Project details for MLPACK

Logo MLPACK 1.0.0

by rcurtin - February 3, 2012, 11:00:26 CET [ Project Homepage BibTeX BibTeX for corresponding Paper Download ]

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MLPACK is a new, state-of-the-art, scalable C++ machine learning library, released in early December 2011. Its aim is to make large-scale machine learning possible for novice users by means of a simple, consistent API, while simultaneously exploiting C++ language features to provide maximum performance and maximum flexibility for expert users. MLPACK provides many cutting-edge algorithms,including---but not limited to---tree-based k-nearest-neighbors, fast hierarchical clustering, MVU (maximum variance unfolding) with LRSDP, RADICAL (ICA),and HMMs. Each of these algorithms is highly flexible and configurable, and all ofthem can be configured to use sparse matrices for datasets. Benchmarks are shown to prove that MLPACK scales more effectively than competing toolkits. Future plans for MLPACK include support for parallel algorithms, support for disk-based datasets, as well as the implementation of a large collection ofcutting-edge algorithms. More information on MLPACK is available at theproject's website, which is located at

Changes to previous version:

Yet another announcement on

BibTeX Entry: Download
Corresponding Paper BibTeX Entry: Download
URL: Project Homepage
Supported Operating Systems: Platform Independent
Data Formats: Plain Ascii, Ascii, Txt, Bin, Csv, Xml
Tags: Gmm, Hmm, Machine Learning, Sparse, Dual Tree, Fast, Scalable, Tree
Archive: download here

Other available revisons

Version Changelog Date
  • Fix CMake to properly detect when MKL is being used with Armadillo.
  • Minor parameter handling fixes to mlpack_logistic_regression.
  • Properly install arma_config.hpp.
  • Memory handling fixes for Hoeffding tree code.
  • Add functions that allow changing training-time parameters to HoeffdingTree class.
  • Fix infinite loop in sparse coding test.
  • Documentation spelling fixes.
  • Properly handle covariances for Gaussians with large condition number, preventing GMMs from filling with NaNs during training (and also HMMs that use GMMs).
  • CMake fixes for finding LAPACK and BLAS as Armadillo dependencies when ATLAS is used.
  • CMake fix for projects using mlpack's CMake configuration from elsewhere.
March 3, 2016, 18:52:03
  • Removed overclustering support from k-means because it is not well-tested, may be buggy, and is (I think) unused. If this was support you were using, open a bug or get in touch with us; it would not be hard for us to reimplement it.
  • Refactored KMeans to allow different types of Lloyd iterations.
  • Added implementations of k-means: Elkan's algorithm, Hamerly's algorithm, Pelleg-Moore's algorithm, and the DTNN (dual-tree nearest neighbor) algorithm.
  • Significant acceleration of LRSDP via the use of accu(a % b) instead of trace(a * b).
  • Added MatrixCompletion class (matrix_completion), which performs nuclear norm minimization to fill unknown values of an input matrix.
  • No more dependence on Boost.Random; now we use C++11 STL random support.
  • Add softmax regression, contributed by Siddharth Agrawal and QiaoAn Chen.
  • Changed NeighborSearch, RangeSearch, FastMKS, LSH, and RASearch API; these classes now take the query sets in the Search() method, instead of in the constructor.
  • Use OpenMP, if available. For now OpenMP support is only available in the DET training code.
  • Add support for predicting new test point values to LARS and the command-line 'lars' program.
  • Add serialization support for Perceptron and LogisticRegression.
  • Refactor SoftmaxRegression to predict into an arma::Row object, and add a softmax_regression program.
  • Refactor LSH to allow loading and saving of models.
  • ToString() is removed entirely (#487).
  • Add --input_model_file and --output_model_file options to appropriate machine learning algorithms.
  • Rename all executables to start with an "mlpack" prefix (#229).

See also for more information.

