performance - Primitive types slower than user types in C++? -

-

i curious , did little benchmark determine performance delta between primitive types such int or float , user types.

i created template class var, created inline arithmetic operators. test consisted of looping loop both primitive , var vectors:

for (unsigned = 0; < 1000; ++i) {     in1[i] = i;     in2[i] = -i;     out[i] = (i % 2) ? in1[i] + in2[i] : in2[i] - in1[i]; }

i quite surprised results, turns out var class faster of time, int on average loop took 5700 nsec less class. out of 3000 runs, int faster 11 times vs. var faster 2989 times. similar results float, var 15100 nsec faster floatin 2991 of runs.

shouldn't primitive types faster?

edit: compiler rather ancient mingw 4.4.0, build options defaults of qtcreator, no optimizations:

qmake call: qmake.exe c:\...\untitled15.pro -r -spec win32-g++ "config+=release"

ok, posting full source, platform 64 bit win7, 4 gb ddr2-800, core2duo@3ghz

#include <qtextstream> #include <qvector> #include <qelapsedtimer>  template<typename t> class var{ public:     var() {}     var(t val) : var(val) {}      inline t operator+(var& other)     {         return var + other.value();     }      inline t operator-(var& other)     {         return var - other.value();     }      inline t operator+(t& other)     {         return var + other;     }      inline t operator-(t& other)     {         return var - other;     }      inline void operator=(t& other)     {         var = other;     }      inline t& value()     {         return var;     }  private:     t var; };  int main() {     qtextstream cout(stdout);     qelapsedtimer timer;      unsigned count = 1000000;      qvector<double> pin1(count), pin2(count), pout(count);     qvector<var<double> > vin1(count), vin2(count), vout(count);      unsigned t1, t2, pacc = 0, vacc = 0, repeat = 10, pcount = 0, vcount = 0, ecount = 0;     (int cc = 0; cc < 5; ++cc)     {         (unsigned c = 0; c < repeat; ++c)         {             timer.restart();             (unsigned = 0; < count; ++i)             {                 pin1[i] = i;                 pin2[i] = -i;                 pout[i] = (i % 2) ? pin1[i] + pin2[i] : pin2[i] - pin1[i];             }             t1 = timer.nsecselapsed();             cout << t1 << endl;              timer.restart();             (unsigned = 0; < count; ++i)             {                 vin1[i] = i;                 vin2[i] = -i;                 vout[i] = (i % 2) ? vin1[i] + vin2[i] : vin2[i] - vin1[i];             }             t2 = timer.nsecselapsed();             cout << t2 << endl;;             pacc += t1;             vacc += t2;         }          pacc /= repeat;         vacc /= repeat;         if (pacc < vacc) {             cout << "primitive faster" << endl;             pcount++;         }         else if (pacc > vacc) {             cout << "var faster" << endl;             vcount++;         }         else {             cout << "amazingly, both equally fast" << endl;             ecount++;         }          cout << "average primitive type " << pacc << ", average var " << vacc << endl;      }     cout << "int faster " << pcount << " times, var faster " << vcount << " times, equal " << ecount << " times, " << pcount + vcount + ecount << " times ran total" << endl; }

relatively, floats var class 6-7% faster floats, ints 3%.

i ran test vector length of 10 000 000 instead of original 1000 , results still consistent , in favor of class.

with qvector replaced std::vector, @ -o2 optimization level, code generated gcc 2 types same, instruction instruction.

without replacement, generated code different, that's hardly surprising, considering qtvector implemented differently primitive , non-primitive types (look qtypeinfo<t>::iscomplex in qvector.h).

update looks iscomplex not affect linner oop, i.e. measured part. loop code still differs 2 types, albeit slightly. looks difference due gcc.


Comments

Post a Comment

Popular posts from this blog

django - How can I change user group without delete record -

-
on website user have 1 group. , user can change group. it's made user.groups.clear() and user.groups.add(new_group) but it's not efficient, because there 2 sql query: delete, insert. how can change group update query? user , group related each other using manytomanyfield . means intersection table exists relating both entities, , if don't specify model map (using through attribute) django creates 1 you. looking @ sources django.contrib.auth.models see that's case. fortunatly, can access intermediary model using through attribute of manager (in case, user.groups.through ). can use regular model. example: >>> alice = user.objects.create_user('alice', 'alice@example.com', 'alicepw') >>> employee = group.objects.create(name='employee') >>> manager = group.objects.create(name='manager') >>> alice.groups.add(employee) >>> alice.groups.all() [<group: employee...
Read more

java - Need to add SOAP security token -

-
i need set custom soap header attribute on jax-ws generated webservice client. case webservice calls must go through proxy server requiring specific token (recieved web request header) present in soap request header. e.g.: 1 carserviceservice service = null; 2 service = new carserviceservice(new url(url), new qname(qname); 3 carserviceendpoint port = service.getcarserviceport(); it seems in line 3 wsdl retrieved , call fails due missing security token. 1 point direction on how done? a detailed example has been mentioned here: creating , deploying jax-ws web service on tomcat 6 this article shows how create , use security token .
Read more

java - EclipseLink JPA Object is not a known entity type -

-
i have strange problem eclipselink , object want persist. have 1 object (keypointlistimpl) stores object keypointimpl in list. persisting keypointimpl objects works great if try persist keypointlistimpl object java.lang.illegalargumentexception says object keypointimpl isn't known entity type. here keypointimpl code: @entity @table(name="keypoints") public class keypointimpl implements keypoint { @id @generatedvalue(strategy = generationtype.identity) private int id; @enumerated(enumtype.string) private detectortype keypointtype; private float x; private float y; private float size; private float angle; private float response; private int octave; private int classid; ... } here keypointlistimpl code: @entity @table(name="keypointlists") public class keypointlistimpl implements keypointlist { @id @generatedvalue(strategy = generationtype.identity) private int id; @onetoone(cascade={ca...
Read more