Push

A few more improvements to clojush, the version of Push3/PushGP implemented in Clojure.

20100319: - Added problem-specific-report function (to be customized per problem).
      	    This can also be a convenient place to put other stuff that you want
      	    done once per generation.
      	  - Added support for saving lists of ancestors (maternal line only)
      	    along with global parameters to turn both this and the saving
      	    of total-error histories on and off.
          - Added missing calls to "keep-number-reasonable" in numeric
      	    Push instructions. This eliminates some potential crashes from runaway
            number growth.

Several improvements have been made to clojush, the version of Push3/PushGP implemented in Clojure. The version history additions are listed below, but I can also report getting upwards of 1300% CPU utilization on a dual 4-core mac, which is very nice!

VERSION HISTORY
20100227: - First distributed version.
20100301: - Added (shutdown-agents) for proper termination.
20100306: - Added history (of total errors of ancestors) to individuals.
	  - Commented out (shutdown-agents) because it prevents multiple runs
	    in a single launch of a Clojure REPL.
20100307: - Fixed bug in history: reproductive auto-simplification added was 
            adding duplicate items.
20100314: - Added instructions: *_shove, code_extract, code_insert, 
  	    code_subst, code_contains, code_container, code_position,
	    code_discrepancy, *_rand. NOTE that the presence of *_rand
            instructions means that programs produced using the full set
            of instructions may be non-deterministic. As of this writing
            pushgp (via evaluate-individual) will evaluate an individual
            only once, so it will always have whatever fitness value it 
            had upon first testing.
	  - Added globals to support integer_rand and float_rand:
            min-random-integer, max-random-integer, min-random-float
            max-random-float.
          - Fixed bug in code_car that could produce nil.
          - Made execute-instruction safe for nil (although it shouldn't 
            arise anyway).
	  - Added stress-test for testing and debugging new Push instructions.
	    See the stress-test documentation string for details.
          - Implemented size limits on intermediate results on code stack 
            (in code_cons, code_list, code-append, code_insert, code_subst, 
            exec_s, exec_y).
	  - Fixed bug in exec_s (was always a noop previously).

A first version of Push3/PushGP in Clojure is available from http://hampshire.edu/lspector/clojush. It’s currently roughly the same stuff as was implemented in the first versions of Schush, but Clojure makes it easy to do some nice things like taking advantage of multi-core CPUs. When I run this on a 2-core machine I sometimes see CPU utilizations approaching 200% — I hope to try it on an 8-core machine soon…

Psh, the Java implementation of Push, has been updated significantly and released as Psh v0.2. The following changes were made, among many others:

• Added PshInspector, a Psh interpreter inspector that displays the Psh stacks after every step of an executed program.
• Fixed iteration instructions, which were not working properly.
• Implemented auto-simplification, both as a genetic operator and to simplify programs for reports.

Psh is now being hosted on GitHub, where you can also find a more in-depth readme:

http://github.com/jonklein/Psh

A bigger update for the new year:

http://hampshire.edu/lspector/schush.ss

The biggest additions are trivial geography (which was trivial to add 🙂 but which can make a big difference) and error scaling using one form of historically assessed hardness. Here’s the full list of new changes:

20091229: - Added scale-errors parameter to schushgp; when #t this calculates
            scaled errors via the Historically Assessed Hardness (HAH) method (in the
            "current generation / quotient" setting) and uses these scaled errors
            as the basis of selection. HAH is described in:
              Klein, J., and L. Spector. 2008. Genetic Programming with Historically
              Assessed Hardness. In Genetic Programming Theory and Practice VI, edited by
              R. L. Riolo, T. Soule, and B. Worzel, pp. 61-74. New York: Springer-Verlag.
              http://hampshire.edu/lspector/pubs/kleinspector-gptp08-preprint.pdf
            This form of HAH is similar but non-identical (for non-Boolean problems)
            to "implicit fitness sharing" as described by McKay in:
              McKay, R. I. 2001. An investigation of fitness sharing in genetic programming.
              The Australian J. of Intelligent Information Processing Systems, 7(1/2):43–51.
            Also added examples using the scale-errors parameter.
          - Added three schushgp parameters to control the number of iterations of
            automatic simplification performed at various times:
            - report-simplifications:
                the number performed for each schushgp generation report
            - final-report-simplifications:
                the number performed on successful results
            - reproduction-simplifications:
                the number performed by the simplification genetic operator
          - Fixed bug in cases for factorial example.
          - Added YANK and YANKDUP instructions for all types.
20100102: - Added trivial geography, controlled by a trivial-geography-radius parameter
            to schushgp; set this to zero (the default) for no trivial geography.
            Trivial geography is described in:
              Spector, L., and J. Klein. 2005. Trivial Geography in Genetic Programming.
              In Genetic Programming Theory and Practice III, edited by T. Yu, R.L. Riolo,
              and B. Worzel, pp. 109-124. Boston, MA: Kluwer Academic Publishers.
              http://hampshire.edu/lspector/pubs/trivial-geography-toappear.pdf
            Also added an example using trivial geography.
          - Made several minor corrections to the documentation.

A minor update, adding floating point trigonometry instructions:

http://hampshire.edu/lspector/schush.ss

20091226: - Added float.sin, float.cos, float.tan.

An updated version of Schush/SchushGP, a Scheme implementation of Push/PushGP, is now available from:

http://hampshire.edu/lspector/schush.ss

The recent changes are as follows:

20090919: - New shuffle algorithm (slightly slower but conses less, more elegant).
          - Removed number-list in favor of in-range (faster, conses less, more
            elegant, but PLT-specific).
20090920: - Added explicit copyright and GPL notice, replacing previous disclaimers.
          - Interpreter states now printed in human-friendly form by run-schush
            when called with print argument #t; based on code by Thomas Helmuth.