libsvm websitelibsvm - A simple, easy-to-use, efficient library for Support Vector Machines. [BSD-3-Clause] website

Libsvm is a simple, easy-to-use, and efficient software for SVM
classification and regression. It solves C-SVM classification, nu-SVM
classification, one-class-SVM, epsilon-SVM regression, and nu-SVM
regression. It also provides an automatic model selection tool for
C-SVM classification. This document explains the use of libsvm.

Libsvm is available at
Please read the COPYRIGHT file before using libsvm.

Table of Contents

- Quick Start
- Installation and Data Format
- `svm-train' Usage
- `svm-predict' Usage
- `svm-scale' Usage
- Tips on Practical Use
- Examples
- Precomputed Kernels
- Library Usage
- Java Version
- Building Windows Binaries
- Additional Tools: Sub-sampling, Parameter Selection, Format checking, etc.
- Python Interface
- Additional Information

Quick Start

If you are new to SVM and if the data is not large, please go to
`tools' directory and use after installation. It does
everything automatic -- from data scaling to parameter selection.

Usage: training_file [testing_file]

More information about parameter selection can be found in

Installation and Data Format

On Unix systems, type `make' to build the `svm-train', `svm-predict',
and `svm-scale' programs. Run them without arguments to show the
usages of them.

On other systems, consult `Makefile' to build them (e.g., see
'Building Windows binaries' in this file) or use the pre-built
binaries (Windows binaries are in the directory `windows').

The format of training and testing data files is:

<label> <index1>:<value1> <index2>:<value2> ...

Each line contains an instance and is ended by a '\n' character. For
<label> in the training set, we have the following cases.

* classification: <label> is an integer indicating the class label
  (multi-class is supported).

* For regression, <label> is the target value which can be any real

* For one-class SVM, <label> is not used and can be any number.

In the test set, <label> is used only to calculate accuracy or
errors. If it's unknown, any number is fine. For one-class SVM, if
non-outliers/outliers are known, their labels in the test file must be
+1/-1 for evaluation.

The pair <index>:<value> gives a feature (attribute) value: <index> is
an integer starting from 1 and <value> is a real number. The only
exception is the precomputed kernel, where <index> starts from 0; see
the section of precomputed kernels. Indices must be in ASCENDING

A sample classification data included in this package is
`heart_scale'. To check if your data is in a correct form, use
`tools/' (details in `tools/README').

Type `svm-train heart_scale', and the program will read the training
data and output the model file `heart_scale.model'. If you have a test
set called heart_scale.t, then type `svm-predict heart_scale.t
heart_scale.model output' to see the prediction accuracy. The `output'
file contains the predicted class labels.

For classification, if training data are in only one class (i.e., all
labels are the same), then `svm-train' issues a warning message:
`Warning: training data in only one class. See README for details,'
which means the training data is very unbalanced. The label in the
training data is directly returned when testing.

There are some other useful programs in this package.


	This is a tool for scaling input data file.


	This is a simple graphical interface which shows how SVM
	separate data in a plane. You can click in the window to
	draw data points. Use "change" button to choose class
	1, 2 or 3 (i.e., up to three classes are supported), "load"
	button to load data from a file, "save" button to save data to
	a file, "run" button to obtain an SVM model, and "clear"
	button to clear the window.

	You can enter options in the bottom of the window, the syntax of
	options is the same as `svm-train'.

	Note that "load" and "save" consider dense data format both in
	classification and the regression cases. For classification,
	each data point has one label (the color) that must be 1, 2,
	or 3 and two attributes (x-axis and y-axis values) in
	[0,1). For regression, each data point has one target value
	(y-axis) and one attribute (x-axis values) in [0, 1).

	Type `make' in respective directories to build them.

	You need Qt library to build the Qt version.
	(available from

	You need GTK+ library to build the GTK version.
	(available from

	The pre-built Windows binaries are in the `windows'
	directory. We use Visual C++ on a 64-bit machine.

