Basic multithreaded program Post: 302325339

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Top Forums Programming Basic multithreaded program Post 302325339 by pludi on Sunday 14th of June 2009 04:53:23 PM

06-14-2009

Registered User

OK, from what you've posted 'till now, the basic structure would be something like this (pseudo-code)

Code:

Read numbers from file
Process them
Create output files
Create array of commands to run
Total processes=0
While there are commands left
    pop a command from the stack
    fork() a subprocess
    In the child
        system() the command
    In the parent
        Total processes++
    If total processes >= 4
        wait() until any process returns

Input isn't really a problem here, since fork()ed processes inherit the parents file descriptors. Output is, since as far as I know it's hard to return data from the child to the parent without shared memory or something similar. You could save the output to a file in each child my changing stdout just before the system().
Alternatively, you could run exec() the program yourself, to reduce the fork-rate, but I'm not sure how well this would work.
Plus, with shed_setaffinity you can set the affinity of the processes (direct it which CPU to use), but you'd have to track which CPU the last process used.

Anyone with more experience with algorithms has a better idea?

pludi

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LEARN ABOUT BSD

fork

FORK(3F)																  FORK(3F)

NAME

       fork - create a copy of this process

SYNOPSIS

       integer function fork()

DESCRIPTION

       Fork  creates  a  copy  of  the	calling  process.   The only distinction between the 2 processes is that the value returned to one of them
       (referred to as the `parent' process) will be the process id of the copy.  The copy is usually referred to as  the  `child'  process.   The
       value returned to the `child' process will be zero.

       All logical units open for writing are flushed before the fork to avoid duplication of the contents of I/O buffers in the external file(s).

       If the returned value is negative, it indicates an error and will be the negation of the system error code.  See perror(3F).

       A corresponding exec routine has not been provided because there is no satisfactory way to retain open logical units across the exec.  How-
       ever, the usual function of fork/exec can be performed using system(3F).

FILES

       /usr/lib/libU77.a

SEE ALSO

       fork(2), wait(3F), kill(3F), system(3F), perror(3F)

4.2 Berkeley Distribution					   May 27, 1986 							  FORK(3F)