R devel - Jul 2011 - Manipulating single-precision (float) arrays in .Call functions

I am writing a wrapper function in C++ that calls a GPU kernel. My array type
for the GPU kernel is float, so I would like my wrapper function to receive
float arrays from R. I understand that I can use 'as.single' in R to
copy a
double-precision vector from R in single-precision format while using the
'.C' interface, but is there any way to do something similar for
'.Call'?
Given that the latter passes pointers from R to C/C++, I'm guessing this may
be impossible, but I wanted to double-check. If you can suggest a solution,
a small code sample would be much appreciated.

The reason I prefer '.Call' to '.C' is because the former passes
pointers
and therefore creates less data transfer overhead as opposed to the latter
which copies data. Is this argument controversial?

-Alireza

--
View this message in context:
http://r.789695.n4.nabble.com/Manipulating-single-precision-float-arrays-in-Call-functions-tp3675684p3675684.html
Sent from the R devel mailing list archive at Nabble.com.

On 18/07/2011 11:52 AM, Alireza Mahani wrote:
> I am writing a wrapper function in C++ that calls a GPU kernel. My array
type
> for the GPU kernel is float, so I would like my wrapper function to receive
> float arrays from R. I understand that I can use 'as.single' in R
to copy a
> double-precision vector from R in single-precision format while using the
> '.C' interface, but is there any way to do something similar for
'.Call'?
> Given that the latter passes pointers from R to C/C++, I'm guessing
this may
> be impossible, but I wanted to double-check. If you can suggest a solution,
> a small code sample would be much appreciated.
>
> The reason I prefer '.Call' to '.C' is because the former
passes pointers
> and therefore creates less data transfer overhead as opposed to the latter
> which copies data. Is this argument controversial?
R has no native type holding singles.  It exports a double to a single 
vector in .C if you ask it to, but that's not available in .Call.  
You'll need to do the copying yourself.

Duncan Murdoch