> Since the author no longer has the /proc/cpuinfo, I cannot say anything for sure. If the "fma4" flag was still there, it's a VM misconfiguration. If not, the software was only looking for the model number and not the flags, which is arguably a bug.
I touched on this in the article. I don't think Linux actually shows an fma4 CPU flag (it didn't on that VM), but a test program said it didn't support fma4. The OpenBLAS developers don't seem interested in fixing it [0], since it's unlikely to happen outside of misconfigured VMs.
My suspicion is that the server actually had an EPYC CPU, but the hypervisor was configured to say Opteron.
I touched on this in the article. I don't think Linux actually shows an fma4 CPU flag (it didn't on that VM), but a test program said it didn't support fma4. The OpenBLAS developers don't seem interested in fixing it [0], since it's unlikely to happen outside of misconfigured VMs.
My suspicion is that the server actually had an EPYC CPU, but the hypervisor was configured to say Opteron.
[0]: https://github.com/xianyi/OpenBLAS/issues/3638