c++ - thread not working for function with template arguments -

-

i trying implement multithreaded merge sort, attempt fails compile. here code :

template <class randomaccessiterator> void merge_sort (randomaccessiterator begin,randomaccessiterator end) {     int n = end - begin;     int n1,n2;      if (n == 1)         return;      randomaccessiterator mid = begin + (end-begin)/2;       // merge_sort (begin,mid); // ok     // merge_sort (mid,end);   // ok      thread t1 (merge_sort,begin,mid); // error     thread t2 (merge_sort,mid,end);   // error      t1.join ();     t2.join ();      n1 = mid - begin;     n2 = end - mid;      merge (begin,n1,mid,n2); }

errors messages gcc (g++ -std=c++11 merge-multithread.cpp):

merge-multithread.cpp: in instantiation of ‘void merge_sort(randomaccessiterator, randomaccessiterator) [with randomaccessiterator = int*]’: merge-multithread.cpp:76:25:   required here merge-multithread.cpp:60:33: error: no matching function call ‘std::thread::thread(<unresolved overloaded function type>, int*&, int*&)’   thread t1 (merge_sort,begin,mid);                                  ^ in file included merge-multithread.cpp:4:0: /usr/include/c++/5.2.0/thread:133:7: note: candidate: template<class _callable, class ... _args> std::thread::thread(_callable&&, _args&& ...)        thread(_callable&& __f, _args&&... __args)        ^ /usr/include/c++/5.2.0/thread:133:7: note:   template argument deduction/substitution failed: merge-multithread.cpp:60:33: note:   couldn't deduce template parameter ‘_callable’   thread t1 (merge_sort,begin,mid);                                  ^ in file included merge-multithread.cpp:4:0: /usr/include/c++/5.2.0/thread:128:5: note: candidate: std::thread::thread(std::thread&&)      thread(thread&& __t) noexcept      ^ /usr/include/c++/5.2.0/thread:128:5: note:   candidate expects 1 argument, 3 provided /usr/include/c++/5.2.0/thread:122:5: note: candidate: std::thread::thread()      thread() noexcept = default;

merge_sort function template; address of 1 of instantiated functions need specify template arguments:

thread t1 (&merge_sort<randomaccessiterator>,begin,mid); //         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^

or use static cast:

thread t1 (static_cast<void(*)(randomaccessiterator,randomaccessiterator)>(&merge_sort),begin,mid);

...or use lambda expression , let compiler automatically deduce types of arguments:

thread t1 ([begin,mid]{merge_sort(begin, mid);});

Comments

Post a Comment

Popular posts from this blog

html - Firefox flex bug applied to buttons? -

-
i'm trying apply flex button on firefox i'm having problem on chrome doesn't happens. this css: .button { display: inline-flex; align-items: center; } as can see in fiddle, "caret" word moved new line, happens if element <button> tag, <div> works expected. http://codepen.io/anon/pen/xblmgx is firefox bug or there css i'm missing? nevermind, looks "mr firefox" doesn't idea... <button> not implementable (by browsers) in pure css, bit of black box, perspective of css. means don't react in same way e.g. <div> would. this isn't specific flexbox -- e.g. don't render scrollbars if put "overflow:scroll" on button, , don't render table if put "display:table" on it. stepping further, isn't specific <button> . consider <fieldset> , <table> have special rendering behavior: data:text/html,<fieldset style="d...
Read more

html - Missing border-right in select on Firefox -

-
Image
when put select div width , padding-left, options have no border on right. more, happend if select have width 118px , parent have 15px of padding left! have idea, going on? my code: <!doctype html> <html> <head lang="en"> </head> <body> <div style="width: 1000px; padding-left: 15px;"> <select style="width: 118px;"> <option>a</option> <option>b</option> <option>c</option> </select> </div> </body> </html> and result: here plunker: click it happend on firefox on windows. tested on 40.0.2 version -webkit-box-sizing: border-box; -moz-box-sizing: border-box; -ms-box-sizing: border-box; box-sizing: border-box; source: https://stackoverflow.com/a/11390432/4431269 source of problem: https://bugzilla.mozilla.org/show_bug.cgi?id=924068 and use of google ! edit: (source of problem, explained) after rea...
Read more

python - build a suggestions list using fuzzywuzzy -

-
i building suggestion engine database. i'm using fuzzywuzzy module match user input string existing database shown below. if request.method == "get": display_dict = {} user_input = request.get["user_input"] # user input match_dict = {} food_items_obj = food_items.objects.all() # fetch objects table items in food_items_obj : match = fuzz.ratio(user_input.lower(),items.name.lower()) # try match user input existing names match_dict[match] = items.name # put 1 dictionary matched_dict = ordereddict(sorted(match_dict.items(),reverse = true)) # sort dictionary if max(matched_dict.keys()) == 100: # if exact match put in dict , return display_dict[100] = matched_dict[100] else : # if not found try best matching words.. ###########this part need help! ############# k,v in matched_dict.items(): if user_input in v : display_dict[k]...
Read more