++ed by:
DMOL

1 PAUSE user

Moritz Lenz
and 1 contributors

NAME

Math::Expression::Evaluator::Optimizer - Optimize Math::Expression::Evaluator ASTs

SYNOPSIS

    use Math::Expression::Evaluator;
    my $m = Math::Expression::Evaluator->new("2 + 4*f");
    $m->optimize();
    for (0..100){
        print $m->val({f => $_}), "\n";
    }

DESCRIPTION

Math::Expression::Evaluator::Optimizer performs simple optimizations on the abstract syntax tree from Math::Expression::Evaluator.

You should not use this module directly, but interface it via Math::Expression::Evaluator.

The following optimizations are implemented:

  • Constant sub expressions: variable + 3 * 4 is simplfied to variable + 12.

  • Joining of constants in mixed constant/variable expressions: 2 + var + 3 is simplified to var + 5. Works only with sums and products (but internally a 2 - 3 + x is represented as 2 + (-3) + x, so it actually works with differences and divisions as well).

  • Flattening of nested sub expression: a * (3 * b) is flattened into a * 3 * b. Currently this is done before any other optimization and not repeated.

PERFORMANCE CONSIDERATIONS

optimize() currently takes two full loops through the AST, copying and recreating it. If you execute val() only once, calling optimize() is in fact a performance loss.

If the expression is optimizable, and you execute it $n times, you usually have a net gain over unoptimized execution if $n > 15.

Of course that value depends on the complexity of the expression, and how well it can be reduced by the implemented optimizations.

Your best is to always benchmark what you do. Most of the time the compiled version returned by ->compiled is much faster than the optimized (and not compiled) form.