On 3 January 2009 at 18:02, l...@stat.uiowa.edu wrote:
| The current byte code compiler available from my web site speeds this
| (highly artificial) example by about a factor of 4. The experimental
| byte code engine I am currently working on (and that can't yet do much
| more than an example like this) speeds this up by a factor of
| 80. Whether that level of improvement (for toy examples like this)
| will remain once the engine is more complete and whether a reasonable
| compiler can optimize down to the assembly code I used remain to be
| seen.
Stephen Milborrow's jit compiler and Ra variant -- for which the R 2.8.1
version was released today -- already delivers improvements somewhere near
the middle of 'four' to 'eighty' times:
e...@ron:~> R --slave < /tmp/ajayshah.R
user system elapsed
0.052 0.056 0.109
user system elapsed
68.984 0.088 69.384
e...@ron:~> Ra --slave < /tmp/ajayshah.Ra
user system elapsed
0.096 0.068 0.162
user system elapsed
2.06 0.10 2.16
e...@ron:~> diff -u /tmp/ajayshah.R*
--- /tmp/ajayshah.R 2009-01-03 11:05:03.000000000 -0600
+++ /tmp/ajayshah.Ra 2009-01-03 18:37:20.000000000 -0600
@@ -2,4 +2,4 @@
system.time(a <- a + 1)
-system.time(for (i in 1:10000000) {a[i] <- a[i] + 1})
+system.time({ jit(1); for (i in 1:10000000) {a[i] <- a[i] + 1} })
e...@ron:~>
The vectorised example shows highly variable times anywhere between 0.11 to
0.17 seconds so taking ratios is speculative. Either way, you can get a
speedup of maybe 30 times by switching to a just-in-time compiler for R and
adding an additional function call.
Dirk
--
Three out of two people have difficulties with fractions.
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