lect07-petsc-cactus - Notes MPI project due tomorrow 6PM...

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CMSC 714 Lecture 7 PETSc and Cactus Alan Sussman 2 CMSC 714 - Alan Sussman Notes ! MPI project due tomorrow, 6PM – via email of 1 gzipped tar file – Questions? ! OpenMP project posted Thursday ! No class Thursday - holiday 3 CMSC 714 - Alan Sussman PETSc ! Portable, Extensible Toolkit for Scientific Computation ! Library to encapsulate commonly used functions and data structures for numerically solving partial differential equations ! Targeted at message passing for scalability, but hides it (mostly) from application ! Uses object-oriented programming techniques – Data encapsulation – Polymorphism – Inheritance – but implemented in C, so no compiler support ! Essentially SPMD style programming, but w/o explicit message passing 4 6 guiding principles ! For performance – overlap communication and computation – determine details of repeated communication patterns, and optimize message passing across multiple calls (inspector/ executor model) – allow user to decide when communication occurs (if needed) – allow user to aggregate data for later communication ! For ease of use – allow user to work on distributed objects (arrays) without knowing which processor owns which data elements – manage communication at higher levels, on objects, instead of directly using message passing CMSC 714 - Alan Sussman
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5 Distributed Objects ! Low level data structures – Vectors – Matrices – Index Sets ! Low level algorithms – Create and assemble a vector or matrix – vector scatter/ gather, sparse matrix examples in paper ! Higher level algorithms – PDE solvers – Linear and non-linear equation solvers – Time steppers – Preconditioners ! All functions take an MPI_Comm as an argument CMSC 714 - Alan Sussman 6 Six Guiding Principles (again) ! Managing communication within higher level data structures and algorithms
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lect07-petsc-cactus - Notes MPI project due tomorrow 6PM...

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