[Rd] Fw: Calling a LAPACK subroutine from R

[Serguei Sokol]

On 12/09/2019 11:07, Berend Hasselman wrote:
>> On 12 Sep 2019, at 10:36, Serguei Sokol<sokol using insa-toulouse.fr>  wrote:
>>
>> On 11/09/2019 21:38, Berend Hasselman wrote:
>>> The Lapack library is loaded automatically by R itself when it needs it  for doing some calculation.
>>> You can force it to do that with a (dummy) solve for example.
>>> Put this at start of your script:
>>>
>>> <code>
>>> # dummy code to get LAPACK library loaded
>>> X1 <- diag(2,2)
>>> x1 <- rep(2,2)
>>> # X1;x1
>>> z <- solve(X1,x1)
>>> </code>
>> another way is to use directly dyn.load():
>>
>> lapack.path <- paste0(file.path(R.home(), ifelse(.Platform$OS.type == "windows",
>>           file.path("bin", .Platform$r_arch, "Rlapack"), file.path("lib", "libRlapack"))),
>>           .Platform$dynlib.ext)
>> dyn.load(lapack.path)
> This will not work on macOS.
> The extension for dynamic libraries is .dylib.
> So you would need
>
> lapack.path <- paste0(file.path(R.home(), ifelse(.Platform$OS.type == "windows",
>           file.path("bin", .Platform$r_arch, "Rlapack"), file.path("lib", "libRlapack"))),
>           ".dylib")
>
> See the help for .Platform and dyn.load for the details for macOS.
Indeed. I was surprised to discover that .Platform$dynlib.ext is set to 
".so" on macos,
not to ".dylib". Thank you to point me to a special note about it in 
?.Platform
Is there a R predefined variable set to ".dylib" on macos ?
Meanwhile, the code for lapack path detection will become a little bit 
more complicated:

dynlib.ext=ifelse(Sys.info()[["sysname"]] == "Darwin", ".dylib", 
.Platform$dynlib.ext)
lapack.path <- paste0(file.path(R.home(), ifelse(.Platform$OS.type == 
"windows",
          file.path("bin", .Platform$r_arch, "Rlapack"), 
file.path("lib", "libRlapack"))),
          dynlib.ext)
dyn.load(lapack.path)
is.loaded("dgemv") # must be TRUE

Serguei.