[Python-Dev] Python 3.4, marshal dumps slower (version 3 protocol) (original) (raw)

Kristján Valur Jónsson kristjan at ccpgames.com
Tue Jan 28 06:14:52 CET 2014

Hi there. I think you should modify your program to marshal (and load) a compiled module. This is where the optimizations in versions 3 and 4 become important. K

-----Original Message----- From: Python-Dev [mailto:python-dev-_ _bounces+kristjan=ccpgames.com at python.org] On Behalf Of Victor Stinner Sent: Monday, January 27, 2014 23:35 To: Wolfgang Cc: Python-Dev Subject: Re: [Python-Dev] Python 3.4, marshal dumps slower (version 3 protocol)

Hi, I'm surprised: marshal.dumps() doesn't raise an error if you pass an invalid version. In fact, Python 3.3 only supports versions 0, 1 and 2. If you pass 3, it will use the version 2. (Same apply for version 99.) Python 3.4 has two new versions: 3 and 4. The version 3 "shares common object references", the version 4 adds short tuples and short strings (produce smaller files). It would be nice to document the differences between marshal versions. And what do you think of raising an error if the version is unknown in marshal.dumps()? I modified your benchmark to test also loads() and run the benchmark 10 times. Results: --- Python 3.3.3+ (3.3:50aa9e3ab9a4, Jan 27 2014, 16:11:26) [GCC 4.8.2 20131212 (Red Hat 4.8.2-7)] on linux dumps v0: 391.9 ms data size v0: 45582.9 kB loads v0: 616.2 ms dumps v1: 384.3 ms data size v1: 45582.9 kB loads v1: 594.0 ms dumps v2: 153.1 ms data size v2: 41395.4 kB loads v2: 549.6 ms dumps v3: 152.1 ms data size v3: 41395.4 kB loads v3: 535.9 ms dumps v4: 152.3 ms data size v4: 41395.4 kB loads v4: 549.7 ms --- And: --- Python 3.4.0b3+ (default:dbad4564cd12, Jan 27 2014, 16:09:40) [GCC 4.8.2 20131212 (Red Hat 4.8.2-7)] on linux dumps v0: 389.4 ms data size v0: 45582.9 kB loads v0: 564.8 ms dumps v1: 390.2 ms data size v1: 45582.9 kB loads v1: 545.6 ms dumps v2: 165.5 ms data size v2: 41395.4 kB loads v2: 470.9 ms dumps v3: 425.6 ms data size v3: 41395.4 kB loads v3: 528.2 ms dumps v4: 369.2 ms data size v4: 37000.9 kB loads v4: 550.2 ms --- Version 2 is the fastest in Python 3.3 and 3.4, but version 4 with Python 3.4 produces the smallest file. Victor 2014-01-27 Wolfgang <tds333 at gmail.com>: > Hi, > > I tested the latest beta from 3.4 (b3) and noticed there is a new > marshal protocol version 3. > The documentation is a little silent about the new features, not going > into detail. > > I've run a performance test with the new protocol version and noticed > the new version is two times slower in serialization than version 2. I > tested it with a simple value tuple in a list (500000 elements). > Nothing special. (happens only if the tuple contains also a tuple) > > Copy of the test code: > > > from time import time > from marshal import dumps > > def genData(amount=500000): > for i in range(amount): > yield (i, i+2, i*2, (i+1,i+4,i,4), "my string template %s" % i, > 1.01*i, > True) > > data = list(genData()) > print(len(data)) > t0 = time() > result = dumps(data, 2) > t1 = time() > print("duration p2: %f" % (t1-t0)) > t0 = time() > result = dumps(data, 3) > t1 = time() > print("duration p3: %f" % (t1-t0)) > > > > Is the overhead for the recursion detection so high ? > > Note this happens only if there is a tuple in the tuple of the datalist. > > > Regards, > > Wolfgang > > _> ________________________ > Python-Dev mailing list > Python-Dev at python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python- dev/victor.stinner%40gm > ail.com >

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