Re: how to refrain only use certain number of processors

[lina <lina.lastname@gmail.com>]

On Mon, Jan 30, 2012 at 10:29 PM, Jochen Spieker <ml@well-adjusted.de> wrote:
> lina:
>> On Mon, Jan 30, 2012 at 6:35 PM, Jochen Spieker <ml@well-adjusted.de> wrote:
>>> lina:
>>>>
>>>> I wished at most it only run 8 jobs simultantly, no more than 8, once
>>>> finished, a new job can continue,
>>>
>>> Xargs can be used for this. An exmaple:
>>>
>>> $ seq 1 100 | xargs -n1 -P8 echo
>>>
>>> Seq prints the numbers from 1 to 100 (one per line) and xargs starts an
>>> echo for each argument with 8 invocations in parallel.
>>
>> I don't get it well.
>
> You could help me helping you by trying to be more verbose about what
> you don't understand.
>
> But anyway, a more detailed explanation:
>
> "seq" just prints a sequence of numbers:
>
> $ seq 1 3
> 1
> 2
> 3
>
> "xargs" executes the given command (in this example a simple "echo") and
> adds arguments to this command which it reads from stdin. The --verbose
> switch makes xargs print the command before it executes it:
>
> $ echo 1 | xargs --verbose echo
> echo 1
> 1
>
> With more than one line from stdin, xargs adds as many arguments as
> possible to the command line:
>
> $ seq 1 3 | xargs --verbose echo
> echo 1 2 3
> 1 2 3
>
> Xargs -n <number> tells xargs to add only <number> of arguments to the
> command:
>
> $ seq 1 3 | xargs --verbose -n1 echo
> echo 1
> 1
> echo 2
> 2
> echo 3
> 3
>
> Xargs -P <number> tells xargs to run <number> jobs in parallel, if
> possible:
>
> $ seq 1 3 | xargs --verbose -n1 -P8 echo
> echo 1
> echo 2
> echo 3
> 1
> 3
> 2
>
> Of course, since xargs only received three lines of input, it wasn't
> able to actually run more than three jobs at once. But you can guess
> that all commands ran more or less in parallel from the fact that the
> first three lines of output are from xargs and the latter three are from
> the echo processes that xargs has launched. Incidentally, the three
> processes didn't even finish in the order they were started.
>
> Using two processes in parallel you get something like this:
>
> $ seq 1 3 | xargs --verbose -n1 -P2 echo
> echo 1
> echo 2
> 1
> echo 3
> 2
> 3
>
> In this example, xargs immediately started another job after the first
> one finished to keep running two jobs in parallel.

well, a question,

$ seq 0 3 | xargs --verbose echo A
echo A 0 1 2 3
A 0 1 2 3

How can I make the output as:

A0 A1 A2 A3

Thanks again,

P.S Very good explaination.
>
> J.
> --
> I start many things but I have yet to finish a single one.
> [Agree]   [Disagree]
>                 <http://www.slowlydownward.com/NODATA/data_enter2.html>