[Rd] serialization regression in 2.15.0 beta

[Ben Goodrich]

In case anyone is concerned that this regression will affect them, the
code was reverted to the 2.14.x behavior by

------------------------------------------------------------------------
r58842 | ripley | 2012-03-26 08:12:43 -0400 (Mon, 26 Mar 2012) | 1 line
Changed paths:
   M /branches/R-2-15-branch/doc/NEWS.Rd
   M /branches/R-2-15-branch/src/library/parallel/R/unix/forkCluster.R
   M /branches/R-2-15-branch/src/library/parallel/R/unix/mcfork.R

revert to XDR serialization for 2.15.0
------------------------------------------------------------------------

Thanks,
Ben


> I am experiencing a problem related to serialization behavior in  
> 2.15.0 beta (binary installed from Debian unstable) and 2.16.0 (from  
> svn) that is not present in 2.14.2 (binary from Debian testing).
> 
> I don't fully understand the problem. Also, I tried but have not yet  
> been able to create a small, self-contained example that reproduces  
> the problem. However, I do have a large, not self-contained example,  
> which requires an alpha version (not yet on CRAN) of the mi package  
> (the mi package on CRAN would not exhibit this issue). Anyone  
> interested in reproducing the problem can follow the readme.txt file  
> in this directory:
> 
> http://www.columbia.edu/~bg2382/mi/serialization/
> 
> I track r-devel with git-svn and was able to git bisect to svn commit r58219
> 
> commit 799102bd9d0266fe89c3120981decf0b1f17ef11
> Author: ripley <ripley at 00db46b3-68df-0310-9c12-caf00c1e9a41>
> Date:   Sat Jan 28 15:02:34 2012 +0000
> 
>      make use of non-xdr serialization;.
> 
> although this commit could merely expose the problem rather than cause it.
> 
> The problem occurs when the FUN called by mclapply() in the parallel  
> package returns a S4 object that contains a slot (called X) that is a  
> large matrix, specifically a "model matrix" similar to that produced  
> by glm(). Some columns of this matrix get corrupted with wrong values  
> (usually zero, but sometimes NaN or 10^300ish), which can be seen by  
> examining X right before FUN returns (to mclapply()'s environment) and  
> comparing to the "same" X after mclapply() returns to the calling  
> environment.
> 
> Part of svn commit r58219 is this hunk
> 
> diff --git a/src/library/parallel/R/unix/mcfork.R  
> b/src/library/parallel/R/unix/mcfork.R
> index 8e27534..4f92193 100644
> --- a/src/library/parallel/R/unix/mcfork.R
> +++ b/src/library/parallel/R/unix/mcfork.R
> @@ -82,7 +82,8 @@ mckill <- function(process, signal = 2L)
>   ## used by mcparallel, mclapply
>   sendMaster <- function(what)
>   {
> -    if (!is.raw(what)) what <- serialize(what, NULL, FALSE)
> +    # This is talking to the same machine, so no point in using xdr.
> +    if (!is.raw(what)) what <- serialize(what, NULL, xdr = FALSE)
>       .Call(C_mc_send_master, what, PACKAGE = "parallel")
>   }
> 
> Contrary to the comment, I have found that if I specify xdr = TRUE, I  
> get the expected (non-corrupted X slot) behavior in 2.16.0, even  
> though it is forking locally on my 64bit Debian laptop with a little  
> endian i7 processor, whose specs are
> 
> goodrich at CYBERPOWERPC:/tmp/serialization$ cat /proc/cpuinfo
> processor       : 0
> vendor_id       : GenuineIntel
> cpu family      : 6
> model           : 42
> model name      : Intel(R) Core(TM) i7-2630QM CPU @ 2.00GHz
> stepping        : 7
> microcode       : 0x17
> cpu MHz         : 800.000
> cache size      : 6144 KB
> physical id     : 0
> siblings        : 8
> core id         : 0
> cpu cores       : 4
> apicid          : 0
> initial apicid  : 0
> fpu             : yes
> fpu_exception   : yes
> cpuid level     : 13
> wp              : yes
> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge  
> mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe  
> syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl  
> xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl  
> vmx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt  
> tsc_deadline_timer xsave avx lahf_lm ida arat epb xsaveopt pln pts dts  
> tpr_shadow vnmi flexpriority ept vpid
> bogomips        : 3990.83
> clflush size    : 64
> cache_alignment : 64
> address sizes   : 36 bits physical, 48 bits virtual
> power management:
> 
> ...
> 
> processor       : 7
> [same as processor 0]
> 
> So, to summarize I get the good behavior on R 2.14.2 when using  
> mclapply(), on 2.15.0 beta when using lapply(), and on 2.16.0 using  
> mclapply() iff I patch in xdr = TRUE in sendMaster(). I get the bad  
> behavior on 2.15.0 beta and unpatched 2.16.0 when using mclapply().
> 
> My session info:
> 
>> sessionInfo()
> R version 2.15.0 beta (2012-03-16 r58769)
> Platform: x86_64-pc-linux-gnu (64-bit)
> 
> locale:
>   [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
>   [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
>   [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
>   [7] LC_PAPER=C                 LC_NAME=C
>   [9] LC_ADDRESS=C               LC_TELEPHONE=C
> [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
> 
> attached base packages:
> [1] stats4    stats     graphics  grDevices utils     datasets  methods
> [8] base
> 
> other attached packages:
>   [1] mi_0.9-83        bigmemory_4.2.11 arm_1.5-03       foreign_0.8-49
>   [5] abind_1.4-0      R2WinBUGS_2.1-18 coda_0.14-5      lme4_0.999375-42
>   [9] Matrix_1.0-4     lattice_0.20-0   MASS_7.3-17
> 
> loaded via a namespace (and not attached):
> [1] grid_2.15.0  nlme_3.1-103
> 
> Thanks,
> Ben