[R] Memory Management under Linux: Problems to allocate large amounts of data
Dubravko Dolic
Dubravko.Dolic at komdat.com
Wed Jun 29 13:26:55 CEST 2005
Dear Group
I'm still trying to bring many data into R (see older postings). After solving some troubles with the database I do most of the work in MySQL. But still I could be nice to work on some data using R. Therefore I can use a dedicated Server with Gentoo Linux as OS hosting only R. This Server is a nice machine with two CPU and 4GB RAM which should do the job:
Dual Intel XEON 3.06 GHz
4 x 1 GB RAM PC2100 CL2
HP Proliant DL380-G3
I read the R-Online help on memory issues and the article on garbage collection from the R-News 01-2001 (Luke Tierney). Also the FAQ and some newsgroup postings were very helpful on understanding memory issues using R.
Now I try to read data from a database. The data I wanted to read consists of 158902553 rows and one field (column) and is of type bigint(20) in the database. I received the message that R could not allocate the 2048000 Kb (almost 2GB) sized vector. As I have 4BG of RAM I could not imagine why this happened. In my understanding R under Linux (32bit) should be able to use the full RAM. As there is not much space used by OS and R as such ("free" shows the use of app. 670 MB after dbSendQuery and fetch) there are 3GB to be occupied by R. Is that correct?
After that I started R by setting n/vsize explicitly
R --min-vsize=10M --max-vsize=3G --min-nsize=500k --max-nsize=100M
> mem.limits()
nsize vsize
104857600 NA
and received the same message.
A garbage collection delivered the following information:
> gc()
used (Mb) gc trigger (Mb) limit (Mb) max used (Mb)
Ncells 217234 5.9 500000 13.4 2800 500000 13.4
Vcells 87472 0.7 157650064 1202.8 3072 196695437 1500.7
Now I'm at a loss. Maybe anyone could give me a hint where I should read further or which Information can take me any further
Dubravko Dolic
Statistical Analyst
Tel: +49 (0)89-55 27 44 - 4630
Fax: +49 (0)89-55 27 44 - 2463
Email: dubravko.dolic at komdat.com
Komdat GmbH
Nymphenburger Straße 86
80636 München
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