In my (SHELX) experience, the difference in performance between 32bit and
64bit versions running on a 64bit OS scarcely justifies distributing two
sets of binaries. The 64bit binaries are usually slightly faster (especially
the multi-CPU SHELXD). As far as I know, there are no problems running the
32bit SHELX binaries on a 64bit system (zero dependencies again!). There
is however one exception: for full-matrix SHELXL refinements with a large
number of parameters, the matrix can be too large for 32bit addressing.
George
On Thu, Sep 01, 2011 at 11:36:21AM -0700, Ethan Merritt wrote:
> On Thursday, September 01, 2011 11:02:50 am Ed Pozharski wrote:
> > I am almost sure this has been addressed before, so you can go after me
> > for insufficient googling. However,
> >
> > 1. Is there any *significant* advantage in using 64-bit CCP4 binaries
> > (primarily speed)?
> > 2. IIUC, the standard CCP4 download results in 32-bit binaries being
> > run on a 64-bit system. Works for me (except for the weird iMosflm
> > issue), but given that 64-bit OS is becoming more and more common, isn't
> > it time for 64-bit binaries option? The answer, of course, is no if you
> > answered no to 1 above.
>
> The generic answer is that there is no intrinsic speed advantage to running
> a 64-bit binary rather than a 32-bit binary. In fact it may run slower
> due to larger pointer sizes and hence poorer cache performance.
> However, 32-bit binaries cannot access more than 4GB of address space.
>
> But the x64 architecture provides more registers and faster instructions
> than x86. So a 32-bit binary using the x64 instruction set can run faster
> than a 32-bit binary using only x86 instructions. Therefore you need to
> choose the right compiler options in order to get the benefit of the faster
> architecture.
>
> I do not know if there are specific CCP4 programs that fall outside of
> the generic case described above.
>
> Ethan
>
> --
> Ethan A Merritt
> Biomolecular Structure Center, K-428 Health Sciences Bldg
> University of Washington, Seattle 98195-7742
>
--
Prof. George M. Sheldrick FRS
Dept. Structural Chemistry,
University of Goettingen,
Tammannstr. 4,
D37077 Goettingen, Germany
Tel. +49-551-39-3021 or -3068
Fax. +49-551-39-22582
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