[Wien] Machines

[Peter Blaha]

These times look very unrealistic. Maybe it is because of the use of the
PRECOMPILED executables ?
In any case, I would definitely go for a new and modern machine like a
new P4. Maybe you get the best price/performance ratio by not buying the
fastest machine, but 10% slower (3.2 or 3.4 GHz).

I would buy single cpu machines.


>    I have some money to buy good machine or few P4 boxes to make a small
> cluster. With my colleagues I was able to try a Xeon (3.0GHz) with two
> processors with HT (Hyper Threathing), a P4 (2.8GHz) with one processor with
> HT and some not so new P3 (1.3GHz), these last in a cluster and each machine
> with two processors.
>    I did a test in these machines, I loaded the latest WIEN2k with the
> PRECOMPILED programs and ran a simple system with many k-points, the results
> were quite interesting;
> -------------------------------------------------------------------
> -1-, -2-, etc. refers to the number of lines in the '.machines'
> -------------------------------------------------------------------
>    In the P3 at 1.3GHz
> times:
> 
> --1--
> lapw1: 92:14
> lapw2: 11:14
> 
> --2-- one machine
> lapw1: 74:14
> lapw2:  6:20
> 
> --3-- one machine
> lapw1: 73:26
> lapw2:  6:29
> 
> --2-- two machines
> lapw1: 66:26
> lapw2:  5:48
> 
> relative times between:
> 
> -- 1 and 2 -- one machine
> lapw1: 1.78
> lapw2: 1.77
> 
> 
> -- 1 and 2 -- two machines
> lapw1: 1.98
> lapw2: 2.01
> 
> ------------------------------
> P4 at 2.8 GHz
> 
> times:
> 
> --1--
> lapw1: 71:36
> lapw2:  6:32
> 
> --2--
> lapw1: 59:29
> lapw2:  5:57
> 
> --3--
> lapw1: 57:57
> lapw2:  5:49
> 
> 
> relative times between:
> 
> -- 1 and 2 --
> lapw1: 1.20
> lapw2: 1.10
> 
> ------------------------------------
> Xeon at 3.0GHz
> times:
> 
> --1--
> lapw1: 86:52
> lapw2:  7:48
> 
> --2--
> lapw1: 55:50
> lapw2:  5:36
> 
> --4--
> lapw1: 41:21
> lapw2:  7:48
> 
> --6--
> lapw1: 39:35
> lapw2:  3:52
> 
> relative times between:
> 
> -- 1 and 2 --
> lapw1: 1.56
> lapw2: 1.39
> 
> -- 2 and 4 --
> lapw1: 1.35
> lapw2: 1.45
> 
> ------------------------------------
> The results show that;
> The Xeon is slower than the P4, and the not so new P3 are relatively faster
> than P4.
> The parallelism in the Xeon is not so good
> The HT (Hyper threading) does not duplicate the processor, that is, it does
> not work as two processors.
> The performance in the P3 is better when the load is distributed in two
> different machines compared to the case when it is calculated with the two
> processors in the same machine.
> -----------------------------------
> So my questions are:
>    If I compile the programs would I get a better relative speed?
>    What is better, one good machine or several cheaper P4?
>    Dual or single processors?
> 
>       Yours
> 
>             Pablo de la Mora
> 
> 


                                      P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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