1# libCEED: the CEED API Library 2 3[](https://travis-ci.org/CEED/libCEED) 4[](https://codecov.io/gh/CEED/libCEED/) 5[](https://opensource.org/licenses/BSD-2-Clause) 6[](https://codedocs.xyz/CEED/libCEED/) 7 8## Code for Efficient Extensible Discretization 9 10This repository contains an initial low-level API library for the efficient 11high-order discretization methods developed by the ECP co-design [Center for 12Efficient Exascale Discretizations (CEED)](http://ceed.exascaleproject.org). 13While our focus is on high-order finite elements, the approach is mostly 14algebraic and thus applicable to other discretizations in factored form, as 15explained in the API documentation portion of the [Doxygen documentation](https://codedocs.xyz/CEED/libCEED/md_doc_libCEEDapi.html). 16 17One of the challenges with high-order methods is that a global sparse matrix is 18no longer a good representation of a high-order linear operator, both with 19respect to the FLOPs needed for its evaluation, as well as the memory transfer 20needed for a matvec. Thus, high-order methods require a new "format" that still 21represents a linear (or more generally non-linear) operator, but not through a 22sparse matrix. 23 24The goal of libCEED is to propose such a format, as well as supporting 25implementations and data structures, that enable efficient operator evaluation 26on a variety of computational device types (CPUs, GPUs, etc.). This new operator 27description is based on algebraically [factored form](https://codedocs.xyz/CEED/libCEED/md_doc_libCEEDapi.html), 28which is easy to incorporate in a wide variety of applications, without significant 29refactoring of their own discretization infrastructure. 30 31The repository is part of the [CEED software suite][ceed-soft], a collection of 32software benchmarks, miniapps, libraries and APIs for efficient exascale 33discretizations based on high-order finite element and spectral element methods. 34See http://github.com/ceed for more information and source code availability. 35 36The CEED research is supported by the [Exascale Computing Project][ecp] 37(17-SC-20-SC), a collaborative effort of two U.S. Department of Energy 38organizations (Office of Science and the National Nuclear Security 39Administration) responsible for the planning and preparation of a [capable 40exascale ecosystem](https://exascaleproject.org/what-is-exascale), including 41software, applications, hardware, advanced system engineering and early testbed 42platforms, in support of the nation’s exascale computing imperative. 43 44For more details on the CEED API see http://ceed.exascaleproject.org/ceed-code/. 45 46## Building 47 48The CEED library, `libceed`, is a C99 library with no external dependencies. It 49can be built using 50 51 make 52 53or, with optimization flags 54 55 make OPT='-O3 -march=skylake-avx512 -ffp-contract=fast' 56 57These optimization flags are used by all languages (C, C++, Fortran) and this 58makefile variable can also be set for testing and examples (below). 59 60The library attempts to automatically detect support for the AVX 61instruction set using gcc-style compiler options for the host. 62Support may need to be manually specified via 63 64 make AVX=1 65 66or 67 68 make AVX=0 69 70if your compiler does not support gcc-style options, if you are cross 71compiling, etc. 72 73## Testing 74 75The test suite produces [TAP](https://testanything.org) output and is run by: 76 77 make test 78 79or, using the `prove` tool distributed with Perl (recommended) 80 81 make prove 82 83## Backends 84 85There are multiple supported backends, which can be selected at runtime in the examples: 86 87| CEED resource | Backend | 88| :----------------------- | :------------------------------------------------ | 89| `/cpu/self/ref` | Serial reference implementation | 90| `/cpu/self/blocked` | Blocked refrence implementation | 91| `/cpu/self/tmpl` | Backend template, dispatches to /cpu/self/blocked | 92| `/cpu/self/avx` | Blocked AVX implementation | 93| `/cpu/self/xsmm/serial` | Serial LIBXSMM implementation | 94| `/cpu/self/xsmm/blocked` | Blocked LIBXSMM implementation | 95| `/cpu/occa` | Serial OCCA kernels | 96| `/gpu/occa` | CUDA OCCA kernels | 97| `/omp/occa` | OpenMP OCCA kernels | 98| `/ocl/occa` | OpenCL OCCA kernels | 99| `/gpu/cuda` | Pure CUDA kermels | 100| `/gpu/magma` | CUDA MAGMA kernels | 101 102The `/cpu/self/*/serial` backends process one element at a time and are intended for meshes 103with a smaller number of high order elements. The `/cpu/self/*/blocked` backends process 104blocked batches of eight interlaced elements and are intended for meshes with higher numbers 105of elements. 106 107The `/cpu/self/avx` backend relies upon AVX instructions to provide vectorized CPU performance. 