Re: [Jython-users] Multithreading in Jython

[Kevin B. <kb...@ca...>]

Here's a little sample code.
---
from threading import Thread
from time import time

class Job( Thread ):
    def run( self ):
        v = 0L
        for i in xrange( 1, 200000 ):
            v = v + i
        self.value = v

def _test( n=1 ):
    jobs = []
    for i in range( n ):
        jobs.append( Job() )

    start = time()
    map( Job.start, jobs )
    map( Job.join, jobs )
    t = time() - start

    print "%d: %.3f/%.3f" % (n, t, n and t/n)
        
map( _test, range( 5 ))

---

Note that the example above doesn't get a speedup from multiple threads, even on a two CPU box. 
Of course, if your threads are blocking on a JDBC call, you'll see a speedup...  :-)

<ObDisc>
These are microbenchmarks are thus not worth the electrons it takes to view them.
</ObDisc>

Although Jython doesn't appear to have a "global interpreter lock" a la CPython, my 2-CPU NT box shows 1 CPU utilized for 1 thread, both CPUs fully utilized for two or more threads, but the times look like:

0: 0.000/0.000
1: 0.719/0.719
2: 1.656/0.828
3: 2.485/0.828
4: 3.329/0.832

So, more threads use more CPU, but are slightly slower, even on a two-CPU box.

If you just run the 'run' method of all the jobs, instead of starting a new thread for each of them, you get better times:

0: 0.000/0.000
1: 0.656/0.656
2: 1.297/0.648
3: 1.953/0.651
4: 2.594/0.648

FWIW, the numbers for CPython are much worse (thank that global interpreter lock):

0: 0.000/0.000
1: 0.703/0.703
2: 5.360/2.680
3: 10.969/3.656
4: 11.656/2.914

CPython only uses one CPU, but still incurs the overhead of thread switching - not a pretty picture.

These results were obtained on:

Jython 2.1a1 on java1.3.0 (JIT: null)
Sun JDK 1.3.0
WinNT 4.0 SP 6a
2x PIII 600

kb


R Datta wrote:
> 
> Hi all,
> 
> I am working on a program to simulate stress testing (large number of
> users) on JDBC connections. I would like to multithread the JDBC operations.
> 
> I would appreciate some input (samples, tips etc) with anyone that has
> tried multithreading within jython scripts.
> 
> Thanks
> Raj
> 
> Thanks
> Raj Datta
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