N-Gram

An N-gram is a sequence of N words: a 2-gram (or bigram) is a two-word sequence of words like “lütfen ödevinizi”, “ödevinizi çabuk”, or ”çabuk veriniz”, and a 3-gram (or trigram) is a three-word sequence of words like “lütfen ödevinizi çabuk”, or “ödevinizi çabuk veriniz”.

Smoothing

To keep a language model from assigning zero probability to unseen events, we’ll have to shave off a bit of probability mass from some more frequent events and give it to the events we’ve never seen. This modification is called smoothing or discounting.

Laplace Smoothing

The simplest way to do smoothing is to add one to all the bigram counts, before we normalize them into probabilities. All the counts that used to be zero will now have a count of 1, the counts of 1 will be 2, and so on. This algorithm is called Laplace smoothing.

Add-k Smoothing

One alternative to add-one smoothing is to move a bit less of the probability mass from the seen to the unseen events. Instead of adding 1 to each count, we add a fractional count k. This algorithm is therefore called add-k smoothing.

Video Lectures

For Developers

You can also see Java, Python, C, Cython, Swift, Js, or C# repository.

Requirements

• C++ Compiler
• Git

CPP

To check if you have compatible C++ Compiler installed,

• Open CLion IDE
• Preferences >Build,Execution,Deployment > Toolchain

Git

Install the latest version of Git.

Download Code

In order to work on code, create a fork from GitHub page. Use Git for cloning the code to your local or below line for Ubuntu:

git clone <your-fork-git-link>

A directory called DataStructure will be created. Or you can use below link for exploring the code:

git clone https://github.com/starlangsoftware/NGram-CPP.git

Open project with CLion IDE

To import projects from Git with version control:

• Open CLion IDE , select Get From Version Control.

• In the Import window, click URL tab and paste github URL.

• Click open as Project.

Result: The imported project is listed in the Project Explorer view and files are loaded.

Compile

From IDE

After being done with the downloading and opening project, select Build Project option from Build menu. After compilation process, user can run NGram-CPP.

Detailed Description

• Training NGram
• Using NGram
• Saving NGram
• Loading NGram

Training NGram

Boş bir NGram modeli oluşturmak için To create an empty NGram model:

NGram(int N)

For example,

a = NGram(2);

this creates an empty NGram model.

To add an sentence to NGram:

void addNGramSentence(Symbol[] symbols)

For example,

String[] text1 = {"jack", "read", "books", "john", "mary", "went"};
String[] text2 = {"jack", "read", "books", "mary", "went"};
nGram = new NGram<String>(2);
nGram.addNGramSentence(text1);
nGram.addNGramSentence(text2);

with the lines above, an empty NGram model is created and the sentences text1 and text2 are added to the bigram model.

NoSmoothing class is the simplest technique for smoothing. It doesn't require training. Only probabilities are calculated using counters. For example, to calculate the probabilities of a given NGram model using NoSmoothing:

a.calculateNGramProbabilities(new NoSmoothing());

LaplaceSmoothing class is a simple smoothing technique for smoothing. It doesn't require training. Probabilities are calculated adding 1 to each counter. For example, to calculate the probabilities of a given NGram model using LaplaceSmoothing:

a.calculateNGramProbabilities(new LaplaceSmoothing());

GoodTuringSmoothing class is a complex smoothing technique that doesn't require training. To calculate the probabilities of a given NGram model using GoodTuringSmoothing:

a.calculateNGramProbabilities(new GoodTuringSmoothing());

AdditiveSmoothing class is a smoothing technique that requires training.

a.calculateNGramProbabilities(new AdditiveSmoothing());

Using NGram

To find the probability of an NGram:

double getProbability(Symbol ... symbols)

For example, to find the bigram probability:

a.getProbability("jack", "reads")

To find the trigram probability:

a.getProbability("jack", "reads", "books")

Saving NGram

To save the NGram model:

void saveAsText(String fileName)

For example, to save model "a" to the file "model.txt":

a.saveAsText("model.txt");              

Loading NGram

To load an existing NGram model:

NGram(String fileName)

For example,

a = NGram("model.txt");

this loads an NGram model in the file "model.txt".

For Contibutors

Conan Setup

1. First install conan.

pip install conan

Instructions are given in the following page:

https://docs.conan.io/2/installation.html

2. Add conan remote 'ozyegin' with IP: 104.247.163.162 with the following command:

conan remote add ozyegin http://104.247.163.162:8081/artifactory/api/conan/conan-local --insert

3. Use the comman conan list to check for installed packages. Probably there are no installed packages.

conan list

conanfile.py file

1. Put the correct dependencies in the requires part

    requires = ["math/1.0.0", "classification/1.0.0"]

