Re: Permutations & Computer capacity
- To: mathgroup at smc.vnet.net
- Subject: [mg16939] Re: [mg16902] Permutations & Computer capacity
- From: "Mark E. Harder" <harderm at ucs.orst.edu>
- Date: Thu, 8 Apr 1999 02:32:41 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Francisco-
If there's something wrong with your computer, my computer is the same.
The problem you suggested -- creating permutations of a 12-element list--
used up all available real & virtual memory on my machine too. I am running
Mtca 3.0 on a Windows Nt 4.0 machine with 192 Mb RAM & approx 200Mb paging
file. Running your permutations on 9-element list added about 20Mb to memory
use & there are approx 3 orders of magnitude more permutations in a
12-element list. So if memory usage in computing the permutations is only
linear in the length of the list, its no wonder that we run out of memory.
I haven't tried it, but the Utilities`MemoryConserve package contains some
routines for preventing memory depletion and for compressing the storage of
symbol values. Look up "Memory Management" in the Main Index in the Find
Help menu.
-mark
-----Original Message-----
From: Francisco Gutierrez <rpena at impsat.net.co>
To: mathgroup at smc.vnet.net
Subject: [mg16939] [mg16902] Permutations & Computer capacity
>
>I developed a notebook to evaluate the Shapley value (votation power) of =
>a
>list of parties in a committee. A list to be evaluated looks like:
>{{partyA, 5}, {partyB, 8}...{partyn, X}}
>
>Everything works ok but...disgracefully producing the Shapley value impli=
>es
>working with permutations. This means making n! evaluations (n the lengt=
>h
>of the list).
>
>And when I have a list of more than 8-9 parties, the program gets stuck.
>Now, 9! is not such a big number.
>
>I thought that perhaps my programming was not efficient enough, so I made
>the following try:
>Range[12]
>Permutations[%]
>After a couple of minutes, I got the answer "Exiting-out of memory"
>I have a Pentium II with 128 RAM, 4 free gigas in hard disk and a 300 and
>something processor (my platform is windows 95).
>
>Is there something wrong with my computer? Is there a way to overcome thi=
>s
>limitation?
>
>Many thanks
>
>Francisco Gutierrez
>
>