On Dec 11, 2010, at 11:23 , peter dalgaard wrote: > > On Dec 11, 2010, at 08:23 , Niels Richard Hansen wrote: > >> Dear R developers >> >> Using the 'foreach' package I encounter warnings like >> >> Warning message: >> In identical(.combine, cbind) : ignoring non-pairlist attributes >> >> Warnings appear once in a new R-session when I run a >> particular piece of code - and not again. I understand from >> the source code of 'identical' that the function checks and >> believes that .combine and cbind have non-pairlist attributes, but I >> don't understand how this can be the case >> >> I have produced the following minimal example >> >> data.frame()[rep(1,1e6), ] >> library(foreach) >> identical(foreach:::defcombine, cbind) >> >> resulting in >> >> [1] FALSE >> Warning message: >> In identical(foreach:::defcombine, cbind) : >> ignoring non-pairlist attributes >> >> The warning is not related to the foreach package it seems. I get >> the same kind of warning with e.g. >> >> identical(spatial:::trmat, cbind) >> >> in a new R-session. Many other functions I have tried do, however, >> not result in the warning. The warning depends on the supposedly completely >> unrelated data frame operation. It seems also to be related to the >> fact that the data frame is empty and I extract a large number of >> columns out of this empty data frame. I would highly appreciate help >> on this to get rid of the warning in my own package. > > Hm, I think you might have tickled a buglet here. I can debug it down to a > comparison of two CHARSXPs, both having CHARSXP attributes. I'm a getting a > little rusty on debugging at that level, but I don't think CHARSXPs are > supposed to _have_ attributes in any meaningful context, so perhaps > identical() just shouldn't check. On the other hand, it could also be the > sign of a memory overrun in the preceding memory-intensive operation. >
Robert Gentleman pointed out offlist that attributes of CHARSXP are being used for cacheing and hashing, so skipping the comparison is what makes sense. I have fixed this for R-devel now (tampering with 2.12.1 RC for this sort of reason is probably best avoided). -- Peter Dalgaard Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd....@cbs.dk Priv: pda...@gmail.com ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
