Cannot set --affinity option for 32+ CPUs

[JEduCB]

I am trying to use --affinity parameter to run System.Net.Security microbenchmarks. It works fine for <32 CPUs but when I try
--platform x64 --affinity 4294967295 (0xFFFFFFFF) to set the affinity to 32 CPUs I get this error:

MicroBenchmarks 1.0.0-dev
© Microsoft Corporation. All rights reserved.

ERROR(S):
  Option 'affinity' is defined with a bad format.
USAGE:
...

I am assuming even I am setting --platform x64, the MicroBenchmarks app is running as AnyCPU or x86 platform, and that is why I am getting the error.

Any ideas on how to fix this?

Additional info:

$ lscpu
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
Address sizes:                   52 bits physical, 57 bits virtual
CPU(s):                          56
On-line CPU(s) list:             0-55
Thread(s) per core:              1
Core(s) per socket:              56
Socket(s):                       1
NUMA node(s):                    1
Vendor ID:                       GenuineIntel
CPU family:                      6
Model:                           143
Model name:                      Intel(R) Xeon(R) Platinum 8480+
...

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.6 LTS
Release:        20.04
Codename:       focal

[huoyaoyuan]

BenchmarkDotNet parses --affinity as Int32:

https://github.com/dotnet/BenchmarkDotNet/blob/063d2f0dda0e3a1e0655de666d988d1b76304be4/src/BenchmarkDotNet/ConsoleArguments/CommandLineOptions.cs#L69

It should be fixed at their side.

[huoyaoyuan]

According to dotnet/BenchmarkDotNet#2211 , it has been fixed for >32 cores. Not sure what's happening here.