[R] R and C++ compared with only C++
Richard A. O'Keefe
ok at cs.otago.ac.nz
Tue Jul 22 05:30:30 CEST 2003
Francisco J Molina <fjmolina at lbl.gov> asked:
I have written a program in R that calls C++.
The program spends most of the time in C++ ( > 90% ). ...
How slower can this be compared with the program I would get
from rewriting everything in C++?
Suppose the program takes 1 minute in R and 9 minutes in C++.
Suppose you could make the R code *infinitely* faster by
rewriting it in C++. Then the program would just take 9 minutes in C++.
Your program would then take 90% or the time, or run 11% faster.
If course, if your rewritten R code *wasn't* infinitely fast in C++,
the gain would be even less. It could even be slower (because the
C++ code you wrote might not be as good as the C, C++, or Fortran
code that R was really spending its time in).
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