On Tue, Oct 13, 2015 at 12:32 AM, Junio C Hamano <gitster@xxxxxxxxx> wrote:
> Stefan Beller <sbeller@xxxxxxxxxx> writes:
>
>>> The parallel_process API could learn a new "verbose" feature that it
>>> by itself shows some messages like
>>>
>>> "processing the 'frotz' job with N tasks"
>>> "M tasks finished (N still running)"
>>
>> I know what to fill in for M and N, 'frotz' is a bit unclear to me.
>
> At least I don't know what M and N should be, and I'm curious how
> you'll define them. See below.
I presumed the second school of thought. Another alternative there would
be to have 3 numbers:
"M tasks finished (N still running, K pending output)"
>
>>> in the output stream from strategic places. For example, the first
>>> message will come at the end of pp_init(), and the second message
>>> will be appended at the end of buffered output of a task that has
>>> just been finished. Once you have something like that, you could
>>> check for them in a test in t/.
>>>
>>> Just a thought.
>>
>> I like that thought. :)
>
>
> A few more random thoughts:
>
> * The only thing you could rely on if you were to use the above in
> your tests is the one from pp_init() that declares how many
> processes the machinery is going to use. M/N will be unstable,
> depending on the scheduling order (e.g. the foreground process
> may take a lot of time to finish, while many other processes
> finish first).
>
> * Every time the foreground process (i.e. the one whose output is
> tee-ed to the overall output from the machinery) finishes, you
> can emit "M tasks finished (N still running)", but I am not sure
> what M should be. It is debatable how to account for background
> processes that have already completed but whose output haven't
> been shown.
Assuming we go with your second school of thought (N are the real
running processes, M including the finished but still pending output tasks),
we may have confusing output, as the output order may confuse the
reader:
N=8 M=13 (output from live task)
...
N=8 M=12 (output from buffered task)
...
Anyone who has no knowledge of the internals, wonders why
M goes *down* ?
>
> One school of thought that is in line with the "pretend as if the
> background tasks are started immediately after the foreground
> task finishes, and they run at infinite speed and produce output
> in no time" idea, on which the "queue output from the background
> processes and emit at once in order to avoid intermixing" design
> was based on, would be not to include them in M (i.e. finished
> ones), because their output haven't been emitted and we are
> pretending that they haven't even been started. If you take this
> approach, you however may have to include them in N (i.e. still
> running), but that would likely bump N beyond the maximum number
> of simultaneous processes.
>
> The other school of thought would of course tell the truth and
> include the number of finished background processes in M, as they
> have finished already in the reality. This will not risk showing
> N that is beyond the maximum, but your first "progress" output
> might say "3 tasks finished", which will make it look odd in a
> different way.
>
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