`svm-train' Usage

Usage: svm-train [options] training_set_file [model_file]
-s svm_type : set type of SVM (default 0)
	0 -- C-SVC		(multi-class classification)
	1 -- nu-SVC		(multi-class classification)
	2 -- one-class SVM
	3 -- epsilon-SVR	(regression)
	4 -- nu-SVR		(regression)
-t kernel_type : set type of kernel function (default 2)
	0 -- linear: u'*v
	1 -- polynomial: (gamma*u'*v + coef0)^degree
	2 -- radial basis function: exp(-gamma*|u-v|^2)
	3 -- sigmoid: tanh(gamma*u'*v + coef0)
	4 -- precomputed kernel (kernel values in training_set_file)
-d degree : set degree in kernel function (default 3)
-g gamma : set gamma in kernel function (default 1/num_features)
-r coef0 : set coef0 in kernel function (default 0)
-c cost : set the parameter C of C-SVC, epsilon-SVR, and nu-SVR (default 1)
-n nu : set the parameter nu of nu-SVC, one-class SVM, and nu-SVR (default 0.5)
-p epsilon : set the epsilon in loss function of epsilon-SVR (default 0.1)
-m cachesize : set cache memory size in MB (default 100)
-e epsilon : set tolerance of termination criterion (default 0.001)
-h shrinking : whether to use the shrinking heuristics, 0 or 1 (default 1)
-b probability_estimates : whether to train a SVC or SVR model for probability estimates, 0 or 1 (default 0)
-wi weight : set the parameter C of class i to weight*C, for C-SVC (default 1)
-v n: n-fold cross validation mode
-q : quiet mode (no outputs)

option -v randomly splits the data into n parts and calculates cross
validation accuracy/mean squared error on them.

See libsvm FAQ for the meaning of outputs.

`svm-predict' Usage

Usage: svm-predict [options] test_file model_file output_file
-b probability_estimates: whether to predict probability estimates, 0 or 1 (default 0); for one-class SVM only 0 is supported

model_file is the model file generated by svm-train.
test_file is the test data you want to predict.
svm-predict will produce output in the output_file.

`svm-scale' Usage

Usage: svm-scale [options] data_filename
-l lower : x scaling lower limit (default -1)
-u upper : x scaling upper limit (default +1)
-y y_lower y_upper : y scaling limits (default: no y scaling)
-s save_filename : save scaling parameters to save_filename
-r restore_filename : restore scaling parameters from restore_filename

See 'Examples' in this file for examples.

Tips on Practical Use

* Scale your data. For example, scale each attribute to [0,1] or [-1,+1].
* For C-SVC, consider using the model selection tool in the tools directory.
* nu in nu-SVC/one-class-SVM/nu-SVR approximates the fraction of training
  errors and support vectors.
* If data for classification are unbalanced (e.g. many positive and
  few negative), try different penalty parameters C by -wi (see
  examples below).
* Specify larger cache size (i.e., larger -m) for huge problems.


> svm-scale -l -1 -u 1 -s range train > train.scale
> svm-scale -r range test > test.scale

Scale each feature of the training data to be in [-1,1]. Scaling
factors are stored in the file range and then used for scaling the
test data.

> svm-train -s 0 -c 5 -t 2 -g 0.5 -e 0.1 data_file

Train a classifier with RBF kernel exp(-0.5|u-v|^2), C=10, and
stopping tolerance 0.1.

> svm-train -s 3 -p 0.1 -t 0 data_file

Solve SVM regression with linear kernel u'v and epsilon=0.1
in the loss function.

> svm-train -c 10 -w1 1 -w-2 5 -w4 2 data_file

Train a classifier with penalty 10 = 1 * 10 for class 1, penalty 50 =
5 * 10 for class -2, and penalty 20 = 2 * 10 for class 4.

> svm-train -s 0 -c 100 -g 0.1 -v 5 data_file

Do five-fold cross validation for the classifier using
the parameters C = 100 and gamma = 0.1

> svm-train -s 0 -b 1 data_file
> svm-predict -b 1 test_file data_file.model output_file

Obtain a model with probability information and predict test data with
probability estimates

Precomputed Kernels

Users may precompute kernel values and input them as training and
testing files.  Then libsvm does not need the original
training/testing sets.

Assume there are L training instances x1, ..., xL and.
Let K(x, y) be the kernel
value of two instances x and y. The input formats

New training instance for xi:

<label> 0:i 1:K(xi,x1) ... L:K(xi,xL)

New testing instance for any x:

<label> 0:? 1:K(x,x1) ... L:K(x,xL)

That is, in the training file the first column must be the "ID" of
xi. In testing, ? can be any value.

All kernel values including ZEROs must be explicitly provided.  Any
permutation or random subsets of the training/testing files are also
valid (see examples below).

Note: the format is slightly different from the precomputed kernel
package released in libsvmtools earlier.


