Current Diagnostic Capabilities

Oct 13, 2025 by ludoplayers7.com 65 views

Introduction

VMEC++ is a widely used numerical code for solving the ideal magnetohydrodynamic (MHD) equilibrium equations. It is a powerful tool for modeling and analyzing the behavior of toroidal plasmas in magnetic confinement devices. One of the key features of VMEC++ is its ability to provide detailed diagnostic information about the equilibrium solution, including quantities such as the magnetic field, pressure, and current density. However, some of this information is only available as transient screen output, making it difficult to track and analyze the convergence of the solution. In this article, we will discuss how to add a progress or convergence group to VMEC++'s OutputQuantities, allowing for more detailed and accessible diagnostic information.

Background

VMEC++ is a numerical code that solves the ideal MHD equilibrium equations using a finite-element method. The code is designed to model the behavior of toroidal plasmas in magnetic confinement devices, such as tokamaks and stellarators. One of the key challenges in using VMEC++ is ensuring that the solution converges to a stable equilibrium. This requires careful tuning of the code's parameters and monitoring of the solution's behavior over time.

Current Diagnostic Capabilities

VMEC++ provides a range of diagnostic capabilities, including the ability to output quantities such as the magnetic field, pressure, and current density. However, some of this information is only available as transient screen output, making it difficult to track and analyze the convergence of the solution. For example, the fsq* quantities, which are used to monitor the convergence of the solution, are only available as screen output during the simulation.

Adding a `progress` or `convergence` Group to OutputQuantities

To add a progress or convergence group to VMEC++'s OutputQuantities, we need to modify the code's output routines to include these quantities. This can be done by adding new output groups to the OutputQuantities class, which is responsible for managing the output of diagnostic information.

Modifying the `OutputQuantities` Class

To add a progress or convergence group to the OutputQuantities class, we need to modify the code as follows:

// Add a new output group for the progress/convergence quantities
class OutputQuantities {
public:
    // ...
    void add_group(const std::string& name, const std::vector<std::string>& quantities) {
        // ...
        if (name == "progress") {
            // Add the progress/convergence quantities to the output group
            for (const auto& quantity : quantities) {
                if (quantity == "fsq*") {
                    // Add the fsq* quantities to the output group
                    output_groups[name].push_back(quantity);
                }
            }
        }
        // ...
    }
    // ...
};

Adding the `progress` or `convergence` Group to the Output File

Once we have modified the OutputQuantities class to include the progress or convergence group, we need to add this group to the output file. This can be done by modifying the code as follows:

// Add the progress/convergence group to the output file
void OutputQuantities::write_output_file(const std::string& filename) {
    // ...
    if (output_groups.find("progress") != output_groups.end()) {
        // Write the progress/convergence quantities to the output file
        for (const auto& quantity : output_groups["progress"]) {
            // ...
        }
    }
    // ...
}

Example Use Case

To demonstrate the use of the progress or convergence group, let's consider an example use case. Suppose we are running a VMEC++ simulation to model the behavior of a tokamak plasma. We want to track the convergence of the solution over time, but we only have access to the fsq* quantities as transient screen output. By adding a progress or convergence group to the output quantities, we can access these quantities in a more convenient and accessible way.

Benefits of Adding a `progress` or `convergence` Group

Adding a progress or convergence group to VMEC++'s OutputQuantities provides several benefits, including:

Improved diagnostic capabilities: By adding a progress or convergence group, we can access diagnostic information about the solution's convergence in a more convenient and accessible way.
Enhanced analysis capabilities: With the ability to track the convergence of the solution over time, we can perform more detailed and accurate analyses of the simulation results.
Increased productivity: By automating the process of tracking the convergence of the solution, we can reduce the time and effort required to analyze the simulation results.

Conclusion

Q: What is the purpose of adding a `progress` or `convergence` group to VMEC++'s OutputQuantities?

A: The purpose of adding a progress or convergence group to VMEC++'s OutputQuantities is to provide more detailed and accessible diagnostic information about the solution's convergence over time. This allows users to track the convergence of the solution and perform more detailed and accurate analyses of the simulation results.

Q: How do I modify the `OutputQuantities` class to include the `progress` or `convergence` group?

A: To modify the OutputQuantities class to include the progress or convergence group, you need to add a new output group to the class and modify the add_group method to include the progress or convergence quantities. You can do this by adding the following code to the OutputQuantities class:

// Add a new output group for the progress/convergence quantities
class OutputQuantities {
public:
    // ...
    void add_group(const std::string& name, const std::vector<std::string>& quantities) {
        // ...
        if (name == "progress") {
            // Add the progress/convergence quantities to the output group
            for (const auto& quantity : quantities) {
                if (quantity == "fsq*") {
                    // Add the fsq* quantities to the output group
                    output_groups[name].push_back(quantity);
                }
            }
        }
        // ...
    }
    // ...
};

Q: How do I add the `progress` or `convergence` group to the output file?

A: To add the progress or convergence group to the output file, you need to modify the write_output_file method to include the progress or convergence quantities. You can do this by adding the following code to the OutputQuantities class:

// Add the progress/convergence group to the output file
void OutputQuantities::write_output_file(const std::string& filename) {
    // ...
    if (output_groups.find("progress") != output_groups.end()) {
        // Write the progress/convergence quantities to the output file
        for (const auto& quantity : output_groups["progress"]) {
            // ...
        }
    }
    // ...
}

Q: What are the benefits of adding a `progress` or `convergence` group to VMEC++'s OutputQuantities?

A: The benefits of adding a progress or convergence group to VMEC++'s OutputQuantities include:

Improved diagnostic capabilities: By adding a progress or convergence group, you can access diagnostic information about the solution's convergence in a more convenient and accessible way.
Enhanced analysis capabilities: With the ability to track the convergence of the solution over time, you can perform more detailed and accurate analyses of the simulation results.
Increased productivity: By automating the process of tracking the convergence of the solution, you can reduce the time and effort required to analyze the simulation results.

Q: How do I use the `progress` or `convergence` group in my VMEC++ simulation?

A: To use the progress or convergence group in your VMEC++ simulation, you need to add the following code to your input file:

// Add the progress/convergence group to the output quantities
output_quantities.add_group("progress", {"fsq*"});

This will add the progress or convergence group to the output quantities and allow you to track the convergence of the solution over time.

Q: Can I customize the `progress` or `convergence` group to include other quantities?

A: Yes, you can customize the progress or convergence group to include other quantities by modifying the add_group method to include the desired quantities. For example, you can add the following code to the OutputQuantities class to include the fsq quantity:

// Add the fsq quantity to the progress/convergence group
if (name == "progress") {
    // Add the fsq quantity to the output group
    output_groups[name].push_back("fsq");
}

This will add the fsq quantity to the progress or convergence group and allow you to track the convergence of the solution over time.