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Groups > comp.lang.c++ > #30118
| From | Lynn McGuire <lmc@winsim.com> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: deep copy or shallow copy? |
| Date | 2014-07-26 01:37 -0500 |
| Organization | A noiseless patient Spider |
| Message-ID | <lqvidh$2kd$1@dont-email.me> (permalink) |
| References | <645bf8d9-4e56-4398-aa39-056ba5e5d434@googlegroups.com> <lqun5m$she$1@dont-email.me> <lquntl$u0$1@dont-email.me> |
On 7/25/2014 6:06 PM, Victor Bazarov wrote:
> On 7/25/2014 6:53 PM, Lynn McGuire wrote:
>> On 6/24/2014 12:53 PM, mbalover2014@gmail.com wrote:
>>> Hi all,
>>>
>>> lets assume that I have a structure defined as
>>>
>>> struct A
>>> {
>>> float arr[100];
>>> }
>>>
>>>
>>> A a1;
>>> A a2;
>>>
>>> // Initialize a1, a2.
>>>
>>> memcpy(&a1,&a2,sizeof(A));
>>>
>>> is it a deep copy or still shallow copy?
>>>
>>> Also how about a2 = a1; is it a deep copy or shallow copy from a1 to a2?
>>>
>>>
>>> Thank you.
>>
>> First, do not use structs in C++ code. Sadly, we
>> have a lot of old C code that was promoted to C++
>> by changing the .c to a .cpp so we have structs
>> all over the place.
>
> What's wrong with using 'struct'?
I prefer classes.
>> That said, the nice thing about the STL is that it
>> allows you to go shallow or deep. You can use:
>> std::vector <myClass> anObj;
>> or
>> std::vector <myClass *> anObj;
>>
>> We frequently use the pointer variant in order to
>> just make a temporary list of objects subject to
>> some criteria. Passing around pointers is a lot
>> faster and the corresponding new and delete's for
>> these objects is a very controlled situation. We
>> have very little memory leakage in our app of
>> 700K lines of C++ code.
>
> So, for the sake of some miniscule (likely guessed, not measured)
> performance gain you risk "very little memory leakage"? What's the big
> idea, a little leakage is OK, but a little time spent copying object is
> a no-no?
>
> V
Our objects can be up to a couple of hundred megabytes
in size. We do have a clone method in each class for
copying the object but copying them is a freaking
disaster for our Win32 application. Win64 is a long
way away for us.
Most of the data in our objects is text for which we
use compression for. But once uncompressed, we leave
it uncompressed until the user wants to move to a new
dataset. Too dadgum long to compress / recompress
all the time.
And funny thing is that when we moved from Win16 to
Win32, we wondered what we were going to do with all
this memory. There is never enough memory! The first
time I had a memory jump was when UCC replaced their
Univac 1108/32 with a 1108/64. I thought that 64K of
36 bit words was the cat's meow. Little did I know
that every memory jump would be followed by bigger
apps very soon after.
Lynn
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deep copy or shallow copy? mbalover2014@gmail.com - 2014-06-24 10:53 -0700
Re: deep copy or shallow copy? Robert Wessel <robertwessel2@yahoo.com> - 2014-06-24 13:01 -0500
Re: deep copy or shallow copy? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2014-06-24 20:19 +0000
Re: deep copy or shallow copy? drew@furrfu.invalid (Drew Lawson) - 2014-06-26 12:43 +0000
Re: deep copy or shallow copy? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2014-07-01 15:23 +0000
Re: deep copy or shallow copy? Victor Bazarov <v.bazarov@comcast.invalid> - 2014-06-24 16:32 -0400
Re: deep copy or shallow copy? Juha Nieminen <nospam@thanks.invalid> - 2014-06-26 04:48 +0000
Re: deep copy or shallow copy? JiiPee <no@notvalid.com> - 2014-07-18 10:37 +0100
Re: deep copy or shallow copy? CHIN Dihedral <dihedral88888@gmail.com> - 2014-07-22 13:28 -0700
Re: deep copy or shallow copy? Victor Bazarov <v.bazarov@comcast.invalid> - 2014-07-22 16:37 -0400
Re: deep copy or shallow copy? CHIN Dihedral <dihedral88888@gmail.com> - 2014-07-23 03:17 -0700
Re: deep copy or shallow copy? Victor Bazarov <v.bazarov@comcast.invalid> - 2014-07-23 08:47 -0400
Re: deep copy or shallow copy? CHIN Dihedral <dihedral88888@gmail.com> - 2014-07-23 14:14 -0700
Re: deep copy or shallow copy? Wouter van Ooijen <wouter@voti.nl> - 2014-07-23 09:28 +0200
Re: deep copy or shallow copy? Juha Nieminen <nospam@thanks.invalid> - 2014-07-24 05:21 +0000
