c++ - Slow iterating over string using pointers -

-

i love see why 1 of following solution slower other. lets concider following code:

// create long string int x,y; bool b; char c[10000];  (x=0;x<10000;x++)     c[x]='a'; string s(c);

now want iterate on string , compare each character other. first solution completes task in 5 seconds:

for (y=0;y<100000;y++){ (x=0;x<10000;x++){     b = (s[x]=='a'); }}

and second in 21 seconds:

string::iterator begin = s.begin(); string::iterator end   = s.end(); string::iterator i;  (y=0;y<100000;y++){     (i=begin;i<end;i++){         b = (*i=='a'); }}

why second slower?

it having dereference pointer every time comparing iterator 'a', instead of comparing actual char value. negligible difference in cases, doing 1,000,000,000 iterations noticeable.


Popular posts from this blog

Php - Delimiter must not be alphanumeric or backslash -

-
this question has answer here: delimiter must not alphanumeric or backslash , preg_match 5 answers this question has been asked don't know how fix problem in situation. getting following php errror: php message: php warning: preg_match(): delimiter must not alphanumeric or backslash in... on line 227 line 227 following: if (preg_match($match, $_server['http_user_agent'])) and function: $oslist = array ( 'windows 3.11' => 'win16', 'windows 95' => '(windows 95)|(win95)|(windows_95)', 'windows 98' => '(windows 98)|(win98)', 'windows 2000' => '(windows nt 5.0)|(windows 2000)', 'windows xp' => '(windows nt 5.1)|(windows xp)', 'windows server 2003' => '(windows nt 5.2)', 'windows vista' => '(windows nt 6.0)', 'w...
Read more

trac - Modifying workflow to add a status and split on ticket type -

-
i hoping can me lost. need modify workflow trac if ticket type spr, gets assigned our qa, , ones allowed closing ticket. otherwise, goes test team closed. as well, need ticket status flow follows: new ticket(bug) -> assigned(dev) -> fixed(re-assigned test or spr) -> closed/re-opened currently appears ticket set closed after dev fixes issue. i not familliar trac @ , have been hammering away @ 2 days , can't seem work. incredibly appreciated! try advancedticketworkflowplugin , because able act differently based on ticket field values. relevant here: triage operation based on ticket type according wiki documentation: accept = new -> * accept.name = accept ticket workflow accept.operations = triage accept.triage_field = type accept.triage_split = defect->new_defect,enhancement->new_enhancement (see more complete example on wiki page linked above)
Read more

Delphi interface implements -

-
i expect reference counting should work on outer aggregating object in interface implementation. if can refer example: clarity in classes implementing multiple interfaces (alternative delegation): here minimal reproduction of behaviour: program so16210993; {$apptype console} type ifoo = interface procedure foo; end; tfooimpl = class(tinterfacedobject, ifoo) procedure foo; end; tcontainer = class(tinterfacedobject, ifoo) private ffoo: ifoo; public constructor create; destructor destroy; override; property foo: ifoo read ffoo implements ifoo; end; procedure tfooimpl.foo; begin writeln('tfooimpl.foo called'); end; constructor tcontainer.create; begin inherited; ffoo := tfooimpl.create; end; destructor tcontainer.destroy; begin writeln('tcontainer.destroy called');//this line never runs inherited; end; procedure main; var foo : ifoo; begin foo := tcontainer.create; foo.foo; end; begin main; readln...
Read more