DOS ain't dead

bigint (64-bit) arithmetic (Developers)

posted by Rugxulo , Usono, 20.03.2020, 01:49

> > What are all differences between W32 and F32 versions [NDN]
>
> The F32 (FreePascal) version for example has Big Calculator which uses the
> Int64/QWord types that are missing in Virtual Pascal.

I doubt you need my help. I don't actually know the mathematical theory behind these. Still, I'll list a few things here for my own amusement.

* QMATH0.ZIP (signed 64-bit arithmetic in (16- or 32-bit) assembly for DOS)
* BIGNUM.C (from Micro-C's MC323EXA.ZIP) for 64-bit calculator in 16-bit DOS
* 32math64.txt (20 kb text, excerpted from AMD optimization manual, uses 32-bit regs for 64-bit math)

I blindly assume this has been done to death thousands of times (literally). Somebody somewhere probably has oodles of bigint routines in various HLLs languages, optimized for various cpus. Check news://comp.lang.misc for potential contributors.

Also, I do wonder how such things are verified (especially on slow/old hardware). Do they brute force it? Prove it via mathematics? Or just (slowly, partially) run a fraction daily until they double-check all their ranges output valid data? How would somebody verify correctness on an old 286/386/486?

I'm sure it's been done many times over. I just don't know the details. Probably lots of papers, books, source code. (FPU? BCD? SIMD?)

Complete thread:

• bigint (64-bit) arithmetic - Rugxulo, 20.03.2020, 01:49 (Developers)
  • bigint (64-bit) arithmetic - alexfru, 20.03.2020, 22:54
  • bigint (64-bit) arithmetic - Rugxulo, 22.03.2020, 00:20
    • bigint (64-bit) arithmetic - marcov, 22.03.2020, 20:44