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8
Achieving a Pioneering Outlook with Supercomputing
Lawrence G. Usler
Apple Computer; Inc.
Apple purchased a Cray-XMP/48 computer a little more than 3 years
ago. It has taken a while for us to develop a range of applications. Currently
about 20 different projects are using the Cray, and they involve about 50
engineers. Most of the applications that we have are proprietary and cannot
be talked about, but fortunately there are some recent applications that I
can discuss for this symposium.
EXTENDING THE RANGE OF APPLICATIONS
lathe main reason we bought a Cray was to make applications possible
that were previously impossible because of the time they took to run. We
had circuit simulations, for example, that would have run for 2 months,
and it was easier to actually build the circuit and try it out than to wait the
2 months to run the simulation on, say, a VAX. The Cray has helped us a
lot, because now we can run those simulations in 1 day.
We had applications that would run overnight, and you had to really
plan them well, start them running, and then come back the next day to
see the results. If there was a mistake, you had to make a little change and
run the application again. Those we can now do in a few minutes, and we
can try many variations quickly, as the other speakers have mentioned.
More importantly, there were things that previously had to be done
in the batch mode that we can now do interactively, a requirement that
Beverly Eccles of Abbott Laboratories talked about very well. But the main
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91
reason we bought the Cray is that we ourselves are a computer company,
and our job is to create the computers of the future.
The group that I run, the Advanced Technology Group, is not de-
signing products for Apple. We are doing research on and prototyping of
technologies that will apply to future products. So we are looking 3, 5, or
10 years ahead for what might be applicable in future Apple products. For
us, the supercomputer is a way to experience the kinds of speed that will
be on the desktop in the $1,000 to $10,000 range in several years.
1b make that possible, we have created a somewhat unusual setup.
The network that we have at Apple includes the Cray-XMP. We recently
upgraded the disk storage on that to about 30 gigabytes. In addition
we have an EN-641 that connects us to Ethernet, and we have VAXs
and many Sun and Apollo workstations on Ethernet as gateways into the
AppleTalk network, which allows us to connect up to the many thousands
of Macintoshes that are all around the Apple campus, including more than
1000 in engineering.
On the Macintoshes we have software, for example, NCSA-TELNET,
as well as a product from Pacer software that allows us to do terminal
emulation, file transfer, and so on, by using convenient menus. We are
able to produce not only text but also graphic displays on the Macintosh to
access the power of the supercomputer.
We also have, in addition to the standard 50-megabyte hyperchannel,
an 800-megabyte-per-second ultrachannel that gives us very high bandwidth
video out, essentially, to a number of high-resolution monitors, so that
we can get direct interaction with the Cray. When we do that, we are
temporarily tying down the entire machine for one user. If someone is
rotating an image in three dimensions, the machine is dedicated as a
personal computer to that user for a few seconds while that is going on.
Some of the applications I will discuss rely on that capability.
We use the Cray both in product development and in research. We
use it for circuit design simulations, and that has saved a lot of time in
proving designs. Disk head design is an application I will discuss; industrial
design is another.
The disk head design project is an interesting one. The goal is to
make the recording head fly at a constant height over the disk surface, on
the order of 10 microinches. The shape of the head and the shape of the
medium and the aerodynamics all interact. If the system is not set up well,
then the head will crash, or the head will be too high above the disk to get
a clean signal. We wanted to know what the effects of various parameters
were.
An interesting problem we ran into was that if the head itself, the air
bearing, has a resonant frequency that corresponds to the frequency of the
rotation, oscillations result. To understand that better, we worked with Jim
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LAWRENCE G. TESLER
White from the University of Santa Clara. The disk head can have little
bevels and other shapes that affect the aerodynamics. Our engineers came
up with a set of equations based on the geometry of the head.
One of the problems is that the medium itself is not completely flat.
It can be a thousandth of an inch off flatness, and when the head is flying a
few hundred thousandths of an inch over the disk, that variation can cause
a problem because essentially, the head is like a cruise missile trying to go
over peaks.
In a simulation, the head can be shown as flying between-150 and 350
or so nanometers over the surface. By varying the shape of the head, the
engineers can run the simulation over and over. The simulation takes only
20 minutes to run, and the engineers can keep playing with it until they
achieve satisfactory results.
Another concern is that there may be a problem caused by a slight
bump in the medium. A little of the oxide may have a small bump in it,
and a result may be that the head can really bounce. And of course if it
bounces too much, it will crash.
Another area to explore is what happens if there is a jolt to the head,
which can happen because someone moves the drive while it is running.
After a seek, when the head comes to a stop, there is a similar jolt. We
need to know how long it will take the oscillation of the head to settle
down so that we can actually start to do a read or write.