January 11, 2016, 17:24:35
  • Switch to 3-clause BSD license.
January 7, 2015, 19:23:51
  • Proper handling of dimension calculation in PCA.
  • Load parameter vectors properly for LinearRegression models.
  • Linker fixes for AugLagrangian specializations under Visual Studio.
  • Add support for observation weights to LinearRegression.
  • MahalanobisDistance<> now takes root of the distance by default and therefore satisfies the triangle inequality (TakeRoot now defaults to true).
  • Better handling of optional Armadillo HDF5 dependency.
  • Fixes for numerous intermittent test failures.
  • math::RandomSeed() now sets the seed for recent (>= 3.930) Armadillo versions.
  • Handle Newton method convergence better for SparseCoding::OptimizeDictionary() and make maximum iterations a parameter.
  • Known bug: CosineTree construction may fail in some cases on i386 systems (376).
December 11, 2014, 18:20:35
  • Bugfix for NeighborSearch regression which caused very slow allknn/allkfn. Speeds are nwo restored to approximately 1.0.8 speeds, with significant improvement for the cover tree (#365).
  • Detect dependencies correctly when ARMA_USE_WRAPPER is not defined (i.e. does not exist).
  • Bugfix for compilation under Visual Studio (#366).
August 29, 2014, 21:26:18
  • GMM initialization is now safer and provides a working GMM when constructed with only the dimensionality and number of Gaussians (#314).
  • Check for division by 0 in Forward-Backward Algorithm in HMMs (#314).
  • Fix MaxVarianceNewCluster (used when re-initializing clusters for k-means) (#314).
  • Fixed implementation of Viterbi algorithm in HMM::Predict() (#316).
  • Significant speedups for dual-tree algorithms using the cover tree (#243, #329) including a faster implementation of FastMKS.
  • Fix for LRSDP optimizer so that it compiles and can be used (#325).
  • CF (collaborative filtering) now expects users and items to be zero-indexed, not one-indexed (#324).
  • CF::GetRecommendations() API change: now requires the number of recommendations as the first parameter. The number of users in the local neighborhood should be specified with CF::NumUsersForSimilarity().
  • Removed incorrect PeriodicHRectBound (#30).
  • Refactor LRSDP into LRSDP class and standalone function to be optimized (#318).
  • Fix for centering in kernel PCA (#355).
  • Added simulated annealing (SA) optimizer, contributed by Zhihao Lou.
  • HMMs now support initial state probabilities; these can be set in the constructor, trained, or set manually with HMM::Initial() (#315).
  • Added Nyström method for kernel matrix approximation by Marcus Edel.
  • Kernel PCA now supports using Nyström method for approximation.
  • Ball trees now work with dual-tree algorithms, via the BallBound<> bound structure (#320); fixed by Yash Vadalia.
  • The NMF class is now AMF<>, and supports far more types of factorizations, by Sumedh Ghaisas.
  • A QUIC-SVD implementation has returned, written by Siddharth Agrawal and based on older code from Mudit Gupta.
  • Added perceptron and decision stump by Udit Saxena (these are weak learners for an eventual AdaBoost class).
  • Sparse autoencoder added by Siddharth Agrawal.
July 28, 2014, 20:52:10
  • Memory leak in NeighborSearch index-mapping code fixed.
  • GMMs can be trained using the existing model as a starting point by specifying an additional boolean parameter to GMM::Estimate().
  • Logistic regression implementation added in methods/logistic_regression.
  • Version information is now obtainable via mlpack::util::GetVersion() or the _MLPACKVERSION_MAJOR, _MLPACKVERSION_MINOR, and _MLPACKVERSION_PATCH macros.
  • Fix typos in allkfn and allkrann output.
January 7, 2014, 05:47:22
  • Cover tree support for range_search, rank-approximate nearest neighbors, minimum spanning tree calculation, and FastMKS.
  • Dual-tree FastMKS implementation added and tests.
  • Added collaborative filtering package that can provide recommendations when given users and items.
  • Fix for correctness of Kernel PCA.
  • Speedups for PCA and Kernel PCA.
  • Fix for correctness of Neighborhood Components Analysis (NCA).
  • Minor speedups for dual-tree algorithms.
  • Fix for Naive Bayes Classifier (nbc).
  • Added a ridge regression option to LinearRegression (linear_regression).
  • Gaussian Mixture Models (gmm::GMM<>) now support arbitrary covariance matrix constraints.
  • MVU removed because it is known to not work.
  • Minor updates and fixes for kernels (in mlpack::kernel).
October 4, 2013, 22:24:48

Minor bugfix so that FastMKS gets built.

