PDFxTMDLib is a high-performance C++ library for parton distribution functions (PDFs) that integrates both collinear PDFs (cPDFs) and transverse momentum-dependent PDFs (TMDs). It is designed with modern C++17 principles to achieve excellent performance and extensibility. The library provides interfaces for reading PDF grid files and supports standard formats from LHAPDF and TMDLib, while allowing adaptability to non-standard formats.

For a comprehensive understanding of PDFxTMDLib, please refer to the full paper available on https://arxiv.org/abs/2412.16680.

• Unified interface for collinear PDFs and TMDs
• Type-erased interfaces for easy extension
• Factory design pattern for simple instantiation
• Cross-platform support (Linux and Windows)
• Thread-safety
• Optional Fortran and python wrappers

1. C++17 compatible compiler
2. CMake 3.30 or higher
3. Install g++:

   sudo apt install g++

1. Download the .deb file from the Releases section of GitHub. For example, download the current release: PDFxTMDLib-0.1.1-Linux.deb.
2. Install with:

   sudo dpkg -i PDFxTMDLib-0.3.0-Linux.deb

# Clone the repository
git clone https://github.com/Raminkord92/PDFxTMD.git
cd PDFxTMD

# Create build directory
mkdir build && cd build

# Configure with CMake
cmake .. -DCMAKE_BUILD_TYPE=Release

# Build and install
make
sudo make install

Create a main.cpp file with the following code:

#include <iostream>
#include <PDFxTMDLib/Factory.h>

int main()
{
    using namespace PDFxTMD;
    GenericCPDFFactory cPDF;
    auto CJ12min = cPDF.mkCPDF("CJ12min", 0);
    double x = 0.01;
    double mu2 = 100;
    std::cout << "Up quark PDF: " << CJ12min.pdf(PartonFlavor::u, x, mu2) << std::endl;

    return 0;
}

Compile the program using the following command:

g++ main.cpp -lPDFxTMDLib -o test.out

Run the compiled program:

./test.out

Here is a simple example of how to use PDFxTMDLib:

// TMD example
using namespace PDFxTMD;
GenericTMDFactory PBTMDObj;
auto PBTMDObj_ = PBTMDObj.mkTMD("PB-NLO-HERAI+II-2023-set2-qs=0.74", 0);
double x = 0.0001;
double kt2 = 10;
double mu2 = 100;
double gPBTMD = PBTMDObj_.tmd(PartonFlavor::g, x, kt2, mu2);
std::cout << "Gluon TMD of PB is: " << gPBTMD << std::endl;

// Collinear PDF example
GenericCPDFFactory ct18Obj;
auto ct18Obj_ = ct18Obj.mkCPDF("CT18NLO", 0);
double gCt18Obj_ = ct18Obj_.pdf(PartonFlavor::g, x, mu2);
std::cout << "Gluon PDF of CT18 is: " << gCt18Obj_ << std::endl;

Retrieve PDFs for all flavors simultaneously:

std::array<double, DEFAULT_TOTAL_PDFS> allFlavors;
CJ12min.pdf(x, mu2, allFlavors);

// Access individual flavors from the array
for (int i = 0; i < DEFAULT_TOTAL_PDFS; i++) {
    std::cout << "Flavor " << i << ": " << allFlavors[i] << std::endl;
}

Create PDFs with specific reader, interpolator, and extrapolator components:

using PDFTag = PDFxTMD::CollinearPDFTag;
using ReaderType = PDFxTMD::CDefaultLHAPDFFileReader;
using InterpolatorType = PDFxTMD::CLHAPDFBicubicInterpolator;
using ExtrapolatorType = PDFxTMD::CErrExtrapolator;

// Create custom PDF with specific components
PDFxTMD::GenericPDF<PDFTag, ReaderType, InterpolatorType, ExtrapolatorType> 
    customPDF("MMHT2014lo68cl", 0);

PDFxTMD::CouplingFactory couplingFactory;
auto coupling = couplingFactory.mkCoupling("MMHT2014lo68cl");
std::cout << "Alpha_s at mu2=100: " << coupling.AlphaQCDMu2(100) << std::endl;

For more comprehensive examples, please refer to the tutorial.cpp file in the examples directory, which demonstrates various approaches to using the library features.

PDFxTMDLib uses YAML configuration files to locate PDF sets:

• Windows: C:\ProgramData\PDFxTMDLib\config.yaml
• Linux: ~/.PDFxTMDLib/config.yaml

Example configuration:

paths: "/home/user/pdfs|/usr/share/PDFxTMDLib/pdfs"

Multiple paths can be specified with the | separator. By default, the current directory and \usr\local\share\PDFxTMD (linux) or C:\ProgramData\PDFxTMDLib\ (Windows) are already included.

PDFxTMDLib is optimized for high performance. The library includes benchmarking tools to compare PDFxTMDLib with other libraries like LHAPDF and TMDLib in the performance_vs_LHAPDF_TMDLIB directory, where the results are shown in the article https://arxiv.org/abs/2412.16680,

For visualization of PDFs and TMDs, you can use the QtPDFxTMDPlotter, a Qt-based graphical tool built on top of PDFxTMDLib. This tool provides an intuitive interface for plotting and comparing different PDF and TMD sets, making it easier to visualize and analyze the distributions.

Contributions are welcome! If you are interested in contributing, please don't hesitate to contact me at raminkord92@gmail.com.

This project is licensed under the Creative Commons Attribution 4.0 International License. For more details, please see the LICENSE file.

For any inquiries, please contact raminkord92@gmail.com.