DasBetterR

[bachmeier]

On Friday, 7 July 2023 at 21:54:12 UTC, jmh530 wrote:

> Cool.
>
> The main thing I want to try is rstan. They have an interface 
> called cmdstan that you can call from the command line that 
> would be possible to use with D. The problem is that you have 
> to write the data to a CSV file and then read it. So it would 
> be kind of slow and I never got around to playing around with 
> it in D. With your tool as it is, I would just have to copy the 
> data in memory, which I would expect not to be as bad of an 
> overhead as IO (but again haven't gotten around to do anything 
> with it).

I just pushed an update with a minimal example of how to call 
RStan with the following workflow:

- Allocate a double[] in D and fill it with data.
- Use a custom allocator to pass a pointer to the double[] to R.
- Call RStan functions using the data.
- Pull the results into D.

Note that:

- This is the first I've used RStan. My previous (limited) usage 
of Stan was at the command line. In practice, you'd want to 
create a better interface, so that it feels like D rather than 
passing strings of code around. I'm not familiar enough with 
RStan to do that.
- The custom allocator requires leaving 80 bits immediately 
preceding the data free for R to store its metadata related to 
the vector. There's no way around that as R would not know what 
to do without the metadata.

https://github.com/bachmeil/betterr/blob/main/testing/teststan.d