Provided by: mlpack-bin_4.1.0-1ubuntu1_amd64 
NAME
mlpack_lmnn - large margin nearest neighbors (lmnn)
SYNOPSIS
mlpack_lmnn -i unknown [-b int] [-C bool] [-d unknown] [-k int] [-l unknown] [-L bool] [-n int] [-N bool] [-O string] [-p int] [-P bool] [-R int] [-A int] [-r double] [-s int] [-a double] [-t double] [-V bool] [-c unknown] [-o unknown] [-D unknown] [-h -v]
DESCRIPTION
This program implements Large Margin Nearest Neighbors, a distance learning technique. The
method seeks to improve k-nearest-neighbor classification on a dataset. The method
employes the strategy of reducing distance between similar labeled data points (a.k.a
target neighbors) and increasing distance between differently labeled points (a.k.a
impostors) using standard optimization techniques over the gradient of the distance
between data points.
To work, this algorithm needs labeled data. It can be given as the last row of the input
dataset (specified with '--input_file (-i)'), or alternatively as a separate matrix
(specified with '--labels_file (-l)'). Additionally, a starting point for optimization
(specified with '--distance_file (-d)'can be given, having (r x d) dimensionality. Here r
should satisfy 1 <= r <= d, Consequently a Low-Rank matrix will be optimized.
Alternatively, Low-Rank distance can be learned by specifying the '--rank (-A)'parameter
(A Low-Rank matrix with uniformly distributed values will be used as initial learning
point).
The program also requires number of targets neighbors to work with ( specified with '--k
(-k)'), A regularization parameter can also be passed, It acts as a trade of between the
pulling and pushing terms (specified with ’--regularization (-r)'), In addition, this
implementation of LMNN includes a parameter to decide the interval after which impostors
must be re-calculated (specified with '--range (-R)').
Output can either be the learned distance matrix (specified with ’--output_file (-o)'), or
the transformed dataset (specified with ’--transformed_data_file (-D)'), or both.
Additionally mean-centered dataset (specified with '--centered_data_file (-c)') can be
accessed given mean-centering (specified with '--center (-C)') is performed on the
dataset. Accuracy on initial dataset and final transformed dataset can be printed by
specifying the '--print_accuracy (-P)'parameter.
This implementation of LMNN uses AdaGrad, BigBatch_SGD, stochastic gradient descent, mini-
batch stochastic gradient descent, or the L_BFGS optimizer.
AdaGrad, specified by the value 'adagrad' for the parameter '--optimizer (-O)', uses
maximum of past squared gradients. It primarily on six parameters: the step size
(specified with '--step_size (-a)'), the batch size (specified with '--batch_size (-b)'),
the maximum number of passes (specified with ’--passes (-p)'). Inaddition, a normalized
starting point can be used by specifying the '--normalize (-N)' parameter.
BigBatch_SGD, specified by the value 'bbsgd' for the parameter '--optimizer (-O)', depends
primarily on four parameters: the step size (specified with ’--step_size (-a)'), the batch
size (specified with '--batch_size (-b)'), the maximum number of passes (specified with
'--passes (-p)'). In addition, a normalized starting point can be used by specifying the
'--normalize (-N)' parameter.
Stochastic gradient descent, specified by the value 'sgd' for the parameter ’--optimizer
(-O)', depends primarily on three parameters: the step size (specified with '--step_size
(-a)'), the batch size (specified with ’--batch_size (-b)'), and the maximum number of
passes (specified with ’--passes (-p)'). In addition, a normalized starting point can be
used by specifying the '--normalize (-N)' parameter. Furthermore, mean-centering can be
performed on the dataset by specifying the '--center (-C)'parameter.
The L-BFGS optimizer, specified by the value 'lbfgs' for the parameter ’--optimizer (-O)',
uses a back-tracking line search algorithm to minimize a function. The following
parameters are used by L-BFGS: '--max_iterations (-n)', '--tolerance (-t)'(the
optimization is terminated when the gradient norm is below this value). For more details
on the L-BFGS optimizer, consult either the mlpack L-BFGS documentation (in lbfgs.hpp) or
the vast set of published literature on L-BFGS. In addition, a normalized starting point
can be used by specifying the '--normalize (-N)' parameter.
By default, the AMSGrad optimizer is used.
Example - Let's say we want to learn distance on iris dataset with number of targets as 3
using BigBatch_SGD optimizer. A simple call for the same will look like:
$ mlpack_lmnn --input_file iris.csv --labels_file iris_labels.csv --k 3 --optimizer bbsgd
--output_file output.csv
An another program call making use of range & regularization parameter with dataset having
labels as last column can be made as:
$ mlpack_lmnn --input_file letter_recognition.csv --k 5 --range 10 --regularization 0.4
--output_file output.csv
REQUIRED INPUT OPTIONS
--input_file (-i) [unknown]
Input dataset to run LMNN on.
OPTIONAL INPUT OPTIONS
--batch_size (-b) [int]
Batch size for mini-batch SGD. Default value 50.
--center (-C) [bool]
Perform mean-centering on the dataset. It is useful when the centroid of the data
is far from the origin.
--distance_file (-d) [unknown]
Initial distance matrix to be used as starting point
--help (-h) [bool]
Default help info.
--info [string]
Print help on a specific option. Default value ''.
--k (-k) [int]
Number of target neighbors to use for each datapoint. Default value 1.
--labels_file (-l) [unknown] Labels for input dataset.
--linear_scan (-L) [bool]
Don't shuffle the order in which data points are visited for SGD or mini-batch SGD.
--max_iterations (-n) [int]
Maximum number of iterations for L-BFGS (0 indicates no limit). Default value
100000.
--normalize (-N) [bool]
Use a normalized starting point for optimization. Itis useful for when points are
far apart, or when SGD is returning NaN.
--optimizer (-O) [string]
Optimizer to use; 'amsgrad', 'bbsgd', 'sgd', or 'lbfgs'. Default value 'amsgrad'.
--passes (-p) [int]
Maximum number of full passes over dataset for AMSGrad, BB_SGD and SGD. Default
value 50. --print_accuracy (-P) [bool] Print accuracies on initial and transformed
dataset
--range (-R) [int]
Number of iterations after which impostors needs to be recalculated Default value
1.
--rank (-A) [int]
Rank of distance matrix to be optimized. Default value 0.
--regularization (-r) [double]
Regularization for LMNN objective function Default value 0.5.
--seed (-s) [int]
Random seed. If 0, 'std::time(NULL)' is used. Default value 0.
--step_size (-a) [double]
Step size for AMSGrad, BB_SGD and SGD (alpha). Default value 0.01.
--tolerance (-t) [double]
Maximum tolerance for termination of AMSGrad, BB_SGD, SGD or L-BFGS. Default value
1e-07.
--verbose (-v) [bool]
Display informational messages and the full list of parameters and timers at the
end of execution.
--version (-V) [bool]
Display the version of mlpack.
OPTIONAL OUTPUT OPTIONS
--centered_data_file (-c) [unknown]
Output matrix for mean-centered dataset. --output_file (-o) [unknown] Output
matrix for learned distance matrix.
--transformed_data_file (-D) [unknown]
Output matrix for transformed dataset.
ADDITIONAL INFORMATION
For further information, including relevant papers, citations, and theory, consult the
documentation found at http://www.mlpack.org or included with your distribution of mlpack.