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Global Control

The general simulation parameters can be defined by the global block. This operator allows to define all control parameters such as the time step, the log/dump/restart frequencies, the log type, and any additional parameter that can be taken as an input by operators called during the simulation. 

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simulation:
  name: MySimulation
  body:
    - print_logo_banner                                  
    - hw_device_init                                     
    - make_empty_grid                                     
    - grid_flavor                                         
    - global                                             
    - [...]
    - simulation_epilog
    - hw_device_finalize

Below is the default definition of the global block as defined in data/config/config_globals.msp (included by default via main-config.msp):

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######################################################################################################
######################################### Default global block  ######################################
######################################################################################################

global:
  max_iteration: 1000                            # number of timesteps
  start_iteration: 0                             # number of timesteps  
  rcut_inc: 1.0 ang                              # skin distance for neighbor list 
  timestep: 0                                    # starting timestep
  physical_time: 0.                              # starting physical time
  dt: 1.0e-3 ps                                  # timestep
  log_mode: mechanical                           # set to chemistry or default

  simulation_restart_frequency: 1000             # restart frequency
  simulation_snapshot_frequency: 1000            # snapshot frequency  
  simulation_analysis_frequency: 1000            # analysis frequency
  simulation_thermostate_file_frequency: 10      # thermostate to file frequency
  thermostate_file: "thermodynamic_state.csv"    # default name of .csv thermostate file
  simulation_thermostate_screen_frequency: 10    # thermostate to screen frequency

  simulation_load_balance_frequency: 100         # load balancing frequency
  enable_load_balance: true                      # enable load balancing
  trigger_cost_model_fitting: false              # for load balancing
  cost_model_coefs: [ 0.0 , 0.0 , 1.0 , 0.0 ]    # for load balancing (RCB)
  enable_grid_compact: true                      # Enable array shrinking of particle arrays
  init_temperature: -1.0
  scale_temperature: -1.0
  md_loop_continue: true                         # needed for the computation loop to start
  trigger_thermo_state: true                     # needed to get the initial thermo state

######################################################################################################
######################################################################################################
Parameters' description
Parameter Description Type Default
max_iteration Ending time-step (maximum number of iterations) int 1000
start_iteration Starting iteration count int 0
rcut_inc Extra distance beyond cutoff (neighbor list skin) float 1.0 ang
timestep Starting time-step value int 0
physical_time Starting physical time float 0.
dt Time-step float 1.0e-3 ps
log_mode Log mode string mechanical (other choices are default or chemistry)
simulation_restart_frequency Restart file write frequency int 1000
simulation_snapshot_frequency Snapshot file write frequency int 1000
simulation_analysis_frequency On-the-fly analysis frequency int 1000
simulation_thermostate_file_frequency Thermodynamic state file write frequency int 10
thermostate_file Name of the thermodynamic state .csv file string "thermodynamic_state.csv"
simulation_thermostate_screen_frequency Thermodynamic state screen-print frequency int 10
simulation_load_balance_frequency Load balancing frequency int 100
enable_load_balance Enables load balancing bool true
trigger_cost_model_fitting Triggers automatic load-balancing cost model fitting bool false
cost_model_coefs Load-balancing cost model coefficients (RCB) list [ 0.0 , 0.0 , 1.0 , 0.0 ]
enable_grid_compact Enables grid memory compaction bool true
init_temperature Initial temperature (disabled if negative) float -1.0
scale_temperature Temperature scaling factor (disabled if negative) float -1.0
md_loop_continue Needed for the simulation loop to start bool true
trigger_thermo_state Needed to get the initial thermodynamic state bool true

In practice, the user doesn't need to think about some of these variables as they only serve as input for the simulation initialization. Here's a minimal global block you can use to start your simulation with.

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global:
  max_iteration: 1000                            # number of timesteps
  rcut_inc: 1.0 ang                              # skin distance for neighbor list 
  dt: 1.0e-3 ps                                  # timestep
  simulation_restart_frequency: 1000             # restart frequency
  simulation_snapshot_frequency: 1000            # snapshot frequency  
  simulation_analysis_frequency: 0               # analysis frequency
  simulation_thermostate_file_frequency: 10      # thermostate to file frequency
  thermostate_file: "thermodynamic_state.csv"    # default name of .csv thermostate file
  simulation_thermostate_screen_frequency: 10    # thermostate to screen frequency