Re: deep copy or shallow copy? CHIN Dihedral <dihedral88888@gmail.com> - 2014-07-25 08:05 -0700
Re: deep copy or shallow copy? Lynn McGuire <lmc@winsim.com> - 2014-07-25 17:53 -0500
Re: deep copy or shallow copy? Victor Bazarov <v.bazarov@comcast.invalid> - 2014-07-25 19:06 -0400
Re: deep copy or shallow copy? CHIN Dihedral <dihedral88888@gmail.com> - 2014-07-25 18:59 -0700
Re: deep copy or shallow copy? ojackson520@gmail.com - 2014-07-25 23:56 -0700
Re: deep copy or shallow copy? scott@slp53.sl.home (Scott Lurndal) - 2014-07-28 13:35 +0000
Re: deep copy or shallow copy? Lynn McGuire <lmc@winsim.com> - 2014-07-28 15:54 -0500
Re: deep copy or shallow copy? David Brown <david.brown@hesbynett.no> - 2014-07-29 12:30 +0200
Re: deep copy or shallow copy? Reinhardt Behm <rbehm@hushmail.com> - 2014-07-29 18:56 +0800
Re: deep copy or shallow copy? Tobias Müller <troplin@bluewin.ch> - 2014-07-29 12:03 +0000
Re: deep copy or shallow copy? scott@slp53.sl.home (Scott Lurndal) - 2014-07-29 14:21 +0000
Re: deep copy or shallow copy? Victor Bazarov <v.bazarov@comcast.invalid> - 2014-07-29 12:39 -0400
Re: deep copy or shallow copy? Martijn Lievaart <m@rtij.nl.invlalid> - 2014-07-29 18:48 +0200
Re: deep copy or shallow copy? Wouter van Ooijen <wouter@voti.nl> - 2014-07-29 19:16 +0200
Re: deep copy or shallow copy? Victor Bazarov <v.bazarov@comcast.invalid> - 2014-07-29 14:38 -0400
Re: deep copy or shallow copy? scott@slp53.sl.home (Scott Lurndal) - 2014-07-29 19:24 +0000
Re: deep copy or shallow copy? David Brown <david.brown@hesbynett.no> - 2014-07-30 11:08 +0200
Re: deep copy or shallow copy? Paavo Helde <myfirstname@osa.pri.ee> - 2014-07-29 15:30 -0500
Re: deep copy or shallow copy? Lynn McGuire <lmc@winsim.com> - 2014-07-26 01:37 -0500
Re: deep copy or shallow copy? Ian Collins <ian-news@hotmail.com> - 2014-07-26 20:22 +1200
Re: deep copy or shallow copy? CHIN Dihedral <dihedral88888@gmail.com> - 2014-07-26 03:19 -0700
Re: deep copy or shallow copy? Wouter van Ooijen <wouter@voti.nl> - 2014-07-26 14:34 +0200
Re: deep copy or shallow copy? Lynn McGuire <lmc@winsim.com> - 2014-07-26 16:56 -0500
Re: deep copy or shallow copy? Richard Damon <Richard@Damon-Family.org> - 2014-07-26 18:26 -0400
Re: deep copy or shallow copy? Ian Collins <ian-news@hotmail.com> - 2014-07-27 11:14 +1200
Re: deep copy or shallow copy? Victor Bazarov <v.bazarov@comcast.invalid> - 2014-07-27 10:54 -0400
Re: deep copy or shallow copy? "Osmium" <r124c4u102@comcast.net> - 2014-07-27 10:01 -0500
Re: deep copy or shallow copy? CHIN Dihedral <dihedral88888@gmail.com> - 2014-07-27 16:12 -0700
Re: deep copy or shallow copy? Victor Bazarov <v.bazarov@comcast.invalid> - 2014-07-27 14:35 -0400
Re: deep copy or shallow copy? Stuart <DerTopper@web.de> - 2014-07-28 17:24 +0200
Re: deep copy or shallow copy? Victor Bazarov <v.bazarov@comcast.invalid> - 2014-07-28 12:52 -0400
Re: deep copy or shallow copy? scott@slp53.sl.home (Scott Lurndal) - 2014-07-28 18:43 +0000
Re: deep copy or shallow copy? scott@slp53.sl.home (Scott Lurndal) - 2014-07-28 13:39 +0000
Re: deep copy or shallow copy? Victor Bazarov <v.bazarov@comcast.invalid> - 2014-07-26 11:34 -0400
Re: deep copy or shallow copy? Lynn McGuire <lmc@winsim.com> - 2014-07-26 16:59 -0500
Re: deep copy or shallow copy? scott@slp53.sl.home (Scott Lurndal) - 2014-07-28 13:32 +0000
Re: deep copy or shallow copy? Lynn McGuire <lmc@winsim.com> - 2014-07-28 14:28 -0500
Re: deep copy or shallow copy? Juha Nieminen <nospam@thanks.invalid> - 2014-08-04 05:56 +0000
Re: deep copy or shallow copy? Lynn McGuire <lmc@winsim.com> - 2014-08-05 11:41 -0500
Re: deep copy or shallow copy? Juha Nieminen <nospam@thanks.invalid> - 2014-08-07 11:03 +0000
Re: deep copy or shallow copy? Lynn McGuire <lmc@winsim.com> - 2014-08-07 12:29 -0500
Re: deep copy or shallow copy? Öö Tiib <ootiib@hot.ee> - 2014-08-04 05:02 -0700
Re: deep copy or shallow copy? Lynn McGuire <lmc@winsim.com> - 2014-08-05 11:43 -0500
Re: deep copy or shallow copy? Öö Tiib <ootiib@hot.ee> - 2014-08-05 17:13 -0700
Re: deep copy or shallow copy? Lynn McGuire <lmc@winsim.com> - 2014-08-06 15:14 -0500
Re: deep copy or shallow copy? CHIN Dihedral <dihedral88888@gmail.com> - 2014-08-20 20:56 -0700
Re: deep copy or shallow copy? Mikołaj Małecki <ethouris@gmail.com> - 2014-08-11 00:13 -0700
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