Why is Apple studying all these things when in fact we do not man-
ufacture disk mechanisms? The reason is that we work with vendors of
heads and media, and vendors of drives, and they come to us with claims
of why the next generation of disks is going to be so much better than the
last. We need to be able to evaluate their claims, because if we simply go
along with them and something does not work well, then we might have to
shut down our production, and that is a serious consequence.
Product Design
We have also used the Cray for product design, or packaging. We
have used three different applications: (1) thermal analysis, (2) structural
analysis, and (3) mold flow similar to that discussed by Cliff Perry.
For thermal analysis we have used a package called ANSYS, which is
a finite element program displaying the output graphically on a Macintosh
II. For example, we have modeled a personal computer board, with major
heat sources displayed as small blue areas. A simulation is run until it
settles into a steady state, which occurs after the computer has been on for
a while. Then the task is to see what temperatures the various components
have reached.
~,
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It is possible to tune the heat flow in the system by adjusting the
cooling air how and the layout so that it is all in the range of about 143
to 152°F, but some hot spots may remain. By playing with the parameters,
engineers can try to get the temperatures within an acceptable range for
the components.
Another application, called NEKTONics, is a finite element program
that is used for structural analysis related to the cooling problem. A small
object represents the edge of a cooling vent. Just above and below that
object is a vent; a piece of plastic separates the vents. As air is drawn in
through the package, the flow is depicted. The question is, What will the
temperature be after a certain period of time, given certain assumptions
about air flow and the initial conditions?
This program can show potential problems. For example, if air flows
past a particular point and loses velocity, it also loses its ability to cool. It is
possible to play with the shape of a particular edge and solve the problem
of reduced air flow. By manipulating with a computer-aided design (CAD)
program the shape of a vent edge, a different flow pattern was obtained,
and the result was that the velocity loss was reduced.
A third application is used for a mold flow problem. What is interesting
in this example is that the product we used this application for was the
large-size, extended keyboard for the Macintosh II. A keyboard for a
Macintosh has various places on the surface that, if looked at in just the
right way, are small dark areas. These are weld lines where the plastic has
come through the mold and welded together, and they are not very good
to look at. The problem was to try to improve the keyboard's appearance
so that people would stop telephoning Customer Support to ask why they
couldn't clean their keyboards.
The approach to this problem was to break the keyboard's surface
down into very small polygons and then to run a simulation that showed
the filling of the plastic in the mold. The point at which the plastic in two
paths merges together becomes a weld line. The idea is to try to control
conditions so that the temperature of the two is about the same and the
weld occurs in a place where it will not be noticed by the user. This is the
case in the newly designed keyboard, not in our original design.
In a two-dimensional display of mold flow, different colors represent
different time periods so that it is possible to see the history of the flow.
Now there is an interactive program that shows the process in real time.
The engineer can use a mouse to select a specific part of the picture and
then can view a blown-up zoomed-in view of just that part. This gives the
engineer the ability to focus on parts of the process. Our application does
not have the aesthetics of the visualization that Cliff Perry described or the
ability to show multiple parameters at once. Instead, we traded that off to
be able to get interactive capability for the engineer.
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LAWRENCE G. TESLER
We also can do pressure and temperature plots, and so on. What
is important is that in the end, the engineer gives to the plastic maker
a drawing that shows the key things that have to be done. Basically the
approach to solving the problem of getting the plastic to flow at the rate
that we wanted was to indicate places where the inside of the mold was
narrower, which slowed down the plastic flow so that we could catch up
in other places. This approach gave the result we wanted; the weld lines
were exactly where we wanted them. The illustration was done with a
program called PIXELPAINT on the Macintosh II, by starting with the
CAD diagram and simply taking the data that came out of the simulation.
The benefits of using the supercomputer for product design are in-
creased savings of time and money hundreds of thousands of dollars-
made possible by fewer tooling runs plus the much greater advantage of
getting products to market faster. We can get products to market months
faster because we know that the likelihood that the first mold is going to
work is much higher. We also do not have to wait months for another
mold if there is something wrong with the first one, and we can improve
the various parameters of the design and get better quality.
Research
Now we also use our supercomputer in research. At Apple, we have
been doing neural network simulations to better understand how to use
different neural net models for learning. In addition, we have simulated a
cochlear model that is used in a speech recognition project. The idea is
that, to be usable, any speech recognition system has to be able to work
in a noisy room. One approach to achieving that is to try to actually
model the human ear, which has a comb of hairs that is able to sort
out different frequencies and to measure, essentially, the energy at each
different frequency.
Some work had been done at Schlumberger Research by Dick Lyon,
who recently came to Apple. What we decided to do was to take the same
type of model that he had implemented, implement it on the Cray, and
then animate the results.
