Displaying 2 results from an estimated 2 matches for "500x20".
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500,20
2008 Feb 29
0
Variable modified from within a function
...he thing is that passing "data" as an argument to g() involves copying
the data, if I understood correctly. Something I'd be keen to avoid
because in the real programme I want to write, g() is called many a time
and data is rather big (not infamously massive, though, something like a
500x20 matrix). If no other solution exists, I can do this:
f <- function (...) {
data <- my.readfile(...);
g <- function (...) {
# Do something with data
}
g(...)
}
This may be very common practice in R, I don't know, but my feeling as a
beginner is that it's rather ineleg...
2011 Jul 19
1
Measuring and comparing .C and .Call overhead
...l works by passing pointers. (How can we explain the
slight increase in overhead?)
2- C++ times for .C are somewhat better than .Call. This is likely to be due
to the overhead associated with unpacking the SEXP pointers in a .Call
function.
3- The overhead for .C dominates the execution time. For a 500x20 matrix,
the overhead is ~90% of total time. This means that whenever we need to make
repeated calls to a C/C++ function from R, and when performance is important
to us, .Call is much preferred to .C, even at modest data sizes.
4- Overhead for .C scales sub-linearly with data size. I imagine that th...