gcc and alphalinux

Mathew Lee lmathew at okstate.edu
Wed May 24 15:45:44 PDT 2000

I am currently in the process of constructing a 4 node beowulf for MD
simulations.  Each node will be equiped with an Alpha 5XX (21164) and
approximately 576mb ram each.  (more nodes may be introduced if an increase in speed is needed.)

Curious about speed differences between unix and linux, I tested two
different machines with the same hardware setup.  One of the machines was
running digital's unix, and the other linux (distro=redhat 6.2).
Additionally, the kernel on the linux machine was built using only the
drivers needed.

To my surprise, the duration for all runs tested were approximately 3 times
longer on the linux machine.  Do I need to look into the use of options
with the compiler to optimize the code?  If so, where can I get a list of
what each of the options, and their meaning, (gcc and ccc).  Also, will
these same options apply when I build the code that includes the message
passing to utilze the beowulf.

Additionally, I tested the compiler made by compaq (ccc) to see if the gcc
compiler might be the problem.  Using this compiler (ccc)to build the
source with no compiler options, I again to see the speed differences.
Again, the speeds were approximately the same as the gcc compiler.  This is
unacceptable.  In fact, the four node beowulf configured this way will at
best be slightly faster than the single digital unix machines that are
currently used to run our simulations.  Any insight or suggestions as to
the source of my problem or possible solutions is gladly appreciated.

Matt Lee
Undergraduate Research Assistant
Mechanical and Aerospace Engineering
Oklahoma State University

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