CmdStanR: how to set C++ flags?

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1

I would like my models to be compiled with -march=native etc. Is there a straightforward way of setting C++ flags for the compile() method? I looked at cpp_options but I can’t figure out how to use it to pass this kind of information.

2

I think you just supply them as a string in a cpp_options list element named cxxflags:

mod$compile(
	quiet = F #to print the compile command
	, force = T #in case it was compiled before without the cpp_options
	, cpp_options = list(
		cxxflags = "-march=native"
	)
)

I haven’t done this before myself, so report back on whether I’m correct and it works for you.

3

Unfortunately, it doesn’t seem to work.

4

Ok, I have figured out how to do it. One needs to store the compiler flags in the CmdStan makefile (!!) and then rebuild the stan libraries. A bit complicated, but seems to work.

Basically something like this:

cpp_options <- list(
   "CXXFLAGS+= -O3 -march=native -mtune=native"
 )
cmdstan_make_local(cpp_options = cpp_options)
rebuild_cmdstan()
1 Like
6

What is the output you get?

7

Output in which case? Modifying the makefile as I mention in the previous post works — and it has to be done anyway, since linked stan libraries must be build with the same flags anyway.

8

Ah, sorry, the app I’m using didn’t show all of your posts, just the one saying it didn’t work.