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Dr.
Craig A. Hunter's altivec results:
| Jet3D is a jet noise prediction method. It allows us
to take a computational fluid dynamics (CFD) simulation
of a jet exhaust flow from an aircraft, and predict how
much noise it will make. This is generally targeted towards
exhaust nozzles on commercial aircraft, in the interest
of understanding and reducing community noise around airports.
As we move towards faster aircraft and more air traffic,
noise will be a bigger and bigger issue. Thus, we need
tools like Jet3D to quickly and efficiently evaluate jet
noise and design quieter aircraft. |
| Just as CFD is the computational analog to a wind tunnel
or flight test, Jet3D is the computational analog to making
microphone measurements in an acoustic jet noise lab or
making microphone measurements of a real aircraft during
a "flyby". As you can imagine, it is much faster,
safer, and cheaper to simulate this stuff on a computer
than to run an experiment or conduct a flight test. |
| Jet3D is written in standard FORTRAN 77. I ported it
over to OS X using the Absoft compiler, which has been
working great. After getting the scalar version of the
code running, I worked on the AltiVec version. I was able
to replace key computations within the code (about 10
lines of code) with subroutine calls. These subroutines
are written in C, and actually do the number crunching
with AltiVec instructions. I compiled the C subroutines
with the standard "cc" compiler that comes with
Apple's Developer Tools. I had to "backtrack"
a little to manipulate the data into vector form and pass
it to the subroutines, but the resulting performance boost
from AltiVec more than made up for the difference (I got
roughly a 9X boost in performance using AltiVec). Very
impressive. Though it took me about a week to implement
AltiVec in Jet3D, it was simpler than I thought. Next
time around, I could probably do the same amount of work
in a few hours. |
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