Hey Jolyon,
I was also under the impression it was a double int. I am damn sure it was documented like this for Pascal 5.5. Even if I can find it now, it doesn't matter since I think we have proved that Delphi uses the IEEE std :) Cheers, Pieter On 18/08/2014 08:47, Jolyon Smith wrote: > @Cameron, you appear to be confused. > > Yes, Delphi uses a standard implementation of single and double types - the > IEEE standards. But I don't know where you got the idea that this standard > involves a naive pairing of two ints (of any size). Floating point types are > FAR more complex than that. e.g. the internal representation of the value "1" > in Double is not (0x00000001).(0x00000000) but (0x3fff0000).(0x00000000) > > How would I describe it otherwise ? Why, the same way that IEEE 754 describes > it of course. ;) > > http://en.wikipedia.org/wiki/Double-precision_floating-point_format [2] > > Single is similarly not a naive pairing of two int16's. In fact, the closest > I can even think that Delphi has to such a limited implementation for decimal > values is the Curreny type, but even that isn't a "pair of integers", rather > a straightforward "fixed point" with a scalar of 10,000, yielding 4 fixed > decimal places. > > Back to the OP... > > If you are using Delphi 7 and were thinking of using Single precision, then I > strongly recommend that you do some tests with some representative sample > data to establish the most efficient approach, but as a rule of thumb I would > expect to find that Single precision would be more efficient than Double (and > in the older.Win32 compilers I wouldn't be surprised if these had an even > greater performance advantage over Int64). The question then is whether > Single precision is adequate for your needs or if you need the additional > capacity of Double. > > If you are inclined toward Int64 for some reason, be aware that there was a > bug in the Delphi Int64 arithmetic in older Delphi versions. The 32-bit > compiler doesn't use hardware op-codes for Int64 operations but emulates > these in software, which is why Int64 performs less well than Double: > > I'm fairly sure this is the case even today (hence the comparative > performance of Double and Int64 even in the XE4 32-bit compiler), but > absolutely certain that it is the case with the older Delphi compilers. > > The details of the bug escape my memory right now, other than that it was a > basic arithmetic error in the compiler emitted code (and something of an edge > case), rather than a bug in an RTL function. i.e. not something that can be > easily avoided. > > But I am sure your tests will show that Single or Double are more efficient > anyway. > > On 17 August 2014 20:09, Cameron Hart <[email protected]> wrote: > > I'm confused now as I'm pretty sure Delphi uses a standard format to > represent float (the same format used anywhere else for that matter). In > which case a float is essentially two int32 (or other int's depending on the > scale of the float). Ie a single used two int16. > > One int represented the mantissa the other the exponent (in essence the > decimal portion). Together they resulted in the floating point value. > > How would you describe this otherwise? > > FROM: [email protected] > [mailto:[email protected]] ON BEHALF OF Jolyon Smith > SENT: Sunday, 17 August 2014 12:54 p.m. > > TO: NZ Borland Developers Group - Delphi List > SUBJECT: Re: [DUG] Int64 or floating point faster? > > That's curious. Who are "they" ? It doesn't sound like any floating point > implementation I ever came across in Delphi (or anywhere else, for that > matter). O.o > > On 17 August 2014 12:28, Pieter De Wit <[email protected]> wrote: > > Hi Jolyon, > >>From memory, they used 2 int32's to make a float - this could have been >>int16's - memory is very vague on this :) The one was used to represent the >>whole numbers and the other was to show the decimal numbers > > Cheers, > > Pieter > > On 17/08/2014 12:05, Jolyon Smith wrote: > > @Pieter - I don't understand what you mean when you say that "float was > int32.int32". For starters, "float" is an imprecise term. If you mean > "single" then the entire value was always 32 bit in it's entirety. If you > mean double then it was always 64 bit. What is this "in32.int32" type of > which you speak ? O.o > > On 17 August 2014 11:52, Jolyon Smith <[email protected]> wrote: > > I think there are too many variables involved to give an answer to this > question without some of those variables being reduced to known values. > > e.g. what hardware ? what version of Delphi ? x64 target or x86 ? what > precision of floating point ? > > Having said that, in a quick test knocked up in my Smoketest framework I > found that Double comfortably outperforms Int64 when compiling for Win32 but > that both Double and Int64 demonstrated improved performance when compiling > for Win64 and that whilst Double still showed some advantage it was not as > significant (and in some test runs the difference was negligible). > > If you are targeting FireMonkey you will have to bear in mind that the > back-end compiler is different to the x86/x64 backend, so results obtained > using the WinXX compilers will not necessarily be indicative of performance > on the ARM or LLVM platforms. > > Conditions: > > - Delphi XE4 > > - Running in a 64-bit Win 7 VM > > - No testing was done for correctness of the results. > > On 16 August 2014 15:30, Ross Levis <[email protected]> wrote: > > Would I be correct that int64 multiplications would be faster than floating > point in Delphi? My app needs to do several million. > > _______________________________________________ > NZ Borland Developers Group - Delphi mailing list > Post: [email protected] > Admin: http://delphi.org.nz/mailman/listinfo/delphi [1] > Unsubscribe: send an email to [email protected] with > Subject: unsubscribe > > _______________________________________________ > > NZ Borland Developers Group - Delphi mailing list > > Post: [email protected] > > Admin: http://delphi.org.nz/mailman/listinfo/delphi [1] > > Unsubscribe: send an email to [email protected] with > Subject: unsubscribe _______________________________________________ NZ Borland Developers Group - Delphi mailing list Post: [email protected] Admin: http://delphi.org.nz/mailman/listinfo/delphi [1] Unsubscribe: send an email to [email protected] with Subject: unsubscribe _______________________________________________ NZ Borland Developers Group - Delphi mailing list Post: [email protected] Admin: http://delphi.org.nz/mailman/listinfo/delphi [1] Unsubscribe: send an email to [email protected] with Subject: unsubscribe _______________________________________________ NZ Borland Developers Group - Delphi mailing list Post: [email protected] Admin: http://delphi.org.nz/mailman/listinfo/delphi [1] Unsubscribe: send an email to [email protected] with Subject: unsubscribe Links: ------ [1] http://delphi.org.nz/mailman/listinfo/delphi [2] http://en.wikipedia.org/wiki/Double-precision_floating-point_format
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