Re: Decimal: Formal review begins

From: Glen Fernandes (glen.fernandes_at_[hidden])
Date: 2025-01-20 20:28:28

On Mon, Jan 20, 2025 at 3:11 PM Matt Borland  wrote:

> On Monday, January 20th, 2025 at 12:48 PM, Glen Fernandes  wrote:
>
> > I mentioned this to Matt, but I would like to see benchmarks comparing
> > boost::decimal64_fast to a Decimal64 backed by Intel's DFP library, which
> > is what I know to be in actual use today:
> >
> https://www.intel.com/content/www/us/en/developer/articles/tool/intel-decimal-floating-point-math-library.html
> > Not that the benchmarks comparing to GCC's Decimal64 (which is based on
> the
> > libbid which ships with libgcc) aren't useful, I personally don't know
> > anyone using that today.
> >
> > Benchmarks should ideally also include Intel's compiler, because at least
> > one of the relevant parties who motivated me to suggest the Decimal64
> > library (to Vinnie as a potential project) do use the Intel C++ compiler
> > (and their Fortran compiler) for areas where they perform better.
> >
> > (The non-fast versions don't matter to me. I don't know anyone who would
> > want to use them).
>
> Here are some preliminary results:
>
> All tests run on an i9-11900k with Ubuntu 24.04 and the Intel(R) oneAPI
> DPC++/C++ Compiler 2025.0.4 (2025.0.4.20241205). The Intel benchmarks are
> written in C but should be a faithful port. Bottom line up front is the
> Intel library is an order of magnitude faster.
>

Thank you Matt.  This reconciles with what I know about everyone using the
Intel library (especially the BSL proclamation about it being 10 times
faster). These numbers should be added to the documentation.

I think there is some work to be done to make Boost.Decimal viable. i.e. We
don't want to be an order of magnitude slower than what everyone else is
actually using today.

Glen