python - Why are Pickle files in Pickle protocol 4 twice as large as those in protocol 3 without having any gains in speed? -

-

i testing python 3.4, , noticed pickle module has new protocol. therefore, benchmark 2 protocols.

def test1():     pickle3=open("pickle3","wb")     in range(1000000):         pickle.dump(i,pickle3,3)     pickle3.close()     pickle3=open("pickle3","rb")     in range(1000000):         pickle.load(pickle3)  def test2():     pickle4=open("pickle4","wb")     in range(1000000):         pickle.dump(i, pickle4,4)     pickle3.close()     pickle4=open("pickle4","rb")     in range(1000000):         pickle.load(pickle4)

test1 mark: 2000007 function calls in 6.473 seconds

test2 mark: 2000007 function calls in 6.740 seconds

protocol 4 slower protocol 3. kind of difference can ignored. however, hard disk usage different.

pickle3 uses 7,868,672 bytes.

pickle4 uses 16,868,672 bytes.

that's no reason. continue dig out. after read pep3154, understand protocol.

for tuple(1,2,3,4,5,6,7) of protocol 3

    0: \x80 proto      3     2: (    mark     3: k        binint1    1     5: k        binint1    2     7: k        binint1    3     9: k        binint1    4    11: k        binint1    5    13: k        binint1    6    15: k        binint1    7    17: t        tuple      (mark @ 2)    18: q    binput     0    20: .    stop

for tuple(1,2,3,4,5,6,7) of protocol 4

    0: \x80 proto      4     2: \x95 frame      18    11: (    mark    12: k        binint1    1    14: k        binint1    2    16: k        binint1    3    18: k        binint1    4    20: k        binint1    5    22: k        binint1    6    24: k        binint1    7    26: t        tuple      (mark @ 11)    27: \x94 memoize    28: .    stop

the unpickler of protocol 3 cannot know length of data until reads position 17.

for protocol 4, position 2 postion 18, there heading shows length.

however, still not why pay price (almost double hard disk usage in extreme situation) speed same or potentially slower?

you pickling ints. there no gain in knowing size of structure in advance such simple datatype. more complex structures, knowing frame size huge gain in processing speed. besides, protocol 4 lifts many restrictions 64bit systems.


Comments

Post a Comment

Popular posts from this blog

C# random value from dictionary and tuple -

-
i have following code, , need random item contains string "region_1" dictionary. public static dictionary<int, tuple<string, int, currencytype>> itemarray = new dictionary<int, tuple<string, int, currencytype>>() { { 0xb3e, new tuple<string, int, currencytype>("region_1", 1500, currencytype.fame) } }; public static int generateitemid(string shopid) { var generateditem = itemarray.elementat(new random().next(0, itemarray.count)).key; } how select this? it's not possible efficiently... first create static random @ class level... prevent non-random behaviour if run query on short period of time... (it's seeded discrete clock) static random rnd = new random(); then: var item = itemarray.values .where(t => t.item1 == shopid) .orderby(_ => rnd.next()) .firstordefault()
Read more

cgi - How do I interpret URLs without extension as files rather than missing directories in nginx? -

-
so i'm trying install zoneminder , have run under nginx, has few compiled files need run using fast-cgi. these files lack extension. if file has extension, there no issue , nginx interprets file , return 404 if can't find it. if has no extension, assume it's directory , return 404 when can't find sort of index page. here have now: # security camera domain. server { listen 888; server_name mydomain.com; root /srv/http/zm; # enable php support. include php.conf; location / { index index.html index.htm index.php; } # enable cgi support. location ~ ^/cgi-bin/(.+)$ { alias /srv/cgi-bin/zm/; fastcgi_pass unix:/run/fcgiwrap.sock; fastcgi_param script_filename $document_root/$1; include fastcgi.conf; } } the idea is, under cgi-bin directory goes through fastcgi pipe. any idea on howi can fix this? upon closer inspection, realized zoneminder has 2 cgi sc...
Read more

.htaccess - htaccess convert request to clean url and add slash at the end of the url -

-
ok , searched more 4 days , more 20 posts here in stach or in websites without kind of success first here htaccess file rewriteengine on rewriterule ^([a-za-z0-9_]+)/?$ index.php?page=$1 [nc] rewriterule ^([a-za-z0-9_]+)\/([a-za-z0-9_]+)\/?$ index.php?page=$1&action=$2 [nc] i tried many codes 1 worked me can call request , works me www.example.com/pagename => www.example.com/index.php?page=pagename here questions , please provide me information "in detail" understand code well 1- how convert request automatically www.example.com/index.php?page=pagename www.example.com/pagename 2- if tried add slash @ end shows me page without images or styling mean www.example.com/pagename => works www.example.com/pagename/ => doesn't work that's :) for first part need 301 rule this: rewritecond %{the_request} /index\.php\?page=([^\s&]+) [nc] rewriterule ^ /%1? [r=301,l] for second part use absolute path in css, js, images files r...
Read more