Re: Strange result
* Paul Brettschneider:
Hi,
Alf P. Steinbach wrote:
1. The program below should theoretically not run on my old & clunky
machine,
since theoretically it allocates 2 to 4 GB. In reality, according to
Windows
Task Manager, it allocates only some 20 MB tops. And runs fine, though
slow...
2. With MSVC, and/or with 10.000 or fewer iterations and Op vector
elements, the inefficient reference strings are faster than std::string
string, as expected. On my machine, with g++ and 100.000 iterations, the
opposite happens, and the
machine trashes on allocation and deallocation for the ref strings. I
guess on a modern machine that limit must be higher (yet another factor of
10?), but I'm interested whether (1) this can be reproduced, and (2)
whether anyone has any explanation (at a guess something causes a lot of
memory to be allocated, but it doesn't show up in Task Manager).
I think you're missing copy constructors, see below:
Disclaimer: this is late for me, so thinking box not entirely sharp...
#include <boost/progress.hpp>
#include <boost/shared_ptr.hpp>
#include <iostream>
#include <ostream>
#include <vector>
#include <string>
class RefString
{
private:
boost::shared_ptr<std::string> myString;
public:
RefString( size_t n, char c )
: myString( new std::string( n, c ) )
{}
// Missing copy constructor for non-PODs:
RefString(const RefString &s)
: myString(s.myString)
{ };
RefString &operator=(const RefString &s)
{ myString = s.myString; return *this; };
Nope, these are effectively the same as those generated automatically.
};
template< class String >
struct Op_
{
String s;
std::vector<String> v;
Op_(): s( 200, ' ' ), v( 100, s ) {}
// Missing copy constructor for non-PODs:
Op_(const Op_ &o)
: s(o.s), v(o.v) { };
Op_ &operator=(const Op_ &o)
{ s = o.s; v = o.v; return *this; };
Ditto, no need to reproduce what the language provides automatically.
Except if there's some bug in g++...
[snip]
HTH,
Paul
Well, it could have. :-) So thanks.
Cheers,
- Alf
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