Open Compute Stack (OpenCS) Overview. D.D. Nikolić Updated: 20 August 2018 DAE Tools Project,

Transcription

1 Open Compute Stack (OpenCS) Overview D.D. Nikolić Updated: 20 August 2018 DAE Tools Project,

2 What is OpenCS? A framework for: Platform-independent model specification 1. Equation-based modelling (large-scale ODE/DAE systems) 2. Parallel evaluation of equations 3. Model exchange 4. Parallel simulation on: - Shared memory systems - Distributed memory systems Multi-domain applications Free/Open source software Cross-platform Modelling Software generates Model structure Model equations Partition data Solver options Model structure Model equations Partition data Solver options Model structure Model equations Partition data Solver options N Simulation ODE/DAE sub-system 0 PE 0 Simulation ODE/DAE sub-system 1... PE 1 Simulation ODE/DAE sub-system N PE N MPI MPI MPI Infiniband / Gigabit ethernet Workstation Network File System Distributed Memory System

3 Use case scenarios OpenCS framework 1. Development of large-scale models (C++) 2. Parallel evaluation of model equations 3. Universal parallel simulations on shared and distributed memory systems 4. Model export from simulators for: - Model exchange - Benchmark between simulators - Benchmark between HPC systems (i.e. hybrid CPU+GPU and CPU+FPGA clusters) Simulators C++ Compute Stack Model Hardware CPU GPU FPGA Xeon Phi ODE/DAE Solver

4 What can be done with OpenCS? Model specification Direct implementation in C++ Modelling and Domain Specific Languages Modelica CAE Software DAE Tools C/C++ Fortran Directly create Export from 3 rd -party simulators AST AST FD/FV/FE Discretisation Operator overloading Model exchange OpenCS models stored as files in a platform-independent Internal data structures Internal data structures C source SpMV/SpMM Stencil codes Evaluation Tree Export simulator specific data structures binary format The OpenCS API: - Loading the models into a host - Interface to ODE/DAE solvers (i.e. evaluation of equations) ODE/DAE Solver ODE/DAE solver interface ODE/DAE solver interface Compute Stack Model

5 What can be done with OpenCS? Platform-independent description of model equations Reverse Polish (postfix) notation (Compute Stack) x evaluation context N v Evaluation using a Compute Stack Machine Advantages: Equations as an array of binary data Direct evaluation on all computing platforms random access data dx/dt N v y N d Compute Stack Machine result Specialised hardware for evaluation (i.e. FPGA) No additional processing nor compilation steps N cs opcode opcode opcode opcode data data data data compute stack (data stream)

6 What can be done with OpenCS? Multi-core CPU, Xeon Phi Parallel evaluation of model equations CSM CSM CSM CSM Systems of equations evaluated using the Compute Stack Evaluator interface: CSM CSM CSM CSM OpenMP for general purpose processors OpenMP (multi-core CPUs, Xeon Phi) OpenCL for: streaming processors (GPU, FPGA) heterogeneous systems (CPU+GPU/FPGA) OpenCL Compute Stack Machine kernels GPU, FPGA

7 What can be done with OpenCS? Parallel simulation on shared memory systems Multi-core CPU, Xeon Phi Single processing element CSM CSM CSM CSM Available computing hardware CSM CSM CSM CSM utilised for parallel evaluation of model equations: - Multi-core CPU, Xeon Phi Linear Solver Calls Evaluate derivatives (compute preconditioner) Compute Stack ODE/DAE Model Calls OpenMP OpenCL Compute Stack Machine kernels - GPU, FPGA - Heterogeneous systems i.e. CPU+GPU, CPU+FPGA Linear Algebra Solve linear system Calls ODE/DAE Solver Evaluate equations GPU, FPGA

8 What can be done with OpenCS? Linear Solver Compute Stack ODE/DAE Model Parallel simulation on distributed memory systems Multiple processing elements Software for simulation on shared memory systems as the main building block Partitioning using multiple balancing constraints Every processing element: Linear Algebra ODE/DAE sub-system 0 Linear Solver ODE/DAE Solver... Compute Stack ODE/DAE Model Interprocess Communication Processing Element 0 Infiniband / Gigabit ethernet - Integrates one ODE/DAE sub-system in time - Performs an inter-process data exchange Linear Algebra ODE/DAE Solver Interprocess Communication ODE/DAE sub-system N Processing Element N

9 OpenCS benefits A single software for numerical solution of any ODE/DAE system of any size on all platforms The model specification contains only the low-level model description (created from any software) The model specification stored as files in a platform-independent binary format Model equations specified in a platform independent way as an array of binary data Equations can be evaluated on virtually all computing devices (including heterogeneous systems) Switching to a different computing platform for evaluation of equations as an input parameter

10 The key OpenCS concepts Compute Stack: The Reverse Polish (postfix) notation expression stack to describe and store in computer memory equations of any type and any size Compute Stack Machine: A stack machine used to evaluate a single equation using LIFO queues Compute Stack Evaluator: Compute Stack Model: An interface for parallel evaluation of systems of equations Data structure that holds the low-level model specification Compute Stack Differential Equations Model: A common interface for ODE/DAE solvers for integration of ODE/DAE systems in time Compute Stack Simulator: Sequential/parallel simulator for general ODE/DAE systems Compute Stack Model Builder: A common interface for creation of ODE/DAE Compute Stack models