How to use checkpoint/restore

The checkpoint and restore commands will save and restore the simulator state within the same invocation of vsim or between vsim sessions.

If you want to restore while running vsim, use the restore command; we call this a "warm restore". If you want to start up vsim and restore a previously-saved checkpoint, use the -restore switch with the vsim command; we call this a "cold restore".

Note: Checkpoint/restore allows a cold restore, followed by simulation activity, followed by a warm restore back to the original cold-restore checkpoint file. Warm restores to checkpoint files that were not created in the current run are not allowed except for this special case of an original cold restore file.

The things that are saved with checkpoint and restored with the restore command are:

• simulation kernel state
• vsim.wlf file
• signals listed in the list and wave windows
• file pointer positions for files opened under VHDL
• file pointer positions for files opened by the Verilog $fopen system task
• state of foreign architectures

Things that are NOT restored are:

• state of macros
• changes made with the command-line interface (such as user-defined Tcl commands)
• state of graphical user interface windows
• toggle statistics

In order to save the simulator state, use the command

checkpoint <filename> 

To restore the simulator state during the same session as when the state was saved, use the command:

restore <filename> 

To restore the state after quitting ModelSim, invoke vsim as follows:

vsim -restore <filename> [-nocompress] 

The checkpoint file is normally compressed. If there is a need to turn off the compression, you can do so by setting a special Tcl variable. Use:

set CheckpointCompressMode 0 

to turn compression off, and turn compression back on with:

set CheckpointCompressMode 1 

You can also control checkpoint compression using the modelsim.ini file in the [vsim] section (use the same 0 or 1 switch):

[vsim]
CheckpointCompressMode = <switch> 

If you use the foreign interface, you will need to add additional function calls in order to use checkpoint/restore. See the FLI Reference Manual for more information.

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