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` | Serial reference implementation | 90| `/cpu/self/ref/blocked` | Blocked refrence implementation | 91| `/cpu/self/memcheck` | Memcheck backend, undefined value checks | 92| `/cpu/self/opt/serial` | Serial optimized C implementation | 93| `/cpu/self/opt/blocked` | Blocked optimized C implementation | 94| `/cpu/self/avx/serial` | Serial AVX implementation | 95| `/cpu/self/avx/blocked` | Blocked AVX implementation | 96| `/cpu/self/xsmm/serial` | Serial LIBXSMM implementation | 97| `/cpu/self/xsmm/blocked` | Blocked LIBXSMM implementation | 98| `/cpu/occa` | Serial OCCA kernels | 99| `/gpu/occa` | CUDA OCCA kernels | 100| `/omp/occa` | OpenMP OCCA kernels | 101| `/ocl/occa` | OpenCL OCCA kernels | 102| `/gpu/cuda/ref` | Reference pure CUDA kernels | 103| `/gpu/cuda/reg` | Pure CUDA kernels using one thread per element | 104| `/gpu/cuda/shared` | Optimized pure CUDA kernels using shared memory | 105| `/gpu/cuda/gen` | Optimized pure CUDA kernels using code generation | 106| `/gpu/magma` | CUDA MAGMA kernels | 107 108The `/cpu/self/*/serial` backends process one element at a time and are intended for meshes 109with a smaller number of high order elements. The `/cpu/self/*/blocked` backends process 110blocked batches of eight interlaced elements and are intended for meshes with higher numbers 111of elements. 112 113The `/cpu/self/ref/*` backends are written in pure C and provide basic functionality. 114 115The `/cpu/self/opt/*` backends are written in pure C and use partial e-vectors to improve performance. 116 117The `/cpu/self/avx/*` backends rely upon AVX instructions to provide vectorized CPU performance. 118 119The `/cpu/self/xsmm/*` backends rely upon the [LIBXSMM](http://github.com/hfp/libxsmm) package 120to provide vectorized CPU performance. If linking MKL and LIBXSMM is desired but 121the Makefile is not detecting `MKLROOT`, linking libCEED against MKL can be 122forced by setting the environment variable `MKL=1`. 123 124The `/cpu/self/memcheck/*` backends rely upon the [Valgrind](http://valgrind.org/) Memcheck tool 125to help verify that user QFunctions have no undefined values. To use, run your code with 126Valgrind and the Memcheck backends, e.g. `valgrind ./build/ex1 -ceed /cpu/self/ref/memcheck`. A 127'development' or 'debugging' version of Valgrind with headers is required to use this backend. 128This backend can be run in serial or blocked mode and defaults to running in the serial mode 129if `/cpu/self/memcheck` is selected at runtime. 130 131The `/*/occa` backends rely upon the [OCCA](http://github.com/libocca/occa) package to provide 132cross platform performance. 133 134The `/gpu/cuda/*` backends provide GPU performance strictly using CUDA. 135 136The `/gpu/magma` backend relies upon the [MAGMA](https://bitbucket.org/icl/magma) package. 137 138## Examples 139 140libCEED comes with several examples of its usage, ranging from standalone C 141codes in the `/examples/ceed` directory to examples based on external packages, 142such as MFEM, PETSc, and Nek5000. Nek5000 v18.0 or greater is required. 143 144To build the examples, set the `MFEM_DIR`, `PETSC_DIR` and `NEK5K_DIR` variables 145and run: 146 147```console 148# libCEED examples on CPU and GPU 149cd examples/ceed 150make 151./ex1 -ceed /cpu/self 152./ex1 -ceed /gpu/occa 153cd ../.. 154 155# MFEM+libCEED examples on CPU and GPU 156cd examples/mfem 157make 158./bp1 -ceed /cpu/self -no-vis 159./bp3 -ceed /gpu/occa -no-vis 160cd ../.. 161 162# Nek5000+libCEED examples on CPU and GPU 163cd examples/nek 164make 165./nek-examples.sh -e bp1 -ceed /cpu/self -b 3 166./nek-examples.sh -e bp3 -ceed /gpu/occa -b 3 167cd ../.. 