eldo_user

Specifying Simulation Output
Incremental Saving of the JWDB Database
Thus the spacing of timepoints in the output file is generally non-constant. The
maximum average density of timepoints in the output file is determined by the
resolution parameter of the option. The minimum density is not guaranteed, neither
locally, nor globally. This option is an interesting alternative, combining the certainty
that the points in the output are computed points only (no interpolation error), and the
ability to handle low activity periods efficiently. It is however, generally not well suited
for simulations where an FFT must be computed, because of the non-constant spacing of
the timepoints (this would result in interpolation errors when re-sampling for the FFT).
• .OPTION INTERP=1 (in the Eldo Reference Manual)
Both OUT_STEP and OUT_RESOL options dump only computed points to the output
file. Sometimes it may be desirable to obtain equally spaced time points, but forcing
timepoints (with OUT_STEP for example) would result in an unacceptable CPU
penalty. In these cases, interpolating may be useful. An interpolation option is available
to force Eldo to sample the output data along the parameter of the .TRAN
command. If using the option INTERP=1, the transient output waveforms are
interpolated, and the timepoints written to the file are aligned with multiples of
exactly. For example, if using both the following:
.tran 1ns 100ns
.option interp=1
the output waveforms will contain exactly 101 points (time 0 is always included),
spaced by 1ns. Glitches shorter than 1ns may not be caught in the resulting waveform.
This is a radical way to reduce the size of the binary output files (.wdb). However, the
written data is obtained by interpolation, thus including an unpredictable amount of
interpolation error. During low-activity periods, Eldo still picks the largest possible
timesteps which enable the accuracy requirements to be met, and fills the output data
with interpolated data (at no or little cost, as opposed to the OUT_STEP technique
discussed previously).
Related Topics
Error and Warning Message Classification
Error and Warning Messages
Plotting, Printing and Probing
Incremental Saving of the JWDB Database
By default, Eldo sends simulation results to the JWDB server, which stores them in memory and
then generates the .wdb file at the end of the simulation. To invoke incremental saving, forcing
Eldo to save JWDB format simulation results in to a .wdb file before the end of the simulation,
invoke Eldo with the -jwdb_threshold argument. Simulation results will be saved each time the
simulation result size has reached threshold value (default is 100 MB).
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Eldo® User's Manual, 15.3