[Rd] Slow down using the compiler

[luke-tierney at uiowa.edu]

This is due to a temporary change to not compile assignments, like
your loop body, that appear within an argument. This is to work around
a bug elsewhere in R that will take some time to fix. Once that fix is
available these assignments will again be compiled.

Best,

On Fri, 27 Oct 2017, Colin Gillespie wrote:

> Dear All,
>
> In R 3.4.2 (Linux), the compiler seems to have regressed:
>
> $ R --vanilla
> g = function() {
>  N = 1e7; ans = numeric(N)
>  system.time({for (j in 1:N) ans[j] = 1})
> }
> g()
> #   user  system elapsed
> # 4.272   0.000   4.272
>
> g1 = compiler::cmpfun(g)
> g1()
> #   user  system elapsed
> # 4.232   0.004   4.235
>
> Running the above code in Windows 3.3.1, g() takes the same time, but g1()
> takes around 0.5 seconds.
>
> Removing the function wrapper we have
>
> N = 1e7; ans = numeric(N)
> system.time({for (j in 1:N) ans[j] = 1})
> #   user  system elapsed
> # 0.304   0.000   0.304
> compiler::enableJIT(0)
> #[1] 3
> N = 1e7; ans = numeric(N)
> system.time({for (j in 1:N) ans[j] = 1})
> #   user  system elapsed
> # 5.448   0.000   5.446
>
> Best wishes
>
> Colin
>
> ------------------
>
>> sessionInfo()
> R version 3.4.2 (2017-09-28)
> Platform: x86_64-pc-linux-gnu (64-bit)
> Running under: Ubuntu 16.04.3 LTS
>
> Matrix products: default
> BLAS: /usr/lib/atlas-base/atlas/libblas.so.3.0
> LAPACK: /usr/lib/atlas-base/atlas/liblapack.so.3.0
>
> locale:
> [1] LC_CTYPE=en_GB.UTF-8       LC_NUMERIC=C
> [3] LC_TIME=en_GB.UTF-8        LC_COLLATE=en_GB.UTF-8
> [5] LC_MONETARY=en_GB.UTF-8    LC_MESSAGES=en_GB.UTF-8
> [7] LC_PAPER=en_GB.UTF-8       LC_NAME=C
> [9] LC_ADDRESS=C               LC_TELEPHONE=C
> [11] LC_MEASUREMENT=en_GB.UTF-8 LC_IDENTIFICATION=C
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> loaded via a namespace (and not attached):
> [1] compiler_3.4.2
>
> 	[[alternative HTML version deleted]]
>
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>

-- 
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:   luke-tierney at uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu