performance - MATLAB passing by values vs by objects -


can explain why there significant time difference? 

function [] = maincalc ()  ak=am();  t1=tic; [out] = myfun (ak.aa, ak.b, ak.c, ak.d, ak.e, ak.f, ak.g, ak.h); to1end=toc(t1)  t2=tic; [out2] = myfun2 (ak); to2end=toc(t2)

the result:

to1end =    0.047520231560659 to2end =     12.490895284055467

class ( know might there no reason use class this, whole code simplification of more complex , long code, , class necessary):

classdef      properties         aa = 1;         b = 2;         c = 3;         d = 4;         e = 2.3;         f = 4.2;         g = 5.09;         h = 12.3;     end end

function myfun:

function [out] = myfun (aa, b, c, d, e, f, g, h) n = 500000; = 0; j = 0; k = 0; l = 0; s = 1:n     = aa/b + j*k - i;     j = c/d ^ 0.5 - j / i;     k = e*f + aa/3 - k/8;     l = g + exp (h) + l ^ -1; end out.i = i; out.j = j; out.k = k; out.l = l;

function myfun2:

function [out] = myfun2 ( ak ) n = 500000; = 0; j = 0; k = 0; l = 0; s = 1:n     = ak.aa/ak.b + j*k - i;     j = ak.c/ak.d ^ 0.5 - j / i;     k = ak.e*ak.f + ak.aa/3 - k/8;     l = ak.g + exp (ak.h) + l ^ -1; end out.i = i; out.j = j; out.k = k; out.l = l;

i have read somewhere explaining matlab's copy-on-write, doesn't apply here since there no changes made member of class.

================================================================================== details below line added on 8/2/2013

marcin responded has not way matlab passes parameters functions (great discovery way!), think still has it. i've made code, , time 3 approaches need access class multiple times:

function [] = maincalc3 ()  inputvar=inputclass();  to1end = 0; to2end = 0; to3end = 0; j = 100;  = 1:j;     t1=tic;     [out] = func1 (inputvar);     to1end=toc(t1) + to1end;      t2=tic;     [out2] = func2 (inputvar.s);     to2end=toc(t2) + to2end;      t3=tic;     [out3] = func3 (inputvar);     to3end=toc(t3) + to3end; end

..............................

classdef inputclass     properties         s  = 1;     end end

...............................

function f = func1 (inputvar)     f = inputvar.s; end

...............................

function f = func2 (s)     f = s; end

...............................

function [f] = func3 (inputvar)     s=inputvar.s;     f = s; end

and result:

to1end =    0.002419525505078 to2end =    0.001517134538850 to3end =    0.002353777529397

func1() , func3() takes same time, func2 takes 60% less time. doesn't mean way matlab pass parameters functions - values or objects - affect performance?

i think has not passing object value or reference function. because in loop, in myfun2() matlab needs access object , fields multiple times. that's it.

for example, if u make third function called myfun3() follows:

function [out] = myfun3 (ak) n = 500000; = 0; j = 0; k = 0; l = 0;  % following line new <----- % remove object refencese within loop , create local variables % use in loop, instead of referencing object properties time. aa = ak.aa; b = ak.b; c=ak.c; d=ak.d; e=ak.e; f=ak.f; g=ak.g; h=ak.h;  s = 1:n     = aa/b + j*k - i;     j = c/d ^ 0.5 - j / i;     k = e*f + aa/3 - k/8;     l = g + exp (h) + l ^ -1; end out.i = i; out.j = j; out.k = k; out.l = l;

the execution of function faster myfun1(). on pc resutls are:

to1end =      0.0533   to2end =     23.9410   to3end =      0.0526 % result myfun3() function

Comments

Post a Comment

Popular posts from this blog

basic authentication with http post params android -

i doing basic authentication passing username , password , using basicnamevaluepair sending post params response service. my method: public stringbuilder callservicehttppost(string username, string password, string type) { // create new httpclient , post header httpclient httpclient = new defaulthttpclient(); httppost httppost = new httppost(webservice + type); httpresponse response = null; stringbuilder total = new stringbuilder(); try { url url = new url(webservice + type); /*string base64encodedcredentials = base64.encodetostring((username + ":" + password).getbytes(), base64.url_safe | base64.no_wrap);*/ string base64encodedcredentials = "basic " + base64.encodetostring( (username + ":" + password).getbytes(), base64.no_wrap); httppost.setheader("auth...
Read more

vb.net - Virtual Keyboard commands -

i wondering difference between virtual these keyboard commands is: keyeventf_extendedkey , keyeventf_keyup is. everywhere have looked gives me description based off integers , not want know each of them does. you've tagged question vb.net, these have nothing @ vb.net. they're constants defined in windows header files, use win32 api functions. as far difference, can't tell looking @ values. individual values not particularly important, that's why named identifiers used. what's important used , documentation functions tells mean. the first one, keyeventf_extendedkey , used keybdinput structure (which used along e.g. sendinput function) pass information synthesized keyboard input. if flag used, means scan code should interpreted extended key. technically, means scan code preceded prefix byte value 224 (&he0 in hexadecimal notation). the second one, keyeventf_keyup , 1 of flags available use structure. means key being released (going up)...
Read more

How to get multiresult with multicondition in Sql Server -

i need solve this. hopefully can giving me advices. for sample, i've got data : proclib.march 1 first 10 rows flight date depart orig dest miles boarded capacity ----------------------------------------------------------------- 114 01mar94 7:10 lga lax 2475 172 210 202 01mar94 10:43 lga ord 740 151 210 219 01mar94 9:31 lga lon 3442 198 250 622 01mar94 12:19 lga fra 3857 207 250 132 01mar94 15:35 lga yyz 366 115 178 271 01mar94 13:17 lga par 3635 138 250 302 01mar94 20:22 lga 229 105 180 114 02mar94 7:10 lga lax 2475 119 210 202 02mar94 10:43 lga ord 740 120 210 219 02mar94 9:31 lga lon 344...
Read more