Investigating a reproducibility failure

[Konrad Hinsen]

Hi everyone,

Two years ago, I published a supposedly reproducible computation,
explaining how to re-run it at any time using Guix (it's at
https://github.com/khinsen/rescience-ten-year-challenge-paper-3/). Yesterday,
I got an e-mail from someone who tried, and failed. I tried myself, and
failed as well. But I don't understand what's going on.

To see the failure, do

   guix time-machine \
    --commit=7357b3d7a52eb5db1674012c50d308d792741c48 \
    -- build openblas

The build log is attached, the first error is

   getarch_2nd.c: In function ‘main’:
   getarch_2nd.c:12:35: error: ‘SGEMM_DEFAULT_UNROLL_M’ undeclared (first use 
in this function); did you mean ‘XGEMM_DEFAULT_UNROLL_M’?
        printf("SGEMM_UNROLL_M=%d\n", SGEMM_DEFAULT_UNROLL_M);
                                      ^~~~~~~~~~~~~~~~~~~~~~
                                      XGEMM_DEFAULT_UNROLL_M

What makes this complicated is the DYNAMIC_ARCH feature of openblas that
Guix uses on X86 architectures. I don't know the details of who this
should work and why it could fail. In particular, I don't know if the
source code file getarch₂nd is supposed to be compiled at all if all
goes well.

I doubt we can do anything to fix the past, but I would like to
understand what exactly went wrong here so we can make sure we do better
in the future.

Cheers,
  Konrad.