m2cgen

m2cgen (Model 2 Code Generator) - is a lightweight library which provides an easy way to transpile trained statistical models into a native code (Python, C, Java, Go, JavaScript, Visual Basic, C#, PowerShell, R, PHP, Dart, Haskell, Ruby, F#).

• Installation
• Supported Languages
• Supported Models
• Classification Output
• Usage
• CLI
• FAQ

Installation

Supported Python version is >= 3.6.

pip install m2cgen

Supported Languages

• C
• C#
• Dart
• F#
• Go
• Haskell
• Java
• JavaScript
• PHP
• PowerShell
• Python
• R
• Ruby
• Visual Basic (VBA-compatible)

Supported Models

You can find versions of packages with which compatibility is guaranteed by CI tests here. Other versions can also be supported but they are untested.

Classification Output

Linear / Linear SVM / Kernel SVM

Binary

Scalar value; signed distance of the sample to the hyperplane for the second class.

Multiclass

Vector value; signed distance of the sample to the hyperplane per each class.

Comment

The output is consistent with the output of LinearClassifierMixin.decision_function.

SVM

Binary

Scalar value; signed distance of the sample to the hyperplane for the second class.

Multiclass

Vector value; one-vs-one score for each class, shape (n_samples, n_classes * (n_classes-1) / 2).

Comment

The output is consistent with the output of BaseSVC.decision_function when the decision_function_shape is set to ovo.

Tree / Random Forest / Boosting

Binary

Vector value; class probabilities.

Multiclass

Vector value; class probabilities.

Comment

The output is consistent with the output of the predict_proba method of DecisionTreeClassifier / ExtraTreeClassifier / ExtraTreesClassifier / RandomForestClassifier / XGBRFClassifier / XGBClassifier / LGBMClassifier.

Usage

Here's a simple example of how a linear model trained in Python environment can be represented in Java code:

from sklearn.datasets import load_boston
from sklearn import linear_model
import m2cgen as m2c

boston = load_boston()
X, y = boston.data, boston.target

estimator = linear_model.LinearRegression()
estimator.fit(X, y)

code = m2c.export_to_java(estimator)

Generated Java code:

public class Model {

    public static double score(double[] input) {
        return (((((((((((((36.45948838508965) + ((input[0]) * (-0.10801135783679647))) + ((input[1]) * (0.04642045836688297))) + ((input[2]) * (0.020558626367073608))) + ((input[3]) * (2.6867338193449406))) + ((input[4]) * (-17.76661122830004))) + ((input[5]) * (3.8098652068092163))) + ((input[6]) * (0.0006922246403454562))) + ((input[7]) * (-1.475566845600257))) + ((input[8]) * (0.30604947898516943))) + ((input[9]) * (-0.012334593916574394))) + ((input[10]) * (-0.9527472317072884))) + ((input[11]) * (0.009311683273794044))) + ((input[12]) * (-0.5247583778554867));
    }
}

You can find more examples of generated code for different models/languages here.

CLI

m2cgen can be used as a CLI tool to generate code using serialized model objects (pickle protocol):

$ m2cgen <pickle_file> --language <language> [--indent <indent>] [--function_name <function_name>]
         [--class_name <class_name>] [--module_name <module_name>] [--package_name <package_name>]
         [--namespace <namespace>] [--recursion-limit <recursion_limit>]

Don't forget that for unpickling serialized model objects their classes must be defined in the top level of an importable module in the unpickling environment.

Piping is also supported:

$ cat <pickle_file> | m2cgen --language <language>

FAQ

Q: Generation fails with RuntimeError: maximum recursion depth exceeded error.

A: If this error occurs while generating code using an ensemble model, try to reduce the number of trained estimators within that model. Alternatively you can increase the maximum recursion depth with sys.setrecursionlimit(<new_depth>).

Q: Generation fails with ImportError: No module named <module_name_here> error while transpiling model from a serialized model object.

A: This error indicates that pickle protocol cannot deserialize model object. For unpickling serialized model objects, it is required that their classes must be defined in the top level of an importable module in the unpickling environment. So installation of package which provided model's class definition should solve the problem.

Q: Generated by m2cgen code provides different results for some inputs compared to original Python model from which the code were obtained.

A: Some models force input data to be particular type during prediction phase in their native Python libraries. Currently, m2cgen works only with float64 (double) data type. You can try to cast your input data to another type manually and check results again. Also, some small differences can happen due to specific implementation of floating-point arithmetic in a target language.