readme

svm的实现源码

Two things are provided in this directory: an automatic model selection
tool and a python binding for libsvm.

		Part I: Model Selection Tools

Introduction
===============

grid.py is a model selection tool for C-SVM classification using rbf
(radial basis function) kernel. It uses cross validation (CV) technique
to estimate the accuracy of each parameter combination in the specified 
range and helps you to decide the best parameters for your problem.

grid.py directly executes libsvm binaries (so no python binding is needed)
for cross validation and then draw contour of CV accuracy using gnuplot.
You must have libsvm and gnuplot installed before using it. The package 
gnuplot is available at http://www.gnuplot.info/

Usage: grid.py [-log2c begin,end,step] [-log2g begin,end,step] [-v fold] 
       [-svmtrain pathname] [-gnuplot pathname] [-out pathname] [-png pathname]  
       [additional parameters for svm-train] dataset

The program conducts v-fold cross valiation using parameter C (and gamma) 
= 2^begin, 2^(begin+step), ..., 2^end. 

You can specify where the libsvm executable and gnuplot are using the
-svmtrain and -gnuplot parameters.

For windows users, if you are using gnuplot 3.7.1, please upgrade to version
3.7.3. The pgnuplot.exe in version 3.7.1 has a bug.

Example
=======

> python grid.py -log2c -5,5,1 -log2g -4,0,1 -v 5 -m 300 heart_scale

(Windows users might also use "start grid.py" instead of "python grid.py")

Output: two files
dataset.png: the contour plot of the CV accuracy (generated by gnuplot)
dataset.out: the log of accuracy at each (C,gamma)

Parallel grid search (experimental)
===================================

You can conduct a parallel grid search by dispatching jobs to a cluster of 
computers which share the same file system. First, you add machine names 
in grid.py:

telnet_workers = ["linux1", "linux5", "linux5"]

The same machine (e.g., linux5 here) can be listed more than once if
it has multiple CPUs or has more RAM. If the local machine is the
best, you can also enlarge the nr_local_worker. For example:

nr_local_worker = 2

Example:

> python grid.py heart_scale
Password: ********

login ok linux1
login ok linux5
login ok linux5
.
.
.

The password is the one used for entering your system. If -log2c, -log2g, or
-v is not specified, defaule values are used. 

If your system uses ssh instead of telnet, you should setup ssh first so that
the authentication works without asking a password, and list the computer names
in ssh_workers.