168 169# PETSc+libCEED examples on CPU and GPU 170cd examples/petsc 171make 172./bps -problem bp1 -ceed /cpu/self 173./bps -problem bp2 -ceed /gpu/occa 174./bps -problem bp3 -ceed /cpu/self 175./bps -problem bp4 -ceed /gpu/occa 176./bps -problem bp5 -ceed /cpu/self 177./bps -problem bp6 -ceed /gpu/occa 178cd ../.. 179 180cd examples/navier-stokes 181make 182./navierstokes -ceed /cpu/self 183./navierstokes -ceed /gpu/occa 184cd ../.. 185``` 186 187The above code assumes a GPU-capable machine with the OCCA backend 188enabled. Depending on the available backends, other Ceed resource specifiers can 189be provided with the `-ceed` option. 190 191## Benchmarks 192 193A sequence of benchmarks for all enabled backends can be run using 194 195```console 196make benchmarks 197``` 198 199The results from the benchmarks are stored inside the `benchmarks/` directory 200and they can be viewed using the commands (requires python with matplotlib): 201 202```console 203cd benchmarks 204python postprocess-plot.py petsc-bps-bp1-*-output.txt 205python postprocess-plot.py petsc-bps-bp3-*-output.txt 206``` 207 208Using the `benchmarks` target runs a comprehensive set of benchmarks which may 209take some time to run. Subsets of the benchmarks can be run using the scripts in the `benchmarks` folder. 210 211For more details about the benchmarks, see 212[`benchmarks/README.md`](benchmarks/README.md) 213 214 215## Install 216 217To install libCEED, run 218 219 make install prefix=/usr/local 220 221or (e.g., if creating packages), 222 223 make install prefix=/usr DESTDIR=/packaging/path 224 225Note that along with the library, libCEED installs kernel sources, e.g. OCCA 226kernels are installed in `$prefix/lib/okl`. This allows the OCCA backend to 227build specialized kernels at run-time. In a normal setting, the kernel sources 228will be found automatically (relative to the library file `libceed.so`). 229However, if that fails (e.g. if `libceed.so` is moved), one can copy (cache) the 230kernel sources inside the user OCCA directory, `~/.occa` using 231 232 $(OCCA_DIR)/bin/occa cache ceed $(CEED_DIR)/lib/okl/*.okl 233 234This will allow OCCA to find the sources regardless of the location of the CEED 235library. One may occasionally need to clear the OCCA cache, which can be accomplished 236by removing the `~/.occa` directory or by calling `$(OCCA_DIR)/bin/occa clear -a`. 237 238### pkg-config 239 240In addition to library and header, libCEED provides a [pkg-config][pkg-config1] 241file that can be used to easily compile and link. [For example][pkg-config2], if 242`$prefix` is a standard location or you set the environment variable 243`PKG_CONFIG_PATH`, 244 245 cc `pkg-config --cflags --libs ceed` -o myapp myapp.c 246 247will build `myapp` with libCEED. This can be used with the source or 248installed directories. Most build systems have support for pkg-config. 249 250## Contact 251 252You can reach the libCEED team by emailing [ceed-users@llnl.gov](mailto:ceed-users@llnl.gov) 253or by leaving a comment in the [issue tracker](https://github.com/CEED/libCEED/issues). 254 255## Copyright 256 257The following copyright applies to each file in the CEED software suite, unless 258otherwise stated in the file: 259 260> Copyright (c) 2017, Lawrence Livermore National Security, LLC. Produced at the 261> Lawrence Livermore National Laboratory. LLNL-CODE-734707. All Rights reserved. 262 263See files LICENSE and NOTICE for details. 264 265[ceed-soft]: http://ceed.exascaleproject.org/software/ 266[ecp]: https://exascaleproject.org/exascale-computing-project 267[pkg-config1]: https://en.wikipedia.org/wiki/Pkg-config 268[pkg-config2]: https://people.freedesktop.org/~dbn/pkg-config-guide.html#faq 269
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