanguages for this process which will enable the scientist or engineerto concisely specify the analysis to be performed, and to haveconfidence that the resulting calculations will be both efficient andcorrect.By enabling scientists and engineers to work at a higher mathematicallevel while also accessing more sophisticated algorithms andhardware-specific implementations than previously possible, Gen X willmake simulation science both more capable and more productive. In thismanner, Gen X is essential to realising the potential of exascalecomputing while also making the most efficient use of researchresources.