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9 RUN MENU |
The Run menu is used to execute the electromagnetic simulation of the current model. When a simulation is started, memory is allocated to hold the mesh, which is the computational representation of the model, as well as the electromagnetic field values.
The simulation begins at time step zero, when all of the electromagnetic field values set to zero. As each time step passes, the fields are updated to their next state, and the sources, probes, and loads are evaluated. Because a copy of the model is created in a new form which is required by the simulation, updates to the model while the simulation is running do not change the simulation results.
Terminating the simulation will free the memory allocated for the simulation. A new simulation cannot be started until the previous one is terminated. Dismissing the simulation control dialog does not terminate a running simulation, but exiting the program will also terminate the simulation.
The simulation can be run by either using the simulation control dialog, or else from the Run menu items.
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Simulation... |
Display the simulation control dialog. |
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Start |
Start or continue the simulation |
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Stop |
Interrupt the simulation while it is running. |
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Reset |
Reset the simulation to its initial state. |
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Terminate |
Terminate the running simulation. |
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Checkpoint... |
Save the running simulation to a file. |
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Restart... |
Restart a checkpointed simulation. |
The Run Simulation dialog displays information about a running simulation, and also controls the simulation. The dialog contains three informational frames, plus an action area containing buttons which duplicate other Run menu items.
Most of the values displayed in this dialog have can be scaled to units selected from the list on the right-hand side of the value. The values cannot be modified directly within this dialog, but are calculated and displayed based upon the current model and execution environment.
9.1.1 Run Status Frame
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Start Time Step |
This is the current time step when the last Start was issued. |
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Current Time Step |
This is the current time step of the simulation. If iteration is proceeding, this value is updated every few seconds. |
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End Time Step |
This is the last time step that will complete the iteration. If the current time step and the end time step are the same, then iteration is complete and iteration may be restarted to extend the simulation. |
9.1.2 Resources Frame
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Memory Used
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These values show how much memory is currently in use by the program, and what the maximum amount of memory available is. Depending upon the operating system, the memory limit may be a user or job class limitation, or it may be the amount of physical memory not allocated to any other program on the system. |
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CPU Time Used
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These values show how much CPU time has been used, and what the CPU time limit enforced by the operating system is, if any. |
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CPUs Selected
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These values show how many CPUs will be used during the simulation, and how many are available in the system. CPUs are selected with the NCPUS (Cray UNICOS), PARALLEL (Solaris), or MP_SET_NUMTHREADS (SGI IRIX) environment variable. |
9.1.3 Simulation Frame
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Cell Size |
This is the size of each cell of the mesh. When the mesh is created, the current model is cut into cells of this size. The smaller the cell size, the more accurate the simulation, but each cell requires a fixed amount of memory (12 to 18 words). |
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Time Step |
This is the amount of time that passes during each time step. This value multiplied times the current time step is the current time of the simulation. |
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Mesh Dimensions |
This is the number of cells of the mesh for the X, Y, and Z dimensions. |
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Mesh Size |
This is the total number of cells in the mesh. |
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Memory Required |
This is an estimate of the amount of memory required to run the simulation. This value, plus the current size of the program, should be less than the memory limit. |
9.1.4 Action Area
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Start |
If no simulation is running, this button creates a new simulation and begins time stepping. If a simulation is running but has been interrupted by the Stop button, then Start will resume the previous time stepping. If the simulation has run to completion, a new time limit is set and the simulation continues. |
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Stop |
This button interrupts the time stepping of a simulation. This is useful for looking at intermediate results. The Start button will resume the simulation if the iteration is not complete. |
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Reset |
This button resets the simulation to its initial state. The time is set to zero, and all of the electromagnetic fields within the simulation are set to zero too. Sources and loads are returned to their initial conditions as well, and probes are reset such that the next Start will overwrite the previous results. |
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Terminate |
This button terminates a simulation. All resources that were allocated when the simulation was started are released. |
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Checkpoint... |
Save the currently running simulation to a file. The file will contain information about the size of the mesh, along with the current electric and magnetic vector field components. The mesh can later be restarted and continued for the same model. |
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Restart... |
Restart a checkpointed simulation. If a simulation is currently running, the new values will replace the current ones. Otherwise, a new simulation will be started. The model must correspond to the same mesh as when it was checkpointed. |
9.2 RUN START DIALOG
Enter the number of time steps to iterate to start or continue a simulation.
If no simulation is currently running, a simulation mesh is created from the current model and the simulation starts from time step zero. The end time step is set to the time step increment and iteration begins. If no time step increment is set, then a mesh is created but the simulation does not proceed.
If a simulation is currently running, a new end time step is set by adding the time step increment to the current time step and iteration proceeds until the limit is reached.
A running simulation can be interrupted during iteration with the Stop button. The Reset button will restore the simulation to its initial state. The Terminate button will terminate the simulation, thus allowing a new simulation to be started.
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Automatic Checkpointing |
If selected, then the simulation is saved periodically as the simulation runs. |
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Interval |
The number of time steps between automatic checkpoints. |
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Output Filename |
The name of the output file for automatic checkpointing. |
9.3 RUN RESET DIALOG
This action will discard the results of the current simulation and reset the simulation back to its initial state (time step zero).
The time is set to zero, and all of the electromagnetic fields within the simulation are set to zero too. Sources and loads are returned to their initial conditions as well, and probes are reset such that the next Start will overwrite the previous results.
Press "OK" to reset the simulation, or "Cancel" to leave the simulation at its current time.
This action will discard the results of the current simulation as well as free the computer resources allocated when the simulation was started.
Press "OK" to terminate the simulation, or "Cancel" to leave the simulation running at its current time.
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Write Sweep Output |
If set, then far field sweep data is calculated and written. |
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Delay Termination Until Iteration Complete |
During a long run which creates a large amount of far field sweep data, select this toggle for automatic termination at end of run. |
Information about the currently running simulation is saved to a checkpoint file. The simulation can later be restarted by reading the file.
Certain conditions must exist for a saved simulation to be successfully restarted. The current model at the time of the restart must be similar to the one active when the simulation was checkpointed. The mesh must be the exact same size, so the overall size of the model cannot change, nor can the mesh cell width. If the geometry blocks, sources, or loads of the restarting model are not the same as the original, some unusual electromagnetic phenomenon can result.
Probes can be arbitrarily different between the checkpoint and restart. No restrictions are set, although a restarted simulation will create new probe output files, overwriting (rather than extending) any existing files.
The computer architecture of the checkpointing and restarting computers must be similar; checkpoint files are not portable across diverse hardware implementations. Word size and floating point formats usually determine compatibility. For example, a run checkpointed on a 32-bit IEEE floating point format computer can be restarted on another, even one from a different manufacturer.
If a simulation is currently running, the checkpoint file is read and the run restarts at the time step of the saved simulation. If no simulation is running, then first a new simulation is started in the usual way, but without any initial time stepping. The field values from the checkpoint file are loaded, and the simulation is set to the saved time step.
If the model of the checkpointed file differs incompatibly from the current model at the time of the restart, then an error message is displayed and any running simulation is not affected.
When a simulation is terminated, the far field data is calculated. These calculations may take a long time if many angles and frequencies have been selected. As the calculation proceeds, the Write Sweeps dialog displays the status. To abort the far field calculations, press Cancel.