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## Examples 84 85libCEED comes with several examples of its usage, ranging from standalone C 86codes in the `/examples/ceed` directory to examples based on external packages, 87such as MFEM, PETSc and Nek5000. 88 89To build the examples, set the `MFEM_DIR`, `PETSC_DIR` and `NEK5K_DIR` variables 90and run: 91 92```console 93# libCEED examples on CPU and GPU 94cd examples/ceed 95make 96./ex1 -ceed /cpu/self 97./ex1 -ceed /gpu/occa 98cd ../.. 99 100# MFEM+libCEED examples on CPU and GPU 101cd examples/mfem 102make 103./bp1 -ceed /cpu/self -no-vis 104./bp1 -ceed /gpu/occa -no-vis 105cd ../.. 106 107# PETSc+libCEED examples on CPU and GPU 108cd examples/petsc 109make 110./bp1 -ceed /cpu/self 111./bp1 -ceed /gpu/occa 112cd ../.. 113 114# Nek+libCEED examples on CPU and GPU 115cd examples/nek5000 116./make-nek-examples.sh 117./run-nek-example.sh -ceed /cpu/self -b 3 118./run-nek-example.sh -ceed /gpu/occa -b 3 119cd ../.. 120``` 121 122The above code assumes a GPU-capable machine enabled in the OCCA 123backend. Depending on the available backends, other Ceed resource specifiers can 124be provided with the `-ceed` option, for example: 125 126| CEED resource (`-ceed`) | Backend | 127| :----------------------- | :------------------------------------------------ | 128| `/cpu/self/avx` | Vectorized blocked implementation | 129| `/cpu/self/blocked` | Serial blocked implementation | 130| `/cpu/self/ref` | Serial reference implementation | 131| `/cpu/self/tmpl` | Backend template, dispatches to /cpu/self/blocked | 132| `/cpu/occa` | Serial OCCA kernels | 133| `/gpu/occa` | CUDA OCCA kernels | 134| `/omp/occa` | OpenMP OCCA kernels | 135| `/ocl/occa` | OpenCL OCCA kernels | 136| `/gpu/magma` | CUDA MAGMA kernels | 137 138## Install 139 140To install libCEED, run 141 142 make install prefix=/usr/local 143 144or (e.g., if creating packages), 145 146 make install prefix=/usr DESTDIR=/packaging/path 147 148Note that along with the library, libCEED installs kernel sources, e.g. OCCA 149kernels are installed in `$prefix/lib/okl`. This allows the OCCA backend to 150build specialized kernels at run-time. In a normal setting, the kernel sources 151will be found automatically (relative to the library file `libceed.so`). 152However, if that fails (e.g. if `libceed.so` is moved), one can copy (cache) the 153kernel sources inside the user OCCA directory, `~/.occa` using 154 155 $(OCCA_DIR)/bin/occa cache ceed $(CEED_DIR)/lib/okl/*.okl 156 157This will allow OCCA to find the sources regardless of the location of the CEED 158library. One may occasionally need to clear the OCCA cache, which can be accomplished 159by removing the `~/.occa` directory or by calling `$(OCCA_DIR)/bin/occa clear -a`. 160 161### pkg-config 162 163In addition to library and header, libCEED provides a [pkg-config][pkg-config1] 164file that can be used to easily compile and link. [For example][pkg-config2], if 165`$prefix` is a standard location or you set the environment variable 166`PKG_CONFIG_PATH`, 167 168 cc `pkg-config --cflags --libs ceed` -o myapp myapp.c 169 170will build `myapp` with libCEED. This can be used with the source or 171installed directories. Most build systems have support for pkg-config. 172 173## Contact 174 175You can reach the libCEED team by emailing [ceed-users@llnl.gov](mailto:ceed-users@llnl.gov) 176or by leaving a comment in the [issue tracker](https://github.com/CEED/libCEED/issues). 177 178## Copyright 179 180The following copyright applies to each file in the CEED software suite, unless 181otherwise stated in the file: 182 183> Copyright (c) 2017, Lawrence Livermore National Security, LLC. Produced at the 184> Lawrence Livermore National Laboratory. LLNL-CODE-734707. All Rights reserved. 185 186See files LICENSE and NOTICE for details. 187 188[ceed-soft]: http://ceed.exascaleproject.org/software/ 189[ecp]: https://exascaleproject.org/exascale-computing-project 190[pkg-config1]: https://en.wikipedia.org/wiki/Pkg-config 191[pkg-config2]: https://people.freedesktop.org/~dbn/pkg-config-guide.html#faq 192
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