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# Material initialization

This function is called during the initialization phase of the simulation. You can use it to set up any necessary data structures or perform other initialization tasks, such as the inital state of the material and, if required, calculate material parameters.

This intialization function is called for both CPU and GPU implementations. Future implementations will enable the `runInitGPU` function when utilizing GPU acceleration.

## `runInit()`

    void runInit(UserMatInitCPU data) const

#### `data`

- Type: UserMatInitCPU
- Description: User material host data structure. See UserMatInitCPU for more information on the data structure.

## Example

    void MatMetal::runInit(UserMatInitCPU data) const
    {
        double young = data.p_cmat[1];
        double pr    = data.p_cmat[2];
        double bulk  = young / (3.0 * (1.0 - 2.0 * pr));
        double G     = young / (2.0 * (1.0 + pr));

        // Set material properties
        data.p_cmat[43] = bulk;

        // Stress-strain curve
        int idlc = static_cast<int>(round(data.p_cmat[6]));

        // Yield stress
        double sigy0 = data.p_history[3];

        // Set initial yield stress (if not already defined)
        if (sigy0 == 0.0) {
            // load material properties from database
            sigy0 = mat::load_curve(data.p_curve_data, data.p_curve_val, idlc, 0.0);
            data.p_history[3] = sigy0;
        }

        // Stiffness matrix
        data.p_stiffness[0] = G;
        data.p_stiffness[1] = bulk;
    }