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https://github.com/rofl0r/jobflow

distribute and coordinate work using parallel processes (like GNU parallel, but much faster and memory-efficient)
https://github.com/rofl0r/jobflow

c fast gnu-parallel lightweight parallel pipes process unix

Last synced: 11 days ago
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distribute and coordinate work using parallel processes (like GNU parallel, but much faster and memory-efficient)

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README 

        
jobflow by rofl0r

=================



this program is inspired by the functionality of GNU parallel, but tries

to keep low overhead and follow the UNIX philosophy of doing one thing well.



how it works

------------



basically, it works by processing stdin, launching one process per line.

the actual line can be passed to the started program as an argv.

this allows for easy parallelization of standard unix tasks.



it is possible to save the current processed line, so when the task is killed

it can be continued later.



example usage

-------------



you have a list of things, and a tool that processes a single thing.



    cat things.list | jobflow -threads=8 -exec ./mytask {}



    seq 100 | jobflow -threads=100 -exec echo {}



    cat urls.txt | jobflow -threads=32 -exec wget {}



    find . -name '*.bmp' | jobflow -threads=8 -exec bmp2jpeg {.}.bmp {.}.jpg



run jobflow without arguments to see a list of possible command line options,

and argument permutations.



starting from version 1.3.1, jobflow can also be used to extract a range of

lines, e.g.:



    seq 100 | jobflow -skip 10 -count 10  # print lines 11 to 20



Comparison with GNU parallel

----------------------------



GNU parallel is written in perl, which has the following disadvantages:

- requires a perl installation

  even though most people already have perl installed anyway, installing it

  just for this purpose requires up to 50 MB storage (and potentially up to

  several hours of time to compile it from source on slow devices)

- requires a lot of time on startup (parsing sources, etc)

- requires a lot of memory (typically between 5-60 MB)



jobflow OTOH is written in C, which has numerous advantages.

- once compiled to a tiny static binary, can be used without 3rd party stuff

- very little and constant memory usage (typically a few KB)

- no startup overhead

- much higher execution speed



apart from the chosen language and related performance differences, the

following other differences exist between GNU parallel and jobflow:



+ supports rlimits passed to started processes

- doesn't support ssh (usage of remote cpus)

- doesn't support all kinds of argument permutations:

  while GNU parallel has a rich set of options to permute the input,

  this doesn't adhere to the UNIX philosophy.

  jobflow can achieve the same result by passing the unmodified input

  to a user-created script that does the required permutations with other

  standard tools.



available command line options

------------------------------



    -skip N -threads N -resume -statefile=/tmp/state -delayedflush

    -delayedspinup N -buffered -joinoutput -limits mem=16M,cpu=10

    -eof=XXX

    -exec ./mycommand {}



-skip N



    N=number of entries to skip

-count N



    N=only process count lines (after skipping)

-threads N (alternative: -j N)



    N=number of parallel processes to spawn

-resume



    resume from last jobnumber stored in statefile

-eof XXX



    use XXX as the EOF marker on stdin

    if the marker is encountered, behave as if stdin was closed

    not compatible with pipe/bulk mode

-statefile XXX



    XXX=filename

    saves last launched jobnumber into a file

-delayedflush



    only write to statefile whenever all processes are busy,

    and at program end

-delayedspinup N



    N=maximum amount of milliseconds

    ...to wait when spinning up a fresh set of processes

    a random value between 0 and the chosen amount is used to delay initial

    spinup.

    this can be handy to circumvent an I/O lockdown because of a burst of

    activity on program startup

-buffered



    store the stdout and stderr of launched processes into a temporary file

    which will be printed after a process has finished.

    this prevents mixing up of output of different processes.

-joinoutput



    if -buffered, write both stdout and stderr into the same file.

    this saves the chronological order of the output, and the combined output

    will only be printed to stdout.

-bulk N



    do bulk copies with a buffer of N bytes. only usable in pipe mode.

    this passes (almost) the entire buffer to the next scheduled job.

    the passed buffer will be truncated to the last line break boundary,

    so jobs always get entire lines to work with.

    this option is useful when you have huge input files and relatively short

    task runtimes. by using it, syscall overhead can be reduced to a minimum.

    N must be a multiple of 4KB. the suffixes G/M/K are detected.

    actual memory allocation will be twice the amount passed.

    note that pipe buffer size is limited to 64K on linux, so anything higher

    than that probably doesn't make sense.

-limits [mem=N,cpu=N,stack=N,fsize=N,nofiles=N]



    sets the rlimit of the new created processes.

    see "man setrlimit" for an explanation. the suffixes G/M/K are detected.

-exec command with args



    everything past -exec is treated as the command to execute on each line of

    stdin received. the line can be passed as an argument using {}.

    {.} passes everything before the last dot in a line as an argument.

    it is possible to use multiple substitutions inside a single argument,

    but currently only of one type.

    if -exec is omitted, input will merely be dumped to stdout (like cat).



BUILD

-----



just run `make`.



you may override variables used in the Makefile and set optimization

CFLAGS and similar thing using a file called `config.mak`, e.g.:



    echo "CFLAGS=-O2 -g" > config.mak

    make -j2