108 109The `/cpu/self/xsmm/*` backends relies upon the [LIBXSMM](http://github.com/hfp/libxsmm) package 110to provide vectorized CPU performance. 111 112The `/*/occa` backends rely upon the [OCCA](http://github.com/libocca/occa) package to provide 113cross platform performance. 114 115The `/gpu/cuda` backend provides GPU performance strictly using CUDA. 116 117The `/gpu/magma` backend relies upon the [MAGMA](https://bitbucket.org/icl/magma) package. 118 119## Examples 120 121libCEED comes with several examples of its usage, ranging from standalone C 122codes in the `/examples/ceed` directory to examples based on external packages, 123such as MFEM, PETSc, and Nek5000. Nek5000 v18.0 or greater is required. 124 125To build the examples, set the `MFEM_DIR`, `PETSC_DIR` and `NEK5K_DIR` variables 126and run: 127 128```console 129# libCEED examples on CPU and GPU 130cd examples/ceed 131make 132./ex1 -ceed /cpu/self 133./ex1 -ceed /gpu/occa 134cd ../.. 135 136# MFEM+libCEED examples on CPU and GPU 137cd examples/mfem 138make 139./bp1 -ceed /cpu/self -no-vis 140./bp1 -ceed /gpu/occa -no-vis 141cd ../.. 142 143# PETSc+libCEED examples on CPU and GPU 144cd examples/petsc 145make 146./bp1 -ceed /cpu/self 147./bp1 -ceed /gpu/occa 148cd ../.. 149 150# Nek+libCEED examples on CPU and GPU 151cd examples/nek5000 152./make-nek-examples.sh 153./run-nek-example.sh -ceed /cpu/self -b 3 154./run-nek-example.sh -ceed /gpu/occa -b 3 155cd ../.. 156``` 157 158The above code assumes a GPU-capable machine with the OCCA backend 159enabled. Depending on the available backends, other Ceed resource specifiers can 160be provided with the `-ceed` option. 161 162## Benchmarks 163 164A sequence of benchmarks for all enabled backends can be run using 165 166```console 167make benchmarks 168``` 169 170The results from the benchmarks are stored inside the `benchmarks/` directory 171and they can be viewed using the commands (requires python with matplotlib): 172 173```console 174cd benchmarks 175python postprocess-plot.py petsc-bp1-*-output.txt 176python postprocess-plot.py petsc-bp3-*-output.txt 177``` 178 179Using the `benchmarks` target runs a comprehensive set of benchmarks which may 180take some time to run. Subsets of the benchmarks can be run using targets such 181as `make bench-petsc-bp1`, or `make bench-petsc-bp3`. 182 183For more details about the benchmarks, see 184[`benchmarks/README.md`](benchmarks/README.md) 185 186 187## Install 188 189To install libCEED, run 190 191 make install prefix=/usr/local 192 193or (e.g., if creating packages), 194 195 make install prefix=/usr DESTDIR=/packaging/path 196 197Note that along with the library, libCEED installs kernel sources, e.g. OCCA 198kernels are installed in `$prefix/lib/okl`. This allows the OCCA backend to 199build specialized kernels at run-time. In a normal setting, the kernel sources 200will be found automatically (relative to the library file `libceed.so`). 201However, if that fails (e.g. if `libceed.so` is moved), one can copy (cache) the 202kernel sources inside the user OCCA directory, `~/.occa` using 203 204 $(OCCA_DIR)/bin/occa cache ceed $(CEED_DIR)/lib/okl/*.okl 205 206This will allow OCCA to find the sources regardless of the location of the CEED 207library. One may occasionally need to clear the OCCA cache, which can be accomplished 208by removing the `~/.occa` directory or by calling `$(OCCA_DIR)/bin/occa clear -a`. 209 210### pkg-config 211 212In addition to library and header, libCEED provides a [pkg-config][pkg-config1] 213file that can be used to easily compile and link. [For example][pkg-config2], if 214`$prefix` is a standard location or you set the environment variable 215`PKG_CONFIG_PATH`, 216 217 cc `pkg-config --cflags --libs ceed` -o myapp myapp.c 218 219will build `myapp` with libCEED. This can be used with the source or 220installed directories. Most build systems have support for pkg-config. 221 222## Contact 223 224You can reach the libCEED team by emailing [ceed-users@llnl.gov](mailto:ceed-users@llnl.gov) 225or by leaving a comment in the [issue tracker](https://github.com/CEED/libCEED/issues). 226 227## Copyright 228 229The following copyright applies to each file in the CEED software suite, unless 230otherwise stated in the file: 231 232> Copyright (c) 2017, Lawrence Livermore National Security, LLC. Produced at the 233> Lawrence Livermore National Laboratory. LLNL-CODE-734707. All Rights reserved. 234 235See files LICENSE and NOTICE for details. 236 237[ceed-soft]: http://ceed.exascaleproject.org/software/ 238[ecp]: https://exascaleproject.org/exascale-computing-project 239[pkg-config1]: https://en.wikipedia.org/wiki/Pkg-config 240[pkg-config2]: https://people.freedesktop.org/~dbn/pkg-config-guide.html#faq 241
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