Re: Optimize numeric multiplication for one and two base-NBASE digit multiplicands.

On Mon, Jul 1, 2024, at 15:14, Joel Jacobson wrote:
> * 0001-Optimize-mul_var-for-var2ndigits-4.patch

Found a typo, fixed in new version.

The int128 version is still slower though,
I wonder if there is something that can be done to speed it up further.

Below is a more realistic benchmark than just microbenchmarking mul_var(),
not testing the int128 version, but the code for up to 2 NBASE-digits:

```
CREATE TABLE bench_mul_var (num1 numeric, num2 numeric);

INSERT INTO bench_mul_var (num1, num2)
SELECT random(0::numeric,1e8::numeric), random(0::numeric,1e8::numeric) FROM generate_series(1,1e8);

SELECT SUM(num1*num2) FROM bench_mul_var;
Time: 8331.953 ms (00:08.332)
Time: 7415.241 ms (00:07.415)
Time: 7298.296 ms (00:07.298)
Time: 7314.754 ms (00:07.315)
Time: 7289.560 ms (00:07.290)

SELECT SUM(numeric_mul_patched(num1,num2)) FROM bench_mul_var;
Time: 6403.426 ms (00:06.403)
Time: 6401.797 ms (00:06.402)
Time: 6366.136 ms (00:06.366)
Time: 6376.049 ms (00:06.376)
Time: 6317.282 ms (00:06.317)
``

Benchmarked on a Intel Core i9-14900K machine.

/Joel