Push

Several changes have been made to Clojush, the most significant of which is the implementation of stackless tagging (motivated here and here, with the implemented details described below).

20101102: - Switched to new clojure.core/frequencies from depricated
            seq-utils/frequencies (h/t Kyle Harrington), and similarly
            for flatten.
          - Added :include-randoms keyword argument for registered-for-type.
            Defaults to true, but if specified as false then instructions
            ending with "_rand" will be excluded.
          - Raised invalid output penalty in tg8 (it was lower than reasonable
            errors for that problem).
20101103: - Converted evalpush-limit and evalpush-time-limit into vars
            (global-evalupush-limit and global-evalpush-time-limit) bound
            to atoms that are reset by calls to pushgp (keyword arguments
            :evalpush-limit and :evalpush-time-limit).
          - Changed pushgp parameters in the tg8.clj example.
20101104: - Implemented stackless tagging (see http://push.i3ci.hampshire.edu/
            2010/10/28/stackless-tagging/). Tag instructions take one of
            the following forms:
              tag_<type>_<number>
                create tage/value association, with the value taken from the
                stack of the given type and the number serving as the tag
              untag_<number>
                remove the association for the closest-matching tag
              tagged_<number>
                push the value associated with the closest-matching tag onto
                the exec stack (or no-op if no associations).
            Here "closest-matching" means the tag with lowest number that
            is greater than or equal to the number of the tag being matched,
            or the lowest-numbered tag if none meet this criterion. Tag
            instructions are not implemented in the same way as other
            instructions; they are detected and handled specially by the
            interpreter (see execute-instruction). Tag instructions
            can be included in pushgp runs by using the new ephemeral
            random constant functions tag-instruction-erc,
            untag-instruction-erc, and tagged-instruction-erc, each of
            which takes a limit (for the numerical part) as an
            argument.
          - Added examples using tags: tagged_ant, tagged_regression, and
            tagged_tg8.

This entry was posted on November 4, 2010 at 10:09 pm and is filed under Uncategorized.