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Monte Carlo Analysis
Monte Carlo Basic Features
Tips for Improving Simulation Performance
Monte Carlo Incremental Approach
The overall Monte Carlo analysis run is made of several batches of simulations. Using an
incremental approach provides gradually an insight into the spread of distribution.
In Eldo, you control the sample size n and optionally, how the sampling is generated. In this
example, 100 simulations are requested by including the following statement in the netlist
description:
* Monte Carlo Analysis
.MC 100 SAVE=mc_file RESTART=mc_file
The additional SAVE/RESTART arguments are used to save the random sampling and the
simulated characteristics (see “Tips for Improving Simulation Performance” on page 1259).
These quantities can be used in subsequent Monte Carlo experiments. SAMPLING=LHS is
disabled when RESTART is specified.
Tip
See “.MC” in the Eldo Reference Manual.
Monte Carlo Analysis With a Varying Circuit
When you specify Monte Carlo analysis, Eldo performs the complete Monte Carlo analysis
after each change of the circuit parameters or the circuit’s configuration.
The probability distribution of a random variable may depend on the values of some circuit
parameters. For instance, the temperature of a MOS device affects the device’s threshold
voltage. After each change of the circuit parameters, Eldo recomputes the probability
distributions of the random variables, then performs the specified Monte Carlo analysis using an
appropriate set of input samples.
The probability distribution of a random variable may also depend on the circuit’s
configuration, which you can alter using .ALTER statements. Eldo performs a separate Monte
Carlo analysis for each configuration specified in the netlist, starting with the unmodified
netlist.
The results of each Monte Carlo analysis follow the corresponding change of circuit parameters
or netlist modification in the .chi file. If you requested detailed statistical outputs, the results of
the ith Monte Carlo analysis are also contained in the file _.mcm. The optional
output files _.mci and _.mco contain tables of the input and output
samples for the ith Monte Carlo analysis.
For example, the following netlist specifies Monte Carlo analysis with a sweep of a circuit
parameter PVG through 7 values:
Eldo® User's Manual, 15.3 419