On Thu, Dec 8, 2022 at 2:53 PM Paul Ramsey <pram...@cleverelephant.ca>
wrote:
>
> random_normal(stddev float8 DEFAULT 1.0, mean float8 DEFAULT 0.0)
>
Any particular justification for placing stddev before mean? A brief
survey seems to indicate other libraries, as well as (at least for me)
learned convention, has the mean be supplied first, then the standard
deviation. The implementation/commentary seems to use that convention as
well.
Some suggestions:
/* Apply optional user parameters */ - that isn't important or even what is
happening though, and the body of the function shouldn't care about the
source of the values for the variables it uses.
Instead:
/* Transform the normal standard variable (z) using the target normal
distribution parameters */
Personally I'd probably make that even more explicit:
+ float8 z
...
* z = pg_prng_double_normal(&drandom_seed)
+ /* ... */
* result = (stddev * z) + mean
And a possible micro-optimization...
+ bool rescale = true
+ if (PG_NARGS() = 0)
+ rescale = false
...
+ if (rescale)
... result = (stddev * z) + mean
+ else
+ result = z
David J.
