NAME

       mlpack_approx_kfn - approximate furthest neighbor search

SYNOPSIS

        mlpack_approx_kfn [-a string] [-e bool] [-x string] [-m unknown] [-k int] [-p int] [-t int] [-q string] [-r string] [-V bool] [-d string] [-n string] [-M unknown] [-h -v]

DESCRIPTION

       This program implements two strategies for furthest neighbor search. These strategies are:

              •  The 'qdafn' algorithm from "Approximate Furthest Neighbor in High Dimensions" by
                 R. Pagh, F. Silvestri, J. Sivertsen, and M.  Skala,  in  Similarity  Search  and
                 Applications 2015 (SISAP).

              •  The  'DrusillaSelect'  algorithm  from "Fast approximate furthest neighbors with
                 data-dependent candidate  selection",  by  R.R.  Curtin  and  A.B.  Gardner,  in
                 Similarity Search and Applications 2016 (SISAP).

       These two strategies give approximate results for the furthest neighbor search problem and
       can be used as fast replacements for other furthest  neighbor  techniques  such  as  those
       found  in  the  mlpack_kfn  program.  Note that typically, the 'ds' algorithm requires far
       fewer tables and projections than the 'qdafn' algorithm.

       Specify a reference set (set to search in) with '--reference_file (-r)', specify  a  query
       set  with  '--query_file  (-q)', and specify algorithm parameters with '--num_tables (-t)'
       and '--num_projections (-p)' (or don't and defaults will be used).  The  algorithm  to  be
       used  (either  'ds'---the  default---or ’qdafn') may be specified with '--algorithm (-a)'.
       Also specify the number of neighbors to search for with '--k (-k)'.

       Note that for 'qdafn' in lower dimensions, '--num_projections (-p)' may need to be set  to
       a high value in order to return results for each query point.

       If  no  query  set  is  specified,  the  reference set will be used as the query set.  The
       '--output_model_file (-M)' output parameter may be used to store the built model,  and  an
       input   model   may   be   loaded   instead   of  specifying  a  reference  set  with  the
       '--input_model_file (-m)' option.

       Results for  each  query  point  can  be  stored  with  the  '--neighbors_file  (-n)'  and
       '--distances_file  (-d)'  output parameters. Each row of these output matrices holds the k
       distances or neighbor indices for each query point.

       For example, to find the 5 approximate furthest neighbors with ’reference_set.csv' as  the
       reference  set  and  'query_set.csv'  as  the  query set using DrusillaSelect, storing the
       furthest neighbor indices to  'neighbors.csv'  and  the  furthest  neighbor  distances  to
       'distances.csv', one could call

       $  mlpack_approx_kfn  --query_file  query_set.csv --reference_file reference_set.csv --k 5
       --algorithm ds --neighbors_file neighbors.csv --distances_file distances.csv

       and to perform approximate all-furthest-neighbors search with k=1 on  the  set  ’data.csv'
       storing only the furthest neighbor distances to 'distances.csv', one could call

       $    mlpack_approx_kfn   --reference_file   reference_set.csv   --k   1   --distances_file
       distances.csv

       A trained model can be re-used. If a model has been previously saved to ’model.bin',  then
       we may find 3 approximate furthest neighbors on a query set ’new_query_set.csv' using that
       model and store the furthest neighbor indices into 'neighbors.csv' by calling

       $ mlpack_approx_kfn --input_model_file  model.bin  --query_file  new_query_set.csv  --k  3
       --neighbors_file neighbors.csv

OPTIONAL INPUT OPTIONS

       --algorithm (-a) [string]
              Algorithm to use: 'ds' or 'qdafn'. Default value 'ds'.

       --calculate_error (-e) [bool]
              If set, calculate the average distance error for the first furthest neighbor only.

       --exact_distances_file (-x) [string]
              Matrix  containing exact distances to furthest neighbors; this can be used to avoid
              explicit calculation when --calculate_error is set.

       --help (-h) [bool]
              Default help info.

       --info [string]
              Print help on a specific option. Default value ''.

       --input_model_file (-m) [unknown]
              File containing input model.

       --k (-k) [int]
              Number of furthest neighbors to search for.  Default  value  0.   --num_projections
              (-p) [int] Number of projections to use in each hash table. Default value 5.

       --num_tables (-t) [int]
              Number of hash tables to use. Default value 5.

       --query_file (-q) [string]
              Matrix containing query points.

       --reference_file (-r) [string]
              Matrix containing the reference dataset.

       --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

       --distances_file (-d) [string]
              Matrix to save furthest neighbor distances to.

       --neighbors_file (-n) [string]
              Matrix to save neighbor indices to.

       --output_model_file (-M) [unknown]
              File to save output model to.

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.