# [gameprogrammer] Re: Let's play... Name That Algorithm! :)

*From*: "Mike Gillissie" <Niyoto@xxxxxxxxxx>*To*: <gameprogrammer@xxxxxxxxxxxxx>*Date*: Sat, 5 Sep 2009 05:31:12 -0400

`FYI: Kevin's solution (or rather, his second-most-recent solution) ran in
``1.46 seconds on my dev box. Processing all combinations of a >5000 x >5000
``array. And he has since multi-threaded it. I think he did alright... ;)
`

-Mike

`----- Original Message -----`

`From: "Kevin Jenkins" <gameprogrammer@xxxxxxxxxx>`

To: <gameprogrammer@xxxxxxxxxxxxx> Sent: Saturday, September 05, 2009 12:56 AM Subject: [gameprogrammer] Re: Let's play... Name That Algorithm! :)

Probably nobody cares, but I have to apologize to Mike. I wasn't able toget it under 1 second in the time I was willing to put in. This is what Iwrote in the end, which was basically a brute force approachhttp://www.rakkar.org/sourcecode/FCMSpanningCombinationSet.cppMike wanted every possible fully connected mesh that could be generatedfrom an adjacency matrix. Originally, I thought he wanted the minimumspanning set of fully connected meshes.Kevin Jenkins wrote:If you give me a file with your input set, I'll write a C function thatwill do it in less than 1 second.Mike Gillissie wrote:Hey folks,Just an unsolicited follow-up - after trying a lot of differentapproaches, I ended up sticking with the recursive model I had already,but worked in Bob's momoization concept.Warning - I might go a little long on this one, so read only if you'recurious, bored, masochistic or find humour in the way I attempt toexplain what passes for "thinking" in my world. ;)My main concern - even with mid-range input quantities (say, 3000 units)my function executes at least 10s of billions of times (I never botheredgoing long int to get an actual count). This means that everything I doin this function can have a drastic effect on performance - even usingnon-synchronized collections costs too many cycles.So, as my way of caching results, I perform a pre-check on the adjacencytable, determining which rows of bools are subsets of others (or areidentical, meaning they're compatible with the same sets of otherunits). Essentialy I determine which unit compatibility sets are subsetsof others, and store this information in an array - unit index,subset-of index, delta (number of values that are different) anddependancy.Quick note - in the following example, 1 represents an incompatibility.Thus 0 represents compatibility.1)01110 (incompatible with 2, 3, 4) 2)10011 (incompatible with 1, 4, 5) 3)10001 etc... 4)11001 5)01110In the above, I find that 1 and 5 are equal, and 3 is a subset of 4 witha delta of 1 (representing unit 2 which is compatible with 4 but notwith 3).Since 1 and 5 are identical, I need only calculate for Unit 1. I canthen take all of the resulting combinations for Unit 1 and replace the 1with a 5.Since 3 is a subset of 4, I calculate for Unit 3 first (which has LESSincompatibilities than Unit 4), and then simply perform the same "searchand replace" to create the combinations for Unit 4, only I exclude anythat contain the "Delta" element (in this case, Unit 2).The same subset approach would be done to calculate Unit 2, since Unit 3is also a subset of 2.As Bob suggests, the success of this approach depends strongly on themake up of the data itself - there are always going to be situationswhere you just don't have enough subsets to justify the overhead ofsearching for them. But in the data set I'm currently working on, myexecution time (which had previously gone from 3.6 hours to just over 1hour) dropped to 4-8 seconds. And this can surely be fine-tuned further.A further look at the problem told me that, while some compatibilitysets will just not have any subsets to exploit, I could always measurethe Similarity between two sets. In the above, Unit 1 and Unit 2 have asimilarity of 1 (representing their shared compatibility with Unit 4).So if I was to create a "virtual" compatibility set containing Unit 4,it would become a subset of both Unit 1 and Unit 2, meaning I would onlyhave to recursively calculate that combination once, and then use theabove-approach for both Units 1 and 2. The challenge here is in findingthe optimal grouping that minimizes the number of recursive callswithout overpaying in overhead cycles.It's definitely an interesting problem for me... :) -Mike--------------------- To unsubscribe go to http://gameprogrammer.com/mailinglist.html

--------------------- To unsubscribe go to http://gameprogrammer.com/mailinglist.html

**References**:**[gameprogrammer] Re: Let's play... Name That Algorithm! :)***From:*Kevin Jenkins

## Other related posts:

- » [gameprogrammer] Let's play... Name That Algorithm! :) - Mike Gillissie
- » [gameprogrammer] Let's play... Name That Algorithm! :) - Mike Gillissie
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Vince
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Alan Wolfe
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Mike Gillissie
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Kevin Jenkins
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Kevin Jenkins
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Kevin Jenkins
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - niyoto
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Bob Pendleton
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Mike Gillissie
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Bob Pendleton
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Kevin Jenkins
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Mike Gillissie
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Mike Gillissie
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Bob Pendleton
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Mike Gillissie
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Kevin Jenkins
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Mike Gillissie
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Kevin Jenkins
- » [gameprogrammer] Re: Let's play... Name That Algorithm! :) - Mike Gillissie