Hey @alalek, I do not have the environments of the failing builds, any idea how to solve? I'll fix Android now

In org.opencv.test.core.CoreTest.testGetNumberOfCPUUs(CoreTest.java:637) this line:

I'm not sure if it is true.

[EDIT]
I added a check for this

Checks pass now, open to suggestions.

Thank you for contribution!

Could you please squash commits and rebase onto 3.4 branch?

Thanks @alalek, done.

@mshabunin, I have combined some of the android and linux code to reduce duplicates, I have also fixed the logic of cpus-sets by reusing android code.

Looks like this approach not work with --cpus Docker option, because it does not change cpuset-cpus. As I understand K8S mainly use this option to limit cpu load.

Perhaps we need to handle this case too by dividing cfs_quota to cfs_period and rounding the value, because this parameter supports fractional numbers.

$ docker run --cpus 2 -it ubuntu:18.04
# cat /sys/fs/cgroup/cpu/cpu.cfs_period_us 
100000
# cat /sys/fs/cgroup/cpu/cpu.cfs_quota_us 
200000

$ docker run --cpus 1.3 -it ubuntu:18.04
# cat /sys/fs/cgroup/cpu/cpu.cfs_period_us
100000
# cat /sys/fs/cgroup/cpu/cpu.cfs_quota_us
130000

Oh, thanks @mshabunin for finding this, I'll read up on this and get back to you

@mshabunin, I've handled --cpus case. I tested it on docker and a k8s pod as well.

Thanks for the review @mshabunin, I'll address them. As for priority, I think we can take minimum most value if we have many options as that is always the most probable value.

@ganesh-k13 , yes minimum should be good. Maybe something like this will be more clear (variables and functions should have meaningful names ofc):

int result = 0;

#if CV_HAVE_METHOD_1
static const int m1 = getCPUS_method1();
if (result > 0 && m1 > 0 && result > m1 || result == 0 && m1 > 0)
    result = m1;
#endif

#if CV_HAVE_METHOD_2
...
#endif

return result > 0 ? result : 1;

Yes, that is much clearer @mshabunin, I'll do like that. Thanks.

Ok so Andriod is just hard when it comes to sched_getaffinity, seems like it's not directly supported due to missing cpu_set_t. Any pointers on how to proceed and should we even include this in Andriod code path? Open to other review comments as well. @alalek.

@ganesh-k13 I propose to preserve original implementation for Andoird and do not use cgroups option there.

Sure @asmorkalov, will do.

@alalek / @asmorkalov / @mshabunin , can you please review?

@alalek and @asmorkalov, I have made some changes. Open to any changes, this was just my first thoughts on handling Linux and Andriod based stuff. Let me know what needs to be done.