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Turn MKL off by default. Add section on performance to INSTALL.md

release/4.3a0
chrisbeall 2019-03-12 09:22:09 -07:00
parent 400be7f5d4
commit e24b402db4
2 changed files with 33 additions and 14 deletions
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10
CMakeLists.txt
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@ -61,8 +61,8 @@ option(GTSAM_POSE3_EXPMAP "Enable/Disable using Pose3::EXPMAP as the defau
option(GTSAM_ROT3_EXPMAP "Ignore if GTSAM_USE_QUATERNIONS is OFF (Rot3::EXPMAP by default). Otherwise, enable Rot3::EXPMAP, or if disabled, use Rot3::CAYLEY." OFF)
option(GTSAM_ENABLE_CONSISTENCY_CHECKS "Enable/Disable expensive consistency checks" OFF)
option(GTSAM_WITH_TBB "Use Intel Threaded Building Blocks (TBB) if available" ON)
option(GTSAM_WITH_EIGEN_MKL "Eigen will use Intel MKL if available" ON)
option(GTSAM_WITH_EIGEN_MKL_OPENMP "Eigen, when using Intel MKL, will also use OpenMP for multithreading if available" ON)
option(GTSAM_WITH_EIGEN_MKL "Eigen will use Intel MKL if available" OFF)
option(GTSAM_WITH_EIGEN_MKL_OPENMP "Eigen, when using Intel MKL, will also use OpenMP for multithreading if available" OFF)
option(GTSAM_THROW_CHEIRALITY_EXCEPTION "Throw exception when a triangulated point is behind a camera" ON)
option(GTSAM_BUILD_PYTHON "Enable/Disable building & installation of Python module" OFF)
option(GTSAM_ALLOW_DEPRECATED_SINCE_V4 "Allow use of methods/functions deprecated in GTSAM 4" ON)
@ -563,12 +563,6 @@ message(STATUS "==============================================================="
if(GTSAM_WITH_TBB AND NOT TBB_FOUND)
message(WARNING "TBB was not found - this is ok, but note that GTSAM parallelization will be disabled. Set GTSAM_WITH_TBB to 'Off' to avoid this warning.")
endif()
if(GTSAM_WITH_EIGEN_MKL AND NOT MKL_FOUND)
message(WARNING "MKL was not found - this is ok, but note that MKL yields better performance. Set GTSAM_WITH_EIGEN_MKL to 'Off' to disable this warning.")
endif()
if(GTSAM_WITH_EIGEN_MKL_OPENMP AND NOT OPENMP_FOUND AND MKL_FOUND)
message(WARNING "Your compiler does not support OpenMP - this is ok, but performance may be improved with OpenMP. Set GTSAM_WITH_EIGEN_MKL_OPENMP to 'Off' to avoid this warning.")
endif()
if(GTSAM_BUILD_PYTHON AND GTSAM_PYTHON_WARNINGS)
message(WARNING "${GTSAM_PYTHON_WARNINGS}")
endif()

37
INSTALL.md
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@ -23,18 +23,22 @@ $ make install
disable the CMake flag GTSAM_WITH_TBB (enabled by default). On Ubuntu, TBB
may be installed from the Ubuntu repositories, and for other platforms it
may be downloaded from https://www.threadingbuildingblocks.org/
- GTSAM may be configured to use MKL by toggling `GTSAM_WITH_EIGEN_MKL` and
`GTSAM_WITH_EIGEN_MKL_OPENMP` to `ON`; however, best performance is usually
achieved with MKL disabled. We therefore advise you to benchmark your problem
before using MKL.
Tested compilers:
- GCC 4.2-4.7
- OSX Clang 2.9-5.0
- OSX GCC 4.2
- MSVC 2010, 2012
- GCC 4.2-7.3
- OS X Clang 2.9-10.0
- OS X GCC 4.2
- MSVC 2010, 2012, 2017
Tested systems:
- Ubuntu 11.04 - 18.04
- MacOS 10.6 - 10.9
- Ubuntu 16.04 - 18.04
- MacOS 10.6 - 10.14
- Windows 7, 8, 8.1, 10
Known issues:
@ -134,6 +138,27 @@ MEX_COMMAND: Path to the mex compiler. Defaults to assume the path is included i
$MATLABROOT can be found by executing the command `matlabroot` in MATLAB
## Performance
Here are some tips to get the best possible performance out of GTSAM.
1. Build in `Release` mode. GTSAM will run up to 10x faster compared to `Debug` mode.
2. Enable TBB. On modern processors with multiple cores, this can easily speed up
optimization by 30-50%. Please note that this may not be true for very small
problems where the overhead of dispatching work to multiple threads outweighs
the benefit. We recommend that you benchmark your problem with/without TBB.
3. Add `-march=native` to `GTSAM_CMAKE_CXX_FLAGS`. A performance gain of
25-30% can be expected on modern processors. Note that this affects the portability
of your executable. It may not run when copied to another system with older/different
processor architecture.
Also note that all dependent projects *must* be compiled with the same flag, or
seg-faults and other undefined behavior may result.
4. Enable MKL. Please note that our benchmarks have shown that this helps only
in very limited cases, and actually hurts performance in the usual case. We therefore
recommend that you do *not* enable MKL, unless you have benchmarked it on
your problem and have verified that it improves performance.
## Debugging tips
Another useful debugging symbol is _GLIBCXX_DEBUG, which enables debug checks and safe containers in the standard C++ library and makes problems much easier to find.