Axel Kohlmeyer, a researcher on the project, says the best way to understand the simulation is to imagine a box filled with rubber balls, where each ball is a slightly different size and moves at a slightly different rate, interconnected with springs. Some springs are stronger or weaker than others, and some of the balls move faster or react differently. In the simulation, Kohlmeyer can follow the movements of all molecules to see the effects of anesthetics in the human body.
"Groups of particles will form and go where they like to be as determined by the magnitude of their interactions," says Kohlmeyer, explaining how the simulation evolves to the point where the interactions become balanced. Temperature variants produce vibrations and introduce new molecular activity. "The computational model is actually