	Assume the original training data has three four-feature
	instances and testing data has one instance:

	15  1:1 2:1 3:1 4:1
	45      2:3     4:3
	25          3:1

	15  1:1     3:1

	If the linear kernel is used, we have the following new
	training/testing sets:

	15  0:1 1:4 2:6  3:1
	45  0:2 1:6 2:18 3:0
	25  0:3 1:1 2:0  3:1

	15  0:? 1:2 2:0  3:1

	? can be any value.

	Any subset of the above training file is also valid. For example,

	25  0:3 1:1 2:0  3:1
	45  0:2 1:6 2:18 3:0

	implies that the kernel matrix is

		[K(2,2) K(2,3)] = [18 0]
		[K(3,2) K(3,3)] = [0  1]

Library Usage

These functions and structures are declared in the header file
`svm.h'.  You need to #include "svm.h" in your C/C++ source files and
link your program with `svm.cpp'. You can see `svm-train.c' and
`svm-predict.c' for examples showing how to use them. We define
LIBSVM_VERSION and declare `extern int libsvm_version;' in svm.h, so
you can check the version number.

Before you classify test data, you need to construct an SVM model
(`svm_model') using training data. A model can also be saved in
a file for later use. Once an SVM model is available, you can use it
to classify new data.

- Function: struct svm_model *svm_train(const struct svm_problem *prob,
					const struct svm_parameter *param);

    This function constructs and returns an SVM model according to
    the given training data and parameters.

    struct svm_problem describes the problem:

	struct svm_problem
		int l;
		double *y;
		struct svm_node **x;

    where `l' is the number of training data, and `y' is an array containing
    their target values. (integers in classification, real numbers in
    regression) `x' is an array of pointers, each of which points to a sparse
    representation (array of svm_node) of one training vector.

    For example, if we have the following training data:

    LABEL    ATTR1    ATTR2    ATTR3    ATTR4    ATTR5
    -----    -----    -----    -----    -----    -----
      1        0        0.1      0.2      0        0
      2        0        0.1      0.3     -1.2      0
      1        0.4      0        0        0        0
      2        0        0.1      0        1.4      0.5
      3       -0.1     -0.2      0.1      1.1      0.1

    then the components of svm_problem are:

    l = 5

    y -> 1 2 1 2 3

    x -> [ ] -> (2,0.1) (3,0.2) (-1,?)
         [ ] -> (2,0.1) (3,0.3) (4,-1.2) (-1,?)
         [ ] -> (1,0.4) (-1,?)
         [ ] -> (2,0.1) (4,1.4) (5,0.5) (-1,?)
         [ ] -> (1,-0.1) (2,-0.2) (3,0.1) (4,1.1) (5,0.1) (-1,?)

    where (index,value) is stored in the structure `svm_node':

	struct svm_node
		int index;
		double value;

    index = -1 indicates the end of one vector. Note that indices must
    be in ASCENDING order.

    struct svm_parameter describes the parameters of an SVM model:

	struct svm_parameter
		int svm_type;
		int kernel_type;
		int degree;	/* for poly */
		double gamma;	/* for poly/rbf/sigmoid */
		double coef0;	/* for poly/sigmoid */

		/* these are for training only */
		double cache_size; /* in MB */
		double eps;	/* stopping criteria */
		double C;	/* for C_SVC, EPSILON_SVR, and NU_SVR */
		int nr_weight;		/* for C_SVC */
		int *weight_label;	/* for C_SVC */
		double* weight;		/* for C_SVC */
		double nu;	/* for NU_SVC, ONE_CLASS, and NU_SVR */
		double p;	/* for EPSILON_SVR */
		int shrinking;	/* use the shrinking heuristics */
		int probability; /* do probability estimates */

    svm_type can be one of C_SVC, NU_SVC, ONE_CLASS, EPSILON_SVR, NU_SVR.

    C_SVC:		C-SVM classification
    NU_SVC:		nu-SVM classification
    ONE_CLASS:		one-class-SVM
    EPSILON_SVR:	epsilon-SVM regression
    NU_SVR:		nu-SVM regression

    kernel_type can be one of LINEAR, POLY, RBF, SIGMOID.

