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108 lines
3.9 KiB
Markdown
108 lines
3.9 KiB
Markdown
| [Home](/trick) → [Tutorial Home](Tutorial) → Running Real-Time |
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<!-- Section -->
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<a id=running-real-time></a>
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## Running Real-Time
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Recall that the cannonball run was 5.2 seconds, yet when the simulation ran, it
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was done in a flash of CPU time. This section will add real-time synchronization.
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### Making A Real-time Input File
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Similar to making a data recording file, a real-time input file is needed.
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```python
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trick.frame_log_on()
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trick.real_time_enable()
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trick.exec_set_software_frame(0.1)
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trick.itimer_enable()
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trick.exec_set_enable_freeze(True)
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trick.exec_set_freeze_command(True)
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trick.sim_control_panel_set_enabled(True)
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```
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**Listing 10 - Real Time File `realtime.py`**
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```bash
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% cd $HOME/trick_sims/SIM_cannon_analytic/Modified_data
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% vi realtime.py <edit and save>
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```
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Here is a brief explanation.
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`trick.frame_log_on()` - tells the simulation to log the performance of the
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simulation (i.e., how it is running with respect to the real-world time).
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`trick.real_time_enable()` - tells the simulation to run in real-time
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synchronization.
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`trick.exec_set_software_frame(0.1)` - tells the simulation the frequency of
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the "heartbeat" of the simulation. If the simulation were sending out packets of
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information to a graphics server, the "heartbeat" might be 50 HZ (0.02). Trick
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synchronizes with the system clock on multiples of the rt_software_frame. If it
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is beating the system clock, it pauses. If it is falling behind, it registers
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"timeouts" and attempts to catch up.
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`trick.itimer_enable()` - allows other processes to run while Trick is
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waiting for the beginning of the next software frame to start the simulation
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jobs. If interval timers are not used, Trick will spin waiting for the next beat.
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`trick.exec_set_freeze_command()` - brings up the simulation in a frozen
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(non-running) state.
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`trick.exec_set_enable_freeze()` - allows the user to toggle the simulation
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from a frozen state to a running state at will.
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`trick.sim_control_panel_set_enabled(True)` or
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`simControlPanel = trick.SimControlPanel() & trick.add_external_application(simControlPanel)`
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- brings up the simulation control panel GUI.
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The `realtime.py` file must be included in the RUN_test/input.py file. When
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finished, the latest version of the input file should look like the following:
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```python
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execfile("Modified_data/realtime.py")
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execfile("Modified_data/cannon.dr")
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trick.stop(5.2)
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```
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```bash
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% cd $HOME/trick_sims/SIM_cannon_analytic/RUN_test
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% vi input.py <edit and save>
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```
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### Using The Sim Control Panel
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Fire up the cannonball again.
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```bash
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% cd $HOME/trick_sims/SIM_cannon_analytic
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% ./S_main*.exe RUN_test/input.py &
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```
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The **simulation control panel** should popup now. In the `realtime.py` file, we
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instructed Trick to start in a **freeze** state. Currently, the ball is sitting
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in the base of the barrel. To fire it, the **Start** button must be clicked on
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the simulation control panel in the **Commands** box.
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1. Click **Start** on simulation control panel. The simulation will
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run in sync with real-time.
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1. Once the simulation is finished, click the **Exit** button.
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Some items to note about the simulation control panel for your future use:
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* You may freeze the simulation at any point, and then restart.
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* You may freeze the simulation, then "dump a checkpoint" of the current
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state. This state is reloadable (i.e., you may jump to a previous/future
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point in the sim by loading the appropriate checkpoint).
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* You may toggle between real-time and non-real-time.
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* If the simulation lags behind real-time, it will log these as overruns
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(does not complete all jobs during the software frame) and display them in
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the tiny box next to the simulation name. If the simulation overruns, the
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sim will run as fast as it can "to catch up" to where it should be.
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* Using the File menu at the top, you may set a freeze point in the future.
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---
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[Next Page](ATutTrickView)
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