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 > >