June 13, 2013, 21:26:10

Speedups of cover tree traversers; addition of rank-approximate nearest neighbor (RANN); addition of fast exact max-kernel search (FastMKS); fix for EM covariance estimation; more parameters for GMM estimation; force GMM and GaussianDistribution covariance matrices to be positive definite during training; add a tolerance parameter to the Baum-Welch algorithm for HMM training; fix for compilation with clang; fix for k-furthest neighbor search.

May 2, 2013, 07:24:32

Force minimum Armadillo version of 2.4.2; add locality-sensitive hashing (LSH); handle size_t support correctly with Armadillo 3.6.2; better tests for SGD and NCA; better output of types to streams; some style fixes.

February 8, 2013, 22:32:43

Armadillo 3.4.0 includes sparse matrix support internally; MLPACK's internal sparse matrix support has thus been removed.

September 17, 2012, 01:27:19

Added density estimation trees, nonnegative matrix factorization, an experimental cover tree implementation, and several bugfixes. See for a full listing of tickets closed.

August 15, 2012, 20:47:13

Added local coordinate coding, sparse coding, kernel PCA, and several bugfixes.

March 20, 2012, 20:59:53

Yet another announcement on

December 17, 2011, 10:37:05

Initial Announcement on

November 20, 2009, 04:01:36

Initial Announcement on

October 7, 2008, 07:12:37


Eileen (on February 13, 2009, 12:13:23)

having this problem when running fl-build-all

/bin/sh: g++4: not found make: * [$FASTLIBPATH/bin/i686_Linux_fast_gcc4_-DDISABLE_DISK_MATRIX/obj/mlpack_allnn_main.o] Error 127

and a whole lot of similar error

Am i missing something?

fastlab (on February 14, 2009, 03:55:05)

You need to install gcc 4. Which platform are you running on?

Paul Rodriguez (on December 21, 2010, 21:38:24)


I've set up the ccmake configuration options as appropriate but now I'm having trouble with the make command described below,

thanks, Paul Rodriguez

Using a santos linux, on an intel 64 bit processor, when I execute "make install" I get the following error regarding pthread_atfork:

-- A library with BLAS API found. -- A library with BLAS API found. -- A library with LAPACK API found. -- Configuring done -- Generating done -- Build files have been written to: /users/sdsc/prodriguez/mlpack-0.2/fastlib/build [ 2%] Built target template_types [ 5%] Built target template_types_detect [ 17%] Built target base [ 20%] Built target col [ 23%] Built target file [ 30%] Built target fx [ 33%] Built target la [ 35%] Built target data [ 35%] Built target tree [ 43%] Built target math [ 46%] Built target par [ 87%] Built target fastlib [ 89%] Built target otrav_test [ 92%] Built target col_test [ 94%] Building CXX object fastlib/data/CMakeFiles/dataset_test.dir/ Linking CXX executable dataset_test /rmount/usr_apps/compilers/intel/Compiler/11.1/038/lib/intel64/ undefined reference to `pthread_atfork' collect2: ld returned 1 exit status make[2]: [fastlib/data/dataset_test] Error 1 make[1]: [fastlib/data/CMakeFiles/dataset_test.dir/all] Error 2 make: * [all] Error 2

Andreas Mueller (on March 20, 2012, 13:29:07)

Two comments: 1) I have not found a way to contact the project on the project website. Having to come to mloss and logging in to contact the developers seems a bit weird.

2) mlpack does not seems to build with armadilla in a non-standard location. After trying to feed cmake the correct pathes for a while I gave up and installed globally. In particular, setting the paths in the CMake configuration doesn't help much. Would be cool if you could fix that.

Cheers, Andy

Ryan Curtin (on March 20, 2012, 20:22:49)

Hello Andy,

I've clarified a bit to note that the Trac site is where bugs can be filed.

As for finding Armadillo, I have not had a problem doing the following (in this instance, I've got Armadillo 2.99.1 built in /home/ryan/src/armadillo-2.99.1/)

build$ cmake -D ARMADILLO_INCLUDE_DIR=/home/ryan/src/armadillo-2.99.1/build/ -D ARMADILLO_LIBRARY=/home/ryan/src/armadillo-2.99.1/ ../

Did those two variables (ARMADILLO_INCLUDE_DIR and ARMADILLO_LIBRARY) not work for you? If you're still having problems (or have other problems) feel free to file a ticket at

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