[Rd] From .Fortran to .Call?

[Koenker, Roger W]

Indeed, using profmem there is a significant advantage in memory:

>  sum(mb$bytes)
[1] 261834640   #using .Fortran
> sum(ma$bytes)
[1] 149221000  #using .C64

> On Dec 26, 2020, at 10:22 PM, Kasper Daniel Hansen <kasperdanielhansen using gmail.com> wrote:
> 
> Did you check memory usage? I don't know anything about Fortran, but using .Call for C code doesn't duplicate the memory of the objects you supply to the interface, and in some instances, that's an advantage. But that assumes you're doing something like
>   .Call("foo", xx)
> and not
>   Call("foo", as.matrix(xx))
> 
> 
> 
> On Sat, Dec 26, 2020 at 5:48 PM Koenker, Roger W <rkoenker using illinois.edu> wrote:
> I’ve recoded a version of one of my quantile regression fitting functions to use .C64 from dotCall64 rather than .Fortran.
> For a moderately large problem with n = 500,000 and p = 5, and solving for  1:49/50 quantiles the new version shows
> a 3% speedup, although for smaller problems it is actually slower that the .Fortran version.  So, I’m (provisionally) 
> unimpressed by the claims that .Fortran has a big “overhead” performance penalty.  Compared to the(more than) an order of
> magnitude (base 10) improvement that moving from R to fortran produces,  3% isn’t really worth the (admittedly) minimal
> additional coding effort.