Re: [fpc-devel] PShortString
Op Fri, 10 Sep 2010, schreef Hans-Peter Diettrich: Sergei Gorelkin schrieb: When dynamic strings are used all around, is the use of pointers to ShortString still recommended? (fmodule contains a lot of them) Whenever you care about performance, you'll quickly realize that dynamic strings are plain inappropriate. The concrete use of PShortString strings is inappropriate in your sense, because it results in allocation, copy and deallocation of temporary strings in the code, in many places. This behaviour gave birth to my question. Ansistrings result allocation copy and deallocation during *processing*. The use of ansistrings would make the compiler at least twice as slow and quadruple its memory consumption. Daniël___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] PShortString
Am 10.09.2010 02:41, schrieb Hans-Peter Diettrich: Florian Klaempfl schrieb: 1. Ancient code, keep in mind, most code not being back end code was written ~10 years ago. At this time we even could not depend on perfectly working ansistrings. I'm talking about nowadays situation. You asked for reasons why it is done as it is done. 2. Ansistring create an explicit exception frame etc. which slows down things. Also when the strings are const parameters, as they are in this case? If there is no other use, no. But if there is any processing or just a local ansistring: yes. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] PShortString
Daniël Mantione пишет: Op Fri, 10 Sep 2010, schreef Hans-Peter Diettrich: Sergei Gorelkin schrieb: When dynamic strings are used all around, is the use of pointers to ShortString still recommended? (fmodule contains a lot of them) Whenever you care about performance, you'll quickly realize that dynamic strings are plain inappropriate. The concrete use of PShortString strings is inappropriate in your sense, because it results in allocation, copy and deallocation of temporary strings in the code, in many places. This behaviour gave birth to my question. Ansistrings result allocation copy and deallocation during *processing*. The use of ansistrings would make the compiler at least twice as slow and quadruple its memory consumption. Also, don't forget that an AnsiString assignment, even when it doen not end up in memory allocations, will execute two intelocked instructions in multithreaded process. Regards, Sergei ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
[fpc-devel] PShortString
When dynamic strings are used all around, is the use of pointers to ShortString still recommended? (fmodule contains a lot of them) In many cases (almost all I found) the strings are duplicated when assigned, because the given dynamic strings disallow to simply copy the reference. IMO P[Short]Strings only were useful when the referenced string shall be changed later, with that change reflected automatically in all references. Since this seems not to occur anywhere, I'd suggest to replace or retype PShortString by [Ansi]String. DoDi ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] PShortString
Am 09.09.2010 15:52, schrieb Hans-Peter Diettrich: When dynamic strings are used all around, is the use of pointers to ShortString still recommended? (fmodule contains a lot of them) 1. Ancient code, keep in mind, most code not being back end code was written ~10 years ago. At this time we even could not depend on perfectly working ansistrings. 2. Ansistring create an explicit exception frame etc. which slows down things. Due to the explicit exception frame generation, I would propose not to change it but only if the length limitation is a problem. In many cases (almost all I found) the strings are duplicated when assigned, because the given dynamic strings disallow to simply copy the reference. IMO P[Short]Strings only were useful when the referenced string shall be changed later, with that change reflected automatically in all references. Since this seems not to occur anywhere, I'd suggest to replace or retype PShortString by [Ansi]String. DoDi ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] PShortString
Hans-Peter Diettrich wrote: When dynamic strings are used all around, is the use of pointers to ShortString still recommended? (fmodule contains a lot of them) Whenever you care about performance, you'll quickly realize that dynamic strings are plain inappropriate. When it is also known that 255 character limit won't be exceeded, ShortString is nearly an ideal choice. In many cases (almost all I found) the strings are duplicated when assigned, because the given dynamic strings disallow to simply copy the reference. IMO P[Short]Strings only were useful when the referenced string shall be changed later, with that change reflected automatically in all references. Since this seems not to occur anywhere, I'd suggest to replace or retype PShortString by [Ansi]String. They provide fine-grained control over memory allocations, avoiding implicit try..finally blocks and memory allocations for temps. Copying still occurs, but with the highly optimized Move procedure it is pretty cheap. So please don't change such things just because something is used all around. Regards, Sergei ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] PShortString
Sergei Gorelkin schrieb: When dynamic strings are used all around, is the use of pointers to ShortString still recommended? (fmodule contains a lot of them) Whenever you care about performance, you'll quickly realize that dynamic strings are plain inappropriate. The concrete use of PShortString strings is inappropriate in your sense, because it results in allocation, copy and deallocation of temporary strings in the code, in many places. This behaviour gave birth to my question. They provide fine-grained control over memory allocations, avoiding implicit try..finally blocks and memory allocations for temps. Copying still occurs, but with the highly optimized Move procedure it is pretty cheap. So please don't change such things just because something is used all around. All that would no more be needed after a decent redesign. Or the existing code is inappropriate, and all the mentioned operations can be removed from the source code, without affecting the behaviour and result. DoDi ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] PShortString
Florian Klaempfl schrieb: 1. Ancient code, keep in mind, most code not being back end code was written ~10 years ago. At this time we even could not depend on perfectly working ansistrings. I'm talking about nowadays situation. 2. Ansistring create an explicit exception frame etc. which slows down things. Also when the strings are const parameters, as they are in this case? DoDi ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
