CIF 3

Simplify values (optimized)

This CIF to CIF transformation simplifies CIF specifications, by applying same value-related simplifications as the Simplify values CIF to CIF transformation, but with optimizations for literal expressions.

Supported specifications

This transformation supports a subset of CIF specifications. The following restrictions apply:

  • Component definitions and component instantiations are not supported.

Preprocessing

No preprocessing is currently performed by this CIF to CIF transformation. To increase the subset of specifications that can be transformed, apply the following CIF to CIF transformations (in the given order):

Implementation details

One of the simplifications that the CIF to CIF transformation to Simplify values performs, is the evaluation of constant (sub-)expressions. For large literal expressions, such as arrays with thousands or even millions of elements, this is expensive, without having any effect. For instance, consider list/array literal [1, 2, 3]. Evaluating the list/array and the integer elements, and then reconstructing the literal list/array expression and literal integer expressions, has no effect. The result is the same list/array literal as the original.

This transformation detects literal expressions, and doesn’t further simplify them, thus greatly improving performance for large literal expressions. Literal expressions are detected using a static analysis. Due to using static analysis, some literals may not be simplified, while they would have been simplified if this literal detection optimization was not used. For instance, a set literal {1, 2, 1} is simplified to {1, 2} without optimizations, and is not simplified with optimizations. In this case, static analysis does not account for duplicate elements of the set.

The following differences can be observed for literal optimization, with respect to not using literal optimization:

  • Negations of integer literals are not normalized, although this only affects the internal representation of negative integer values, and may not be externally visible to end users.
  • Real literals are not normalized. For instance, 1e3 is not normalized to 1000.0.
  • For set literals, duplicate elements are not removed.
  • For dictionary literals, duplicate keys are not removed, and the dictionary literal is not further simplified. Without literal optimization, duplicate keys would lead to an error during simplification.

Renaming

n/a

Size considerations

This transformation tries to simplify the specification, possibly reducing its size.

All uses of constants lead to constant (sub-)expressions, and they are evaluated. This leads to constants being inlined. For constants with large literal values, this may significantly increase the size of the specification, especially if the constant is used more than once. For information on how to prevent this, see the Simplify values (no references, optimized) CIF to CIF transformation.

Optimality

Not all simplifications that could potentially be performed are implemented in this transformation.

The optimizations for literals that are performed influence the optimality of the simplification, as described above.