**description:**Defines integration parameters and begins integration. Allows specifying the integration time step, the total time to integrate, and other conditions of integration.**example:**&integrate dt_integration = 1e-12, start_time = 0, finish_time = 5e-9, status_interval = 128, space_charge = 1 &end

Starts integration of equations for particles and fields at a simulated time of 0, taking steps of 1ps, until reaching 5ns. Every 128 steps, status information is printed to the screen. Space charge is included.**synopsis and defaults:**&integrate double dt_integration = 0; double start_time = 0; double finish_time = 0; long status_interval = -1; long space_charge = 0; long check_divergence = 0; double smoothing_parameter = 0; double J_filter_multiplier = 0; long terminate_on_total_loss = 0; STRING status_output = NULL; STRING lost_particles = NULL; &end

**details:**`dt_integration`: Simulation step size in seconds.`start_time`: Simulation start time. Typically 0 for new runs. Ignored for runs that involve fields loaded from other simulations.`finish_time`: Simulation stop time.`status_interval`: Interval in units of a simulation step between status printouts.`space_charge`: Flag requesting inclusion of space-charge in the simulation.`check_divergence`: Flag requesting that status printouts include a check of the field values using the divergence equation.`smoothing_parameter`: Specifies a simple spatial filter for the current density. The smoothing parameter, , is used to compute two new quantities, and . The program smooths longitudinal variation for constant radius, using , where is the central value and are the adjacent values to a grid point. This function is rarely used and I do not recommend it.`J_filter_multiplier`: Specifies a simple time-domain filter for the current density. For each point on the grid, the new current density value is replaced by . This is an infinite impulse response filter. This function is rarely used and I do not recommend it.`terminate_on_total_loss`: Flag requesting that when all simulation particles are lost (e.g., by hitting a wall or exiting the simulation), the simulation should terminate.`status_output`: Provide the name of a file to which to write status information, including statistics on the beams and fields. File is in SDDS format.`lost_particles`: Provide the name of a file to which to write information about particles that get lost. File is in SDDS format.