The result is a plot, called a correlogram, that shows low frequencies
at the top and high frequencies at the bottom. Viewed from left to right, it
shows various correlations of different timing sets. Essentially it enables the
engineer to "see" what the ear "sees" when it hears a sound. An utterance
can be visualized as pillar-shaped forms that represent the main frequency
and as other forms that represent other, weaker frequencies. If there is
noise in the room, the background becomes fuzzy, but it is still possible to
see a pattern of frequencies standing out. This is the beginning of a very
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long research project to try to emulate the power of the human ear to sort
out noise.
For neural net simulation we have been able to get very high rates on
the Cray. Using even only one processor on the XMP, we have been able
to do about 10 million connection updates per second and also to animate
the results to get a feel for how a neural net learns.
So the benefits for research are, again, more rapid prototyping. We
can try many alternatives. People are willing to try things if they can get
results in a few minutes, or even interactively, but the main thing is that
we are now much bolder. We will try things that we would not have tried
before. One of the chips that we are designing currently is one we probably
would not have attempted to design previously because people thought it
would not work. When we simulated it, we found that it would work, and
we went ahead and built it and in fact it did work. So I would say that the
main impact of the supercomputer is that it makes us more comfortable
with taking bigger risks.
ADDING SUPERCOMPUTING CAPABILITY
Visualization, as everyone participating in this symposium has ex-
plained, is an absolutely key capability. Having a fast network is very,
very important, and we continue to upgrade the speed of our network so
that people can get higher bandwidth between the user interface and the
supercomputer. One big problem is simply operating the supercomputer
center. It accounts for a major portion of our budget, and we are always
under pressure to add new power to it. It is competing always with other
needs such as upgrading the network and adding minisupercomputers and
workstations. The operations end is something that anyone thinking of
buying a supercomputer really must consider.
Two years ago we brought in a person from our Management Infor-
mation Systems Department to manage our supercomputer center, and
we have hired several people who are expert in using the CraY and other
supercomputer engineering systems to work there.
The last hurdle, as other people have mentioned, has been to get the
users to use the supercomputer. The way we do it is that we have a small
group of people we call Cray evangelists. They do not appear on television;
they walk around. They go to engineers and try to find out what those
engineers do, and then they try to match them up with applications on the
Cray or help them write their own applications on the Cray. All of the
applications I have discussed in this symposium have come from that effort,
which is very similar to what was described as the effort that goes on at
Kodak also.
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DISCUSSION
DISCUSSION
Edward Abrahams: Have you who have tackled this problem of con-
vincing users to use the supercomputer found some techniques that were
not so productive? Presumably you have mentioned some of the ones that
are productive. What techniques did not work, so we can avoid them?
Lawrence Tesler: Trying to convince somebody who is very negative is
probably the one thing that isn't worth doing. In other words it's important
to find people who immediately see the benefits of supercomputing and to
get them to start using it. Then their colleagues will realize that they can
use supercomputing also.
Beverly Eccles: Yes. Seek the champions for the cause.
Clifford Perry: I don't have too many keys to failure, but one key
to success is involving the users from the very beginning in participative
planning. We actually sent out letters to literally hundreds of the heavy
users of our traditional high-end mainframe computing facility, asking them
to participate in an idealized design of a supercomputing facility and to
think about what the attributes of that particular center should be. Would
it offer one-on-one collaborative assistance? Would it offer transparency
vis-a-vis using that computer or the high-end mainframe? How would it
be administered? How would it be charged out? What help would be
rendered to the users?
When only top-down decisions are made, people don't use the comput-
ers. The decision-making process has to be top-down, bottom-up, middle-
out. We focused on the bottom-up and middle-out, and then when Larry
Smarr came and mapped what he had to offer against the idealized design
that was documented and was formulated by the participation of those
whose lives would be affected by the advent of the supercomputing facility,
we found that we had an immediate, captured market.
Generally, it takes about 2 years to justify the use of a supercomputer
onsite, and it takes upwards of $250,000 to $300,000, as has been published
by the Minnesota Supercomputing Consortium. It has to be done in a
participative manner, in my opinion, or it won't work.
Mel Schmidt: Could all the panelists briefly describe how they deter-
mine allocations within their organizations? Are there any mechanisms for
billing the users?
Beverly Eccles: Within Abbott, computer resources are basically free.
The resources are supplied and the expense goes into the budget, but
individuals are not concerned about how much disk space or how much
of the central processing unit they are using. Those resources are simply
available for us, and the scientists feel very comfortable in that environment.
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97
Clifford Perry: At Kodak we have an arrangement with NCSA that
every user who logs on-and we have an administrative procedure to do
that-is billed directly in their division. We have allocated, if you will,
$100,000 chunks to sets of people.
Lawrence Tesler: At Apple as at Abbott, all the shared computer
resources that are used by more than one department are essentially free.
On our financial reports from the Apple Product Division, we break out
the entire budget for this computer operation. It is weighed as a whole as
a percent of the entire R&D budget.
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Representative terms from entire chapter:
mold flow
