Integers in Concrete are encrypted and processed according to a set of cryptographic parameters. By default, only a single set of such parameters are selected by Concrete Optimizer. This is not the best approach for every use case so multi parameters are introduced.
When they are enabled, a different set of parameters are selected for each bit-width in the circuit, which results in:
Faster execution (generally).
Slower key generation.
Larger keys.
Larger memory usage during execution.
To enable them, you can use parameter_selection_strategy=fhe.ParameterSelectionStrategy.MULTI configuration option.