Re: R-alpha: R-testers: pmin heisenbug

Ross Ihaka (ihaka@stat.auckland.ac.nz)
Tue, 1 Apr 1997 20:35:48 +1200 (NZST)


Date: Tue, 1 Apr 1997 20:35:48 +1200 (NZST)
From: Ross Ihaka <ihaka@stat.auckland.ac.nz>
Message-Id: <199704010835.UAA28919@stat1.stat.auckland.ac.nz>
To: Friedrich.Leisch@ci.tuwien.ac.at, jlindsey@luc.ac.be
Subject: Re: R-alpha: R-testers: pmin heisenbug

I must admit to being baffled by this.  When I type "R" I get

	R : Copyright 1997, Robert Gentleman and Ross Ihaka
	Version 0.50 Beta (April 1, 1997)

	R is free software and comes with ABSOLUTELY NO WARRANTY.
	You are welcome to redistribute it under certain conditions.
	Type "license()" for details.

	> gc()
	Garbage collection ...
	150427 cons cells free (75%)
	1823k bytes of heap free (93%)
	^^^^

This indicates nearly 2Mb of heap free (which is the default).

When I type "R -v10"

	R : Copyright 1997, Robert Gentleman and Ross Ihaka
	Version 0.50 Beta (April 1, 1997)

	R is free software and comes with ABSOLUTELY NO WARRANTY.
	You are welcome to redistribute it under certain conditions.
	Type "license()" for details.

	> gc()
	Garbage collection ....
	150427 cons cells free (75%)
	10110k bytes of heap free (98%)
	^^^^

This indicates nearly 10 Mb of heap free.

The number of "cons-cells" also dictates a size restriction.
There is one list element for each vector and each string and each
list element (as well as the list element itself).  If you have
very large "character" vectors, you might be hitting this limit,
but you can increase the limit for this with (for example):

	R -n300000

(The consumption of one cell per string is perhaps the major
memory problem in R - we didn't design it with large problems
in mind.  It is probably fixable, but it will mean a lot of work).

Are you seeing these kinds of values if you gc() immediately at
startup?

	Ross

PS: The random "invalid rhs" problem is almost certainly a memory
management bug.  These usually only show up when the system is
stressed, but can be very hard to track down because they are
hard to reproduce reliably.  If you find a way of consistently
reproducing it we can probably fix it pretty quickly.
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