From Niels.R.Hansen+lists at math.ku.dk  Fri Nov 19 21:28:03 2010
From: Niels.R.Hansen+lists at math.ku.dk (Niels Richard Hansen)
Date: Fri, 19 Nov 2010 12:28:03 -0800
Subject: [Rd] Error from sparse pattern matrix product
Message-ID: <4CE6DDD3.7000608@math.ku.dk>

Hi

The following attempt to minimize memory consumption fails.

m1 <- Matrix(c(rep(1,1000), rep(0,2000)), 1500)
m2 <- as(m1, "ngCMatrix")

Then

m1 %*% c(1,2)

produces the desired matrix product, while

m2 %*% c(1,2)

results in the error

Error in x %*% y :
   Cholmod error 'invalid xtype' at file:../MatrixOps/cholmod_sdmult.c, line 82

I might be making a wrong assumption that this should work, or another mistake, 
but the error is somewhat cryptic, and reading the help pages and listing the
methods for %*% indicate that matrix products with x of class ngCMatrix
should work. Anyway

object.size(m1)/object.size(m2)

indicates that in this case there is a 2.7-fold gain in memory consumption by
storing only the pattern in the ngCMatrix. This could potentially be quite
useful for large model matrices.

Sincerely, Niels

sessionInfo:

R version 2.12.0 (2010-10-15)
Platform: i386-apple-darwin9.8.0/i386 (32-bit)

locale:
[1] C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] Matrix_0.999375-45 lattice_0.19-13

loaded via a namespace (and not attached):
[1] grid_2.12.0

-- 
Niels Richard Hansen                     Web:   www.math.ku.dk/~richard	
Associate Professor                      Email: Niels.R.Hansen at math.ku.dk
Department of Mathematical Sciences             nielsrichardhansen at gmail.com
University of Copenhagen                 Skype: nielsrichardhansen.dk	
Universitetsparken 5                     Phone: +1 510 502 8161	
2100 Copenhagen ?
Denmark



[Rd] Error from sparse pattern matrix product
Niels Richard Hansen