Shrinking multicore

[aviggiano]

Describe the desired feature

Currently, it seems like Echidna uses a single core/process/thread to shrink failed sequences.

In some cases, however, we're interested in using 100% of the machine's resources to extract the results of that particular sequence. For example, this is often the case when I am using stopOnFail: true and workers: N in a multicore setup. I don't care about other failed properties, I only care about that particular one that I know to have failed. The problem is that this takes forever even if I bump up N or the number of cores.

It seems like trying to shrink a sequence on a c5.large instance takes about the same amount of time as on a c5.4xlarge (benchmark pending), which is unexpected.

[ggrieco-tob]

It seems it was already reported here: #1105.. by you 😄

[aviggiano]

Haha yeah I remember that issue, but this one is different.

• [Bug-Candidate]: Echidna multicore produces slower shrinking behavior #1105 relates to how different workers result in a slower shrinking behavior than using 1 worker
• Shrinking multicore #1249 (this issue) relates to how echidna could use all cores to make shrinking run faster

For example, suppose there was a threads: 32 (or something like that); even with workers: 1, I would want echidna to use all of my 32-vCPU instance cores to make shrinking run faster