Michel Talon wrote: > Rahul Siddharthan wrote: > > Where is the generalisation? I said "my own code", which is what I'm > > interested in. But it also appears to be true of GSL (the GNU > > scientific library), at least the parts that I'm interested in. I > > don't think, even if my claim was made "generally", it would be at all > > controversial. Floating-point performance is much better in 64-bit > > mode, and there are twice as many general-purpose registers available. > > I can confirm what Rahul is saying, perhaps this is no suprise since we are > both theoretical physicists. I see 64 bits machines being *twice* faster > than 32 bits machines (same machine, one in 32 bits Linux, the other in > 64 bits Linux) on my computations, and particularly in symbolic maths > computations, e.g. running maple 32 bits and maple 64 bits, or floating > points computations. With this experience, i don't give any credence to the > computer people who pretend that there is no difference between the two > modes, or that you need >4 Gigs memory to see the difference. Our machines > have 2 Gigs and i see an enormous difference.
I'm not a theoretical physicist, but I can confirm what you are saying. :-) On certain algorithms amd64 machines are considerably faster than i386 machines. For example I have written a small Sudoku solver which is significantly faster when compiled and run on an amd64 machine. I also believe that it's because of the greater number of CPU registers available in "long mode" of amd64 processors. (The machine in question only has 1 GB of RAM, and the Sudoku processes have a virtual size of only a few MB even, so the 4GB limit is completely irrelevant here.) It is also a popular fallacy that you need > 4 GB of RAM to be able to use the larger address space of a 64bit machine. That's wrong. The virtual address space of a process is limited by the width of a pointer (which is 32 bit in i386 mode and 64 bit in amd64 mode), not by the amount of RAM. You can have processes that are 8 GB in size on a machine with 2 GB of RAM. Only in 64bit mode, of course. Having said that, I appreciate all the work that Matt and the others are doing. But there's only a limited number of things you can work on with a (relatively) small team, compared to the other BSDs. Frankly, I'm astonished how much has been achieved in DF. Matt has done a tremendous amount of work. I'm sure that DF will grow amd64 support sooner or later, it's probably not very difficult but just requires a certain amount of time and effort. In fact it would be a pity if Matt wasted his time on it. Just my 2 cents. :-) Best regards Oliver PS: I would really love to help DF myself, but my spare time is extremely limited since I left university and went into the "real business life" ... And even worse since I got married. :) -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd Any opinions expressed in this message may be personal to the author and may not necessarily reflect the opinions of secnetix in any way.