c++ - Will std::cout affect timers? -


i have graphics program, , want measure time function calls take. since not sure how std::cout works under hood, wanted ask if calls in between timer calls affect performance. know it's slow in naturally not put in functions i'm measuring, buffered/asynchronous effect linger after call returns in way? looking (pseudocode):

timer->start(); runsomefunction(); timer->stop(); std::cout << timer << std::endl; // affect next timer event? timer->start(); runanotherfunction(); timer->stop(); std::cout << timer << std::endl; // etc

in short, no.

longer answer: however, depend, cout going to, , system running on.

typically, internals of cout use sort of "write file" system call, file "standard out" filehandle - may sort of display device, window or file if output redirected. may of course lead sort of interrupt or process elsewhere running (e.g. "cmd.exe" in windows or "xterm" or similar in linux/unix). if functions short, sort of "interference" may sufficient alter results - of course, it's equally possible web-browser waking check if facebook has new items, or email software, or network other system has similar effect. however, in modern system decent multi-core processor (as long system isn't running 100% cpu usage), these effects should small , not account - whether talking cout or of other potential factors.

edit: additionally, sensitive code, effect of calling cout (or other function more couple of lines long [or loops around reading large lumps of memory, if few lines]) affect cache-content, may affect execution of code.


Comments

Post a Comment

Popular posts from this blog

linux - xterm copying to CLIPBOARD using copy-selection causes automatic updating of CLIPBOARD upon mouse selection -

i've tried various ways coerce xterm (versions 285 , 292) copy selection clipboard clipboard whenever press ctrl-shift-c. promising way far has been, in ~/.xresources, put this: xterm*vt100.translations: #override \ ctrl shift <keypress> c: copy-selection(clipboard) \n\ ctrl shift <keypress> v: insert-selection(clipboard) ctrl-shift-v works perfectly, copying has nuance... if restart xterm, highlighting text puts things in primary clipboard; expected, proper, default behavior. if hit ctrl-shift-c, copies current selection clipboard clipboard. the bug, however, if highlight text after first time pressed ctrl-shift-c, you'll see highlighting copies both primary and clipboard. cannot figure out how stop xterm updating clipboard upon selection... , doesn't make sense me in first place. i said, @ specific point in time, copy selection clipboard... yet starts updating automatically upon selection after doing once... anyone have workaround...
Read more

c++ - qgraphicsview horizontal scrolling always has a vertical delta -

Image
i've subclassed qgraphicsview custom canvas used in cad application. i've reimplemented qgraphicsview::wheelevent check keyboard modifiers control key and, if control key pressed, zoom. i'm trying implement horizontal scroll when user holds shift , uses wheel. the problem i'm having horizontal scrolling always scrolls 0.279. not huge problem, hugely annoying , points else being wrong. so, here questions: is right way implement horizontal scrolling? if not, is? how eliminate delta of 0.279? thanks in advance. code , sample output below void myview::zoom(int delta) { double factor = pow(1.2, delta/abs(delta)); this->scale(factor, factor); } void myview::scrollhorizontal(int level) { qpointf center = maptoscene(viewport()->rect().center()); qdebug() << "center: " << center.x() << ", " << center.y(); centeron(qpointf(center.x() - level, center.y())); } void myview::wheelevent(qwheeleve...
Read more