Leonid Shifrin

38,137 reputation

3102195

bio	website	mathprogramming-intro.org
	location	St. Petersburg, Russia
	age	36
visits	member for	1 year, 4 months
	seen	17 mins ago
stats	profile views	3,101

Ok, an obligatory note: opinions expressed here are mine and not those of my employer.

	38,137 reputation	bio	website	mathprogramming-intro.org	visits	member for	1 year, 4 months
3102195 badges		location	St. Petersburg, Russia		seen	17 mins ago

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May 10	revised	How can I use Mathematica's graph functions to cheat at Boggle? Fixed the performance problem, and left a notice for the reason
May 10	comment	ListPlot: Plotting large data fast Very cool and informative - big +1.
May 10	comment	How can I use Mathematica's graph functions to cheat at Boggle? @Pillsy Your assumption is probably right in general, but you did not account for the huge overhead of top-level mma. Here, I reduce it to a mimimum, and I think this is a good illustration of what immutable data structures can buy you. Both the list of already visited vertices (`vvlist` parameter of `f`), and a given (sub) tree, only contain one or just a few pointers to be copied. So, my recursive function is maximally efficient, because it copies very little. Also, I don't have to build words from letters - it is a waste for this problem, where just a single last letter is always important.
May 10	revised	How can I use Mathematica's graph functions to cheat at Boggle? Fixed the wrong function name
May 10	comment	How can I use Mathematica's graph functions to cheat at Boggle? @rcollyer Thanks for the notice. `getWords` was a previous incarnation of `getVertexSequences`. They are exactly the same, I just renamed the former to the latter. Since both were defined in the workspace, I did not notice that in my tests / benchmarks. Will edit now. As for "a little while", yes, 6s. is about right, so for a single run, my solution is not really fast. But, for many runs, this will matter less, and besides, this dictionary tree can be stored in e.g. .mx file, since it may ba also useful for other applications. We only have to build it once.
May 9	revised	How can I use Mathematica's graph functions to cheat at Boggle? Added a link, fixed a typo
May 9	answered	How can I use Mathematica's graph functions to cheat at Boggle?
May 9	comment	Problem using OptionValue with functions defined by SubValues, and the use of Options for function dispatch @rcollyer That's a good point. Care to edit my answer and include it, or do you want me to do this?
May 9	awarded	Nice Answer
May 8	comment	Are there guidelines for avoiding the unpacking of a packed array? @Yu-SungChang Thanks, I was not aware of these details. Makes perfect sense.
May 7	comment	Are there guidelines for avoiding the unpacking of a packed array? @Mr.Wizard Thanks for the upvote:). I voted for you answer too.
May 7	awarded	Nice Answer
May 7	revised	Are there guidelines for avoiding the unpacking of a packed array? corrected a typo
May 7	revised	Are there guidelines for avoiding the unpacking of a packed array? Added some suggestions
May 7	revised	Are there guidelines for avoiding the unpacking of a packed array? added 44 characters in body
May 7	answered	Are there guidelines for avoiding the unpacking of a packed array?
May 6	comment	Combining lists @rcollyer Yep, he does. Anything that uses `Apply` on packed arrays, will unpack.
May 6	comment	Combining lists @rcollyer One problem with this is that it will unpack both lists if they were packed.
May 6	comment	Why doesn't Evaluate appear to work in this RegionPlot example with MatchQ? `Evaluate` overrides only `Hold`-attributes of heads immediately enclosing it, but you have another layer here (`MatchQ`). This discussion might help.
May 6	comment	How to read data file quickly? @AlbertRetey Thanks, a very good point!