1# libCEED: the CEED API Library 2 3[](https://travis-ci.org/CEED/libCEED) 4[](https://opensource.org/licenses/BSD-2-Clause) 5[](https://codedocs.xyz/CEED/libCEED/) 6 7## Code for Efficient Extensible Discretization 8 9This repository contains an initial low-level API library for the efficient 10high-order discretization methods developed by the ECP co-design [Center for 11Efficient Exascale Discretizations (CEED)](http://ceed.exascaleproject.org). 12While our focus is on high-order finite elements, the approach is mostly 13algebraic and thus applicable to other discretizations in factored form, see the 14[API documentation](doc/libCEED.md). 15 16One of the challenges with high-order methods is that a global sparse matrix is 17no longer a good representation of a high-order linear operator, both with 18respect to the FLOPs needed for its evaluation, as well as the memory transfer 19needed for a matvec. Thus, high-order methods require a new "format" that still 20represents a linear (or more generally non-linear) operator, but not through a 21sparse matrix. 22 23The goal of libCEED is to propose such a format, as well as supporting 24implementations and data structures, that enable efficient operator evaluation 25on a variety of computational device types (CPUs, GPUs, etc.). This new operator 26description is based on algebraically [factored form](doc/libCEED.md), which is 27easy to incorporate in a wide variety of applications, without significant 28refactoring of their own discretization infrastructure. 29 30The repository is part of the [CEED software suite][ceed-soft], a collection of 31software benchmarks, miniapps, libraries and APIs for efficient exascale 32discretizations based on high-order finite element and spectral element methods. 33See http://github.com/ceed for more information and source code availability. 34 35The CEED research is supported by the [Exascale Computing Project][ecp] 36(17-SC-20-SC), a collaborative effort of two U.S. Department of Energy 37organizations (Office of Science and the National Nuclear Security 38Administration) responsible for the planning and preparation of a [capable 39exascale ecosystem](https://exascaleproject.org/what-is-exascale), including 40software, applications, hardware, advanced system engineering and early testbed 41platforms, in support of the nation’s exascale computing imperative. 42 43For more details on the CEED API see http://ceed.exascaleproject.org/ceed-code/. 44 45## Building 46 47The CEED library, `libceed`, is a C99 library with no external dependencies. It 48can be built using 49 50 make 51 52or, with optimization flags 53 54 make OPT='-O3 -march=skylake-avx512 -ffp-contract=fast' 55 56These optimization flags are used by all languages (C, C++, Fortran) and this 57makefile variable can also be set for testing and examples (below). 58 59## Testing 60 61The test suite produces [TAP](https://testanything.org) output and is run by: 62 63 make test 64 65or, using the `prove` tool distributed with Perl (recommended) 66 67 make prove 68 69## Examples 70 71libCEED comes with several examples of its usage, ranging from standalone C 72codes in the `/examples/ceed` directory to examples based on external packages, 73such as MFEM, PETSc and Nek5000. 74 75To build the examples, set the `MFEM_DIR`, `PETSC_DIR` and `NEK5K_DIR` variables 76and run: 77 78```console 79# libCEED examples on CPU and GPU 80cd examples/ceed 81make 82./ex1 -ceed /cpu/self 83./ex1 -ceed /gpu/occa 84cd ../.. 85 86# MFEM+libCEED examples on CPU and GPU 87cd examples/mfem 88make 89./bp1 -ceed /cpu/self -no-vis 90./bp1 -ceed /gpu/occa -no-vis 91cd ../.. 92 93# PETSc+libCEED examples on CPU and GPU 94cd examples/petsc 95make 96./bp1 -ceed /cpu/self 97./bp1 -ceed /gpu/occa 98cd ../.. 99 100# Nek+libCEED examples on CPU and GPU 101cd examples/nek5000 102./make-nek-examples.sh 103./run-nek-example.sh -ceed /cpu/self -b 3 104./run-nek-example.sh -ceed /gpu/occa -b 3 105cd ../.. 106``` 107 108The above code assumes a GPU-capable machine enabled in the OCCA 109backend. Depending on the available backends, other Ceed resource specifiers can 110be provided with the `-ceed` option, for example: 111 112CEED resource (`-ceed`) | Backend 113----------------------- | --------------------------------- 114`/cpu/self/opt` | Serial optimized implementation 115`/cpu/self/ref` | Serial reference implementation 116`/cpu/self/tmpl` | Backend template, dispatches to /cpu/self/opt 117`/cpu/occa` | Serial OCCA kernels 118`/gpu/occa` | CUDA OCCA kernels 119`/omp/occa` | OpenMP OCCA kernels 120`/ocl/occa` | OpenCL OCCA kernels 121`/gpu/magma` | CUDA MAGMA kernels 122 123## Install 124 125To install libCEED, run 126 127 make install prefix=/usr/local 128 129or (e.g., if creating packages), 130 131 make install prefix=/usr DESTDIR=/packaging/path 132 133Note that along with the library, libCEED installs kernel sources, e.g. OCCA 134kernels are installed in `$prefix/lib/okl`. This allows the OCCA backend to 135build specialized kernels at run-time. In a normal setting, the kernel sources 136will be found automatically (relative to the library file `libceed.so`). 137However, if that fails (e.g. if `libceed.so` is moved), one can copy (cache) the 138kernel sources inside the user OCCA directory, `~/.occa` using 139 140 $(OCCA_DIR)/bin/occa cache ceed $(CEED_DIR)/lib/okl/*.okl 141 142This will allow OCCA to find the sources regardless of the location of the CEED 143library. One may occasionally need to clear the OCCA cache, which can be accomplished 144by removing the `~/.occa` directory or by calling `$(OCCA_DIR)/bin/occa clear -a`. 145 146### pkg-config 147 148In addition to library and header, libCEED provides a [pkg-config][pkg-config1] 149file that can be used to easily compile and link. [For example][pkg-config2], if 150`$prefix` is a standard location or you set the environment variable 151`PKG_CONFIG_PATH`, 152 153 cc `pkg-config --cflags --libs ceed` -o myapp myapp.c 154 155will build `myapp` with libCEED. This can be used with the source or 156installed directories. Most build systems have support for pkg-config. 157 158## Contact 159 160You can reach the libCEED team by emailing [ceed-users@llnl.gov](mailto:ceed-users@llnl.gov) 161or by leaving a comment in the [issue tracker](https://github.com/CEED/libCEED/issues). 162 163## Copyright 164 165The following copyright applies to each file in the CEED software suite, unless 166otherwise stated in the file: 167 168> Copyright (c) 2017, Lawrence Livermore National Security, LLC. Produced at the 169> Lawrence Livermore National Laboratory. LLNL-CODE-734707. All Rights reserved. 170 171See files LICENSE and NOTICE for details. 172 173[ceed-soft]: http://ceed.exascaleproject.org/software/ 174[ecp]: https://exascaleproject.org/exascale-computing-project 175[pkg-config1]: https://en.wikipedia.org/wiki/Pkg-config 176[pkg-config2]: https://people.freedesktop.org/~dbn/pkg-config-guide.html#faq 177
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