    LINEAR:	u'*v
    POLY:	(gamma*u'*v + coef0)^degree
    RBF:	exp(-gamma*|u-v|^2)
    SIGMOID:	tanh(gamma*u'*v + coef0)
    PRECOMPUTED: kernel values in training_set_file

    cache_size is the size of the kernel cache, specified in megabytes.
    C is the cost of constraints violation.
    eps is the stopping criterion. (we usually use 0.00001 in nu-SVC,
    0.001 in others). nu is the parameter in nu-SVM, nu-SVR, and
    one-class-SVM. p is the epsilon in epsilon-insensitive loss function
    of epsilon-SVM regression. shrinking = 1 means shrinking is conducted;
    = 0 otherwise. probability = 1 means model with probability
    information is obtained; = 0 otherwise.

    nr_weight, weight_label, and weight are used to change the penalty
    for some classes (If the weight for a class is not changed, it is
    set to 1). This is useful for training classifier using unbalanced
    input data or with asymmetric misclassification cost.

    nr_weight is the number of elements in the array weight_label and
    weight. Each weight[i] corresponds to weight_label[i], meaning that
    the penalty of class weight_label[i] is scaled by a factor of weight[i].

    If you do not want to change penalty for any of the classes,
    just set nr_weight to 0.

    *NOTE* Because svm_model contains pointers to svm_problem, you can
    not free the memory used by svm_problem if you are still using the
    svm_model produced by svm_train().

    *NOTE* To avoid wrong parameters, svm_check_parameter() should be
    called before svm_train().

    struct svm_model stores the model obtained from the training procedure.
    It is not recommended to directly access entries in this structure.
    Programmers should use the interface functions to get the values.

	struct svm_model
		struct svm_parameter param;	/* parameter */
		int nr_class;		/* number of classes, = 2 in regression/one class svm */
		int l;			/* total #SV */
		struct svm_node **SV;		/* SVs (SV[l]) */
		double **sv_coef;	/* coefficients for SVs in decision functions (sv_coef[k-1][l]) */
		double *rho;		/* constants in decision functions (rho[k*(k-1)/2]) */
		double *probA;		/* pairwise probability information */
		double *probB;
		int *sv_indices;        /* sv_indices[0,...,nSV-1] are values in [1,...,num_traning_data] to indicate SVs in the training set */

		/* for classification only */

		int *label;		/* label of each class (label[k]) */
		int *nSV;		/* number of SVs for each class (nSV[k]) */
					/* nSV[0] + nSV[1] + ... + nSV[k-1] = l */
		/* XXX */
		int free_sv;		/* 1 if svm_model is created by svm_load_model*/
					/* 0 if svm_model is created by svm_train */

    param describes the parameters used to obtain the model.

    nr_class is the number of classes. It is 2 for regression and one-class SVM.

    l is the number of support vectors. SV and sv_coef are support
    vectors and the corresponding coefficients, respectively. Assume there are
    k classes. For data in class j, the corresponding sv_coef includes (k-1) y*alpha vectors,
    where alpha's are solutions of the following two class problems:
    1 vs j, 2 vs j, ..., j-1 vs j, j vs j+1, j vs j+2, ..., j vs k
    and y=1 for the first j-1 vectors, while y=-1 for the remaining k-j
    vectors. For example, if there are 4 classes, sv_coef and SV are like:

        |1|1|1|                    |
        |v|v|v|  SVs from class 1  |
        |2|3|4|                    |
        |1|2|2|                    |
        |v|v|v|  SVs from class 2  |
        |2|3|4|                    |
        |1|2|3|                    |
        |v|v|v|  SVs from class 3  |
        |3|3|4|                    |
        |1|2|3|                    |
        |v|v|v|  SVs from class 4  |
        |4|4|4|                    |

    See svm_train() for an example of assigning values to sv_coef.

    rho is the bias term (-b). probA and probB are parameters used in
    probability outputs. If there are k classes, there are k*(k-1)/2
    binary problems as well as rho, probA, and probB values. They are
    aligned in the order of binary problems:
    1 vs 2, 1 vs 3, ..., 1 vs k, 2 vs 3, ..., 2 vs k, ..., k-1 vs k.

    sv_indices[0,...,nSV-1] are values in [1,...,num_traning_data] to
    indicate support vectors in the training set.

    label contains labels in the training data.

    nSV is the number of support vectors in each class.

    free_sv is a flag used to determine whether the space of SV should
    be released in free_model_content(struct svm_model*) and
    free_and_destroy_model(struct svm_model**). If the model is
    generated by svm_train(), then SV points to data in svm_problem
    and should not be removed. For example, free_sv is 0 if svm_model
    is created by svm_train, but is 1 if created by svm_load_model.

- Function: double svm_predict(const struct svm_model *model,
                               const struct svm_node *x);

    This function does classification or regression on a test vector x
    given a model.

    For a classification model, the predicted class for x is returned.
    For a regression model, the function value of x calculated using
    the model is returned. For an one-class model, +1 or -1 is

- Function: void svm_cross_validation(const struct svm_problem *prob,
	const struct svm_parameter *param, int nr_fold, double *target);

    This function conducts cross validation. Data are separated to
    nr_fold folds. Under given parameters, sequentially each fold is
    validated using the model from training the remaining. Predicted
    labels (of all prob's instances) in the validation process are
    stored in the array called target.

    The format of svm_prob is same as that for svm_train().

- Function: int svm_get_svm_type(const struct svm_model *model);

    This function gives svm_type of the model. Possible values of
    svm_type are defined in svm.h.

- Function: int svm_get_nr_class(const svm_model *model);

    For a classification model, this function gives the number of
    classes. For a regression or an one-class model, 2 is returned.

- Function: void svm_get_labels(const svm_model *model, int* label)

    For a classification model, this function outputs the name of
    labels into an array called label. For regression and one-class
    models, label is unchanged.

- Function: void svm_get_sv_indices(const struct svm_model *model, int *sv_indices)

    This function outputs indices of support vectors into an array called sv_indices.
    The size of sv_indices is the number of support vectors and can be obtained by calling svm_get_nr_sv.
    Each sv_indices[i] is in the range of [1, ..., num_traning_data].

- Function: int svm_get_nr_sv(const struct svm_model *model)

    This function gives the number of total support vector.

- Function: double svm_get_svr_probability(const struct svm_model *model);

    For a regression model with probability information, this function
    outputs a value sigma > 0. For test data, we consider the
    probability model: target value = predicted value + z, z: Laplace
    distribution e^(-|z|/sigma)/(2sigma)

    If the model is not for svr or does not contain required
    information, 0 is returned.

- Function: double svm_predict_values(const svm_model *model,
				    const svm_node *x, double* dec_values)

    This function gives decision values on a test vector x given a
    model, and return the predicted label (classification) or
    the function value (regression).

    For a classification model with nr_class classes, this function
    gives nr_class*(nr_class-1)/2 decision values in the array
    dec_values, where nr_class can be obtained from the function
    svm_get_nr_class. The order is label[0] vs. label[1], ...,
    label[0] vs. label[nr_class-1], label[1] vs. label[2], ...,
    label[nr_class-2] vs. label[nr_class-1], where label can be
    obtained from the function svm_get_labels. The returned value is
    the predicted class for x. Note that when nr_class = 1, this
    function does not give any decision value.

    For a regression model, dec_values[0] and the returned value are
    both the function value of x calculated using the model. For a
    one-class model, dec_values[0] is the decision value of x, while
    the returned value is +1/-1.

- Function: double svm_predict_probability(const struct svm_model *model,
	    const struct svm_node *x, double* prob_estimates);

    This function does classification or regression on a test vector x
    given a model with probability information.

    For a classification model with probability information, this
    function gives nr_class probability estimates in the array
    prob_estimates. nr_class can be obtained from the function
    svm_get_nr_class. The class with the highest probability is
    returned. For regression/one-class SVM, the array prob_estimates
    is unchanged and the returned value is the same as that of

- Function: const char *svm_check_parameter(const struct svm_problem *prob,
                                            const struct svm_parameter *param);

    This function checks whether the parameters are within the feasible
    range of the problem. This function should be called before calling
    svm_train() and svm_cross_validation(). It returns NULL if the
    parameters are feasible, otherwise an error message is returned.

- Function: int svm_check_probability_model(const struct svm_model *model);

    This function checks whether the model contains required
    information to do probability estimates. If so, it returns
    +1. Otherwise, 0 is returned. This function should be called
    before calling svm_get_svr_probability and

- Function: int svm_save_model(const char *model_file_name,
			       const struct svm_model *model);

    This function saves a model to a file; returns 0 on success, or -1
    if an error occurs.

- Function: struct svm_model *svm_load_model(const char *model_file_name);

    This function returns a pointer to the model read from the file,
    or a null pointer if the model could not be loaded.

- Function: void svm_free_model_content(struct svm_model *model_ptr);

    This function frees the memory used by the entries in a model structure.

- Function: void svm_free_and_destroy_model(struct svm_model **model_ptr_ptr);

    This function frees the memory used by a model and destroys the model
    structure. It is equivalent to svm_destroy_model, which
    is deprecated after version 3.0.

- Function: void svm_destroy_param(struct svm_parameter *param);

    This function frees the memory used by a parameter set.

- Function: void svm_set_print_string_function(void (*print_func)(const char *));

    Users can specify their output format by a function. Use
    for default printing to stdout.

Java Version

The pre-compiled java class archive `libsvm.jar' and its source files are
in the java directory. To run the programs, use

java -classpath libsvm.jar svm_train <arguments>
java -classpath libsvm.jar svm_predict <arguments>
java -classpath libsvm.jar svm_toy
java -classpath libsvm.jar svm_scale <arguments>

Note that you need Java 1.5 (5.0) or above to run it.

You may need to add Java runtime library (like to the classpath.
You may need to increase maximum Java heap size.

Library usages are similar to the C version. These functions are available:

public class svm {
	public static final int LIBSVM_VERSION=324;
	public static svm_model svm_train(svm_problem prob, svm_parameter param);
	public static void svm_cross_validation(svm_problem prob, svm_parameter param, int nr_fold, double[] target);
	public static int svm_get_svm_type(svm_model model);
	public static int svm_get_nr_class(svm_model model);
	public static void svm_get_labels(svm_model model, int[] label);
	public static void svm_get_sv_indices(svm_model model, int[] indices);
	public static int svm_get_nr_sv(svm_model model);
	public static double svm_get_svr_probability(svm_model model);
	public static double svm_predict_values(svm_model model, svm_node[] x, double[] dec_values);
	public static double svm_predict(svm_model model, svm_node[] x);
	public static double svm_predict_probability(svm_model model, svm_node[] x, double[] prob_estimates);
	public static void svm_save_model(String model_file_name, svm_model model) throws IOException
	public static svm_model svm_load_model(String model_file_name) throws IOException
	public static String svm_check_parameter(svm_problem prob, svm_parameter param);
	public static int svm_check_probability_model(svm_model model);
	public static void svm_set_print_string_function(svm_print_interface print_func);

The library is in the "libsvm" package.
Note that in Java version, svm_node[] is not ended with a node whose index = -1.

Users can specify their output format by

	your_print_func = new svm_print_interface()
		public void print(String s)
			// your own format

Building Windows Binaries

Windows binaries are available in the directory `windows'. To re-build
them via Visual C++, use the following steps:

1. Open a DOS command box (or Visual Studio Command Prompt) and change
to libsvm directory. If environment variables of VC++ have not been
set, type

"C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat"

You may have to modify the above command according which version of
VC++ or where it is installed.

2. Type

nmake -f clean all

3. (optional) To build shared library libsvm.dll, type

nmake -f lib

4. (optional) To build 32-bit windows binaries, you must
	(1) Setup "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars32.bat" instead of vcvars64.bat
	(2) Change CFLAGS in /D _WIN64 to /D _WIN32

Another way is to build them from Visual C++ environment. See details
in libsvm FAQ.

- Additional Tools: Sub-sampling, Parameter Selection, Format checking, etc.

See the README file in the tools directory.


Please check the file README in the directory `matlab'.

Python Interface

See the README file in python directory.

Additional Information

If you find LIBSVM helpful, please cite it as

Chih-Chung Chang and Chih-Jen Lin, LIBSVM : a library for support
vector machines. ACM Transactions on Intelligent Systems and
Technology, 2:27:1--27:27, 2011. Software available at

LIBSVM implementation document is available at

For any questions and comments, please email [email protected]

This work was supported in part by the National Science
Council of Taiwan via the grant NSC 89-2213-E-002-013.
The authors thank their group members and users
for many helpful discussions and comments. They are listed in

  • Release latest version on Central

    Release latest version on Central

    The latest version Version 3.21, December 2015 wasn't released on Central. 3.17/ 29-Aug-2013 02:36

    For java projects it's easier to fetch from Central than from GH.


    opened by davido 33
  • Reduce the code differences between C and Java versions

    Reduce the code differences between C and Java versions

    This patch reduces some trivial differences between the C and Java versions:

    • add some comments missing in the Java version
    • align some variable names to match the C version
    • import static Math.* to be able to use "exp" instead of "Math.exp"
    • import static libsvm.svm_params.* to get the constants such as C_SVC as in C
    • use NULL instead of null in m4

    this should make it easier in the future to keep the C and Java versions in sync.

    opened by kno10 7
  • Matlab: include 'svm.h' instead of '../svm.h'

    Matlab: include 'svm.h' instead of '../svm.h'

    The Matlab Makefile already has .. on the -I option for the compiler so this was not required. This was only required for the make.m Matlab and Octave script, so it was modified to include .. on the search path.

    This change is required to build the mex files using a libsvm library different than the one in this distribution. Maybe a system-wide install of libsvm, or just another version for testing.

    opened by carandraug 7
  • Checking for users before running program

    Checking for users before running program

    Hi again,

    I am using the lab machines at my university, but I don't want to inconvenience others if they are sitting there. I had some problems implementing that with your, but I discovered that I could reimplement most of the functionality (that I needed) through gnu parallel instead.

    #!/usr/bin/env bash
    LOGFILE=$(mktemp "XXXX.parallel.log")
    function unused {
        parallel --plain                                                \
                 --sshloginfile ..                                      \
                 --nonall                                               \
                 --tag                                                  \
                 '[[ -z $(users | sed "s/$USER//") ]] && echo "unused"' \
            | sed -e 's/\s*unused//'                                    \
                  -e 's/^/4\//'
    function exit_parallel {
        parallel --plain                                \
                 --sshloginfile ..                      \
                 --nonall                               \
                 'killall -q -u $USER svm-train'
        rm "$LOGFILE"
    trap 'echo "Ctrl-C detected.";                  \
              exit_parallel;                        \
              exit 130'                             \
    parallel --plain                                    \
             --sshloginfile <(unused)                   \
             --filter-hosts                             \
             --joblog "$LOGFILE"                        \
             --resume-failed                            \
             --timeout 28800                            \
             --tag                                      \
             'nice svm-train -q                         \
                             -m 1024                    \
                             -h 0                       \
                             -v 5                       \
                             -c $(echo 2^{1} | bc -l)   \
                             -g $(echo 2^{2} | bc -l)   \
                     "'$DATA'"                          \
                  | sed -e "s/Cross .* = //"            \
                        -e "s/%//"'                     \
             ::: {-5..15..2}                            \
             ::: {3..-15..-2}

    This does make some assumptions according to my environment (like the home folder always being the same on every machine). You also need to configure the script directly in the script. I just thought I would tell you as you might be interested in it (or someone else following this repository).

    opened by ljos 7
  • ERROR: to use other evaluation criteria, labels must be +1/-1

    ERROR: to use other evaluation criteria, labels must be +1/-1


    After adding the plug-in "eval.h" and "eval.cpp" used in crossvalidation with different criteria (AUC, F-score, etc.), there is an error when running "svm-predict" with heart_scale (the example data file): ERROR: to use other evaluation criteria, labels must be +1/-1 image

    I'm wondering what is the problem. Any help is appreciated. Thanks!

    opened by vincentjytsai-nycu 6
  • Zeroed weights for entire class

    Zeroed weights for entire class

    I know that it's weird usage of class weights, but stil, could it be explained somehow? Or fixed?


    0 1:0 2:0 3:0
    0 1:0 2:0 3:1
    0 1:0 2:1 3:0
    1 1:0 2:1 3:1
    1 1:1 2:0 3:0
    1 1:1 2:0 3:1
    2 1:1 2:1 3:0
    2 1:1 2:1 3:1


    libsvm-3.20$ ./svm-train -b 1 -w0 1 -w1 1 -w2 0 dataset.txt model
    libsvm-3.20$ ./svm-predict -b 1 dataset.txt model predictions.out

    It produces in predictions.out:

    labels 0 1 2
    2 3.31221e-14 3.30357e-14 1
    2 3.63995e-14 3.24543e-14 1
    2 3.36039e-14 3.30595e-14 1
    2 3.77311e-14 3.12876e-14 1
    2 3.86737e-14 2.78238e-14 1
    2 3.82377e-14 2.50579e-14 1
    2 3.84825e-14 2.96375e-14 1
    2 3.84239e-14 2.58019e-14 1
    opened by olologin 6
  • What value should the class label be in regression?

    What value should the class label be in regression?

    In the README it says:

    Each line contains an instance and is ended by a '\n' character. For classification,

    However, we found that the label doesn't need to be an integer on Linux, as it also works if you use a string. For instance, using UNK (from unknown) works - but not on Windows.

    To ensure a similar experience across operating systems, which default value is encouraged? Documentation says 'any integer', so can I just use 0?

    opened by BramVanroy 5
  • Make Matlab/Octave's svmpredict understand info().

    Make Matlab/Octave's svmpredict understand info().

    Currently svmpredict.c calls vm_set_print_string_function uselessly, since the only variable this function changes, svm_print_string, is not used anywhere in svmpredict.c, nor is the function info() used. Instead, prints are hardcoded to be mexPrintf. This causes an issue when one asks for validation and -q, whereby the -q is ignored, and output is still printed.

    This change makes info() in svm.cpp public via svm.h, renames it to svm_info for consistency, and makes svmpredict.c use svm_info for its validation output.

    Let me know if there's anything to change in this patch, or if there's a much better solution :)

    opened by fedelebron 5
  • Obtain the norm of the weight vector

    Obtain the norm of the weight vector

    Hi! Is there a way to obtain the "norm of the weight vector" when using a non-linear kernel?

    I am looking for the value sum_{i,j} alpha_i * alpha_j * y_j * y_k * k(x_i, x_j).


    opened by barucden 4
  • svm-scale returns an empty feature file in case of a single instance

    svm-scale returns an empty feature file in case of a single instance

    Hello, I did train a 3 classes model using RBF kernel with 13 features and 1104 instances which is attached as "Full_Train.txt" and when scaled between -1 and 1 it succeeds but it scales on the y-axis "Full_Train_scaled.txt". And when I scale a file with a single detection or instance during deployment "Classify.txt" it returns an empty feature file with only the label left "Classify_scale.txt".

    The command I'm using

     ./svm-scale -l -1 -u 1 Classify.txt>Classify_scale.txt

    If you can please tell me if I'm doing something wrong or how to scale over the feature array and produce a scaled single instance file.

    Thanks in Advance.

    opened by MTawfik93 4
  • E2285 Could not find a match for 'max<T>(int,long)'

    E2285 Could not find a match for 'max(int,long)'

    svm.cpp during build time, int max_iter = max(10000000, l>INT_MAX/100 ? INT_MAX : 100*l); //int max_iter = INT_MAX; //ready to change like this????

    E2285 Could not find a match for 'max(int,long)'

    I also get this issue from svm-train.c, case 'q': svm_set_print_string_function = &print_null; //Lvalue required???? //svm_set_print_string_function; //ready to change like this???? i--; break;

    Did I mess anything aside from compiling or building, I used 2.89 before now upgrade to 3.23 but error comes out. Any help?

    opened by blaisexen 4
  • Linux wheel support in github workflow

    Linux wheel support in github workflow

    Hello, I am wondering if there are plans on adding linux support in the provided wheel.yml file? Maybe this is related to @yxliu-ntu who initially added the github actions support.

    Are there also plans in automatically pushing created wheels to PyPi?

    opened by naetherm 4
  • Implement tbb-based parallelism; use repeatable random numbers.

    Implement tbb-based parallelism; use repeatable random numbers.

    This fork from the LibSVM 3.3 package incorporates the following enhancements:

    Implements parallelism in the get_Q() and svc_predict_values() functions. This requires that the tbb (thread building blocks) package be installed ("apt-get install -y libtbb-dev"). Initial performance tests on a 16-core machine indicate an elapsed time for a large training session to be reduced by a factor of 3 to 4.

    Uses the std::minstd_rand random number generator instead of the usual rand() and srand(). This allows for repeatable random numbers to be generated which is importand when implementing unit tests.

    opened by Roebu 4
  • MATLAB libsvm issue :same result when predicting

    MATLAB libsvm issue :same result when predicting

    林老师您好! I always get the same prediction value, even if I've already changed the inputdata. Specifically, I used 9 precipitation factors and real precipitation data from 1951 to 2010 to train the SVM regression model. Then I input the factors from 2011 to 2016 to the model in order to get the predicted precipitation data. But all I got was an array with the same 6 numberslike[248 248 248 248 248 248]. When I change the inputdata, the result may change but still an array with the same six numbers. Sometimes the result array can be 'almost' the same, like [222.121971040339 217.475177855453 221.321911068434 215.667836808570 222.829461145174]. It's also been found that only if I input the data that is very very closed to the trainnig data(1951-2010 factors), the result can be quite well. Ironically, when I use some classic dataset (from my reference books), the result will be pretty pretty good. Add on, RBF kernel was used. My version is MATLAB R2018a with libsvm-3.14.

    opened by Nuist-Lee 0
  • Importing scikit-learn SVM model to LIBSVM

    Importing scikit-learn SVM model to LIBSVM

    Hello, I have trained my SVM model for MNIST classification in Python using scikit-learn( Grid searchcv). I need to implement the SVM prediction in C language using the model parameters extracted in Python. I was wondering is there any way to import the trained model to LIBSVM ? Is it possible to use the model parameters (from python) in svm-predict of LIBSVM? Regards,

    opened by Afef00 1
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