2. Default settings are:

    settings = "os", "compiler", "build_type", "arch"
    options = {"shared": [True, False], "fPIC": [True, False]}
    default_options = {"shared": True, "fPIC": True}
    exports_sources = "src/*", "Test/*"

    def layout(self):
        cmake_layout(self, src_folder="src")

    def generate(self):
        tc = CMakeToolchain(self)
        tc.generate()
        deps = CMakeDeps(self)
        deps.generate()

    def build(self):
        cmake = CMake(self)
        cmake.configure()
        cmake.build()

    def package(self):
        copy(conanfile=self, keep_path=False, src=join(self.source_folder), dst=join(self.package_folder, "include"), pattern="*.h")
        copy(conanfile=self, keep_path=False, src=self.build_folder, dst=join(self.package_folder, "lib"), pattern="*.a")
        copy(conanfile=self, keep_path=False, src=self.build_folder, dst=join(self.package_folder, "lib"), pattern="*.so")
        copy(conanfile=self, keep_path=False, src=self.build_folder, dst=join(self.package_folder, "lib"), pattern="*.dylib")
        copy(conanfile=self, keep_path=False, src=self.build_folder, dst=join(self.package_folder, "bin"), pattern="*.dll")

    def package_info(self):
        self.cpp_info.libs = ["ComputationalGraph"]

CMakeLists.txt file

1. Set the C++ standard with compiler flags.

	set(CMAKE_CXX_STANDARD 20)
	set(CMAKE_CXX_FLAGS "-O3")

2. Dependent packages should be given with find_package.

	find_package(util_c REQUIRED)
	find_package(data_structure_c REQUIRED)

3. For library part, use add_library and target_link_libraries commands. Use m library for math linker in Linux.

	add_library(Math src/Distribution.cpp src/Distribution.h src/DiscreteDistribution.cpp src/DiscreteDistribution.h src/Vector.cpp src/Vector.h src/Eigenvector.cpp src/Eigenvector.h src/Matrix.cpp src/Matrix.h src/Tensor.cpp src/Tensor.h)
	target_link_libraries(Math util_c::util_c data_structure_c::data_structure_c m)

4. For executable tests, use add_executable and target_link_libraries commands. Use m library for math linker in Linux.

	add_executable(DiscreteDistributionTest src/Distribution.cpp src/Distribution.h src/DiscreteDistribution.cpp src/DiscreteDistribution.h src/Vector.cpp src/Vector.h src/Eigenvector.cpp src/Eigenvector.h src/Matrix.cpp src/Matrix.h src/Tensor.cpp src/Tensor.h Test/DiscreteDistributionTest.cpp)
	target_link_libraries(DiscreteDistributionTest util_c::util_c data_structure_c::data_structure_c m)

Data files

1. Add data files to the cmake-build-debug folder.

C++ files

1. If needed, comparator operators == and < should be implemented for map and set data structures.

    bool operator==(const Word &anotherWord) const{
        return (name == anotherWord.name);
    }
    bool operator<(const Word &anotherWord) const{
        return (name < anotherWord.name);
    }

2. Do not forget to comment each function.

	/**
 	* A constructor of Word class which gets a String name as an input and assigns to the name variable.
	*
	* @param _name String input.
 	*/
	Word::Word(const string &_name) {

3. Function names should follow caml case.

	int Word::charCount() const

4. Write getter and setter methods.

	string Word::getName() const
	void Word::setName(const string &_name)

5. Use catch.hpp for testing purposes. Add

#define CATCH_CONFIG_MAIN  // This tells Catch to provide a main() - only do this in one cpp file

line in only one of the test files. Add

#include "catch.hpp"

line in all test files. Example test file is given below:

TEST_CASE("DictionaryTest") {
    TxtDictionary lowerCaseDictionary = TxtDictionary("lowercase.txt", "turkish_misspellings.txt");
    TxtDictionary mixedCaseDictionary = TxtDictionary("mixedcase.txt", "turkish_misspellings.txt");
    TxtDictionary dictionary = TxtDictionary();
    SECTION("testSize"){
        REQUIRE(29 == lowerCaseDictionary.size());
        REQUIRE(58 == mixedCaseDictionary.size());
        REQUIRE(62113 == dictionary.size());
    }
    SECTION("testGetWord"){
        for (int i = 0; i < dictionary.size(); i++){
            REQUIRE_FALSE(nullptr == dictionary.getWord(i));
        }
    }
    SECTION("testLongestWordSize"){
        REQUIRE(1 == lowerCaseDictionary.longestWordSize());
        REQUIRE(1 == mixedCaseDictionary.longestWordSize());
        REQUIRE(21 == dictionary.longestWordSize());
    }

6. Enumerated types should be declared with enum class.

	enum class Pos {
		ADJECTIVE,
		NOUN,
		VERB,
		ADVERB,

7. Every header file should start with

	#ifndef MATH_DISTRIBUTION_H
	#define MATH_DISTRIBUTION_H

and end with

	#endif //MATH_DISTRIBUTION_H

8. Do not forget to use const expression for parameters, if they will not be changed in the function.

	void Word::setName(const string &_name);

9. Do not forget to use const expression for methods, which do not modify any class attribute. Also use [[dodiscard]]

	[[nodiscard]] bool isPunctuation() const;

10. Use xmlparser package for parsing xml files.

    auto* doc = new XmlDocument("test.xml");
    doc->parse();
    XmlElement* root = doc->getFirstChild();
    XmlElement* firstChild = root->getFirstChild();

11. Data structures: Use map for hash map, unordered_map for linked hash map, vector for array list, unordered_set for hash set