AMBER Archive (2005)

Subject: RE: AMBER: Build for single precision

From: Ross Walker (ross_at_rosswalker.co.uk)
Date: Thu Dec 15 2005 - 10:29:35 CST

Dear David,

> I want to build amber8 to use single and not double
> precision? What do I change in the build process to get the
> preprocessor to set _REAL_ to REAL*4.

Assuming you are refering to Sander then yes this should potentially work.
Although you may have to also search for any statements along the lines of:

implicit double precision (...)

Be aware though that building single precision is not advised, you will not
maintain enough accuracy in the calculations to get useful MD results. Some
codes such as Gromacs use single precision in places to speed up the
calculation but only in specific parts of the code. Essentially it is
believed, although I have never seen this sufficiently proven to satisfy me,
that as long as you do all of the individual pairwise interactions and bond,
angle and dihedral terms in double precision you can get away with just
summing the forces in single precision.

Anyway feel free to try building a single precision executable but be aware
that the results are not likely to be usable...

All the best
Ross

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|\oss Walker

| Department of Molecular Biology TPC15 |
| The Scripps Research Institute |
| Tel: +1 858 784 8889 | EMail:- ross_at_rosswalker.co.uk |
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