[R] performance issues: gcc 2.95.3 vs. gcc 3.2.0

RenE J.V. Bertin rjvbertin at hotmail.com
Wed Oct 16 20:10:23 CEST 2002


I recently installed gcc 3.2.0 next to my old gcc 2.95.3 . I understood that this should give me some performance gain. I indeed found some, but in a few cases I actually observed a considerable loss in performance. I would be interested to learn if others have similar experiences, and what the general opinion is concerning what version (and flags) to use for R!

1) gcc 3.2.0 -O3 can be much slower than gcc 3.2.0 -O2, causing a collection of simple
tests to take over 50s instead of under 20s. This is due to -finline-functions!!

2) I have my own graphing/analysis programme that contains an expression language with a
byte compiler (i.e. the parser constructs a call graph with the callback function pointers,
memory for arguments and other relevant information). Again, I mostly find small performance
gains, but also 1 particular construct (calling a procedure via the 'call' routine) that
is almost 10x slower with gcc 3.2.0 than with gcc 2.95.3 . (I don't understand why it is so
fast with 2.95.3 but that's another issue :)). No influence of -finline-functions here.
I imagine that this could be an issue for R too!

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