Mailinglist Archive: zypp-devel (226 mails)

[Josef Reidinger <jreidinger@xxxxxxx>]

Michael Matz wrote:
> Hi,
>
> On Wed, 23 Apr 2008, josef reidiner wrote:
>
> > Interesting, I think gsub works little different so I try implement little
> > different version. Problem with replace on string with different length of
> > substitute is that each call must move some char in internall char
> > strorage...so if gsub instead of replacing append can be better
>
> This is true, but not how gsub currently is implemented.  If you do that, 
> then yes, gsub might potentially be faster.
>
> > I test it on Thursday or Friday and write here result.
>
> Cool.
>
>
> Ciao,
> Michael.

So I implement it (code of it in test file which I attach). Speed 
improve is really significant.

here is my test results:

(different size change : for ;; )
new gsub
user time: 377
system time: 2
jano replace_all
user time: 810
system time: 1


(same size change : for ;) (this quite surprise me)
new gsub
user time: 364
system time: 1
jano replace_all
user time: 530
system time: 3

(remove - change : for ;)
new gsub
user time: 368
system time: 0
jano replace_all
user time: 622
system time: 2


So what you recommend??? remove replace_all and have only new gsub or 
stay both?

welcome any comments on code
Pepa
#include <string>
#include <iostream>
#include <fstream>
#include <sys/param.h>
#include <sys/times.h>
#include <sys/types.h>
#include <boost/algorithm/string/replace.hpp>

#define LOOP 10000000

struct tms t,u;

using namespace std;

string gsub(const string& sData, const string& sFrom, const string& sTo)
{
string sNew; sNew.reserve(sData.size());
if (! sData.empty())
{
string::size_type toLen = sTo.length();
string::size_type frLen = sFrom.length();
string::size_type loc = 0;
string::size_type oldLoc = 0;
while (string::npos != (loc = sData.find(sFrom, loc)))
{
sNew.append(sData,oldLoc,loc);
sNew.append(sTo);
loc += toLen;
oldLoc = loc;
if (loc >= sNew.length())
break;
}
sNew.append(sData,oldLoc,loc);
}
return sNew;
}

string & jano_replace_all(string & str, const string & from, const string & to)
{
string::size_type pos = 0;
while((pos = str.find(from, pos)) != string::npos)
{
str.replace(pos, from.size(), to);
pos += to.size();
}
return str;
}

int main(){
  std::ofstream nul("/dev/null",ios_base::out);
  string from(":");
  string to(";;");

  cout << "new gsub" <<endl;
  times(&t);
  for (int i=0;i<LOOP;i++)
  {
    string test("test string hello world \n ::: do :::");
    nul << gsub(test,from,to);
  }
  times(&u);
  cout << "user time: " << u.tms_utime-t.tms_utime << endl;
  cout << "system time: " << u.tms_stime-t.tms_stime << endl;

  cout << "jano replace_all" <<endl;
  times(&t);
  for (int i=0;i<LOOP;i++)
  {
    string test("test string hello world \n ::: do :::");
    nul << jano_replace_all(test,from,to);
  }
  times(&u);
  cout << "user time: " << u.tms_utime-t.tms_utime << endl;
  cout << "system time: " << u.tms_stime-t.tms_stime << endl;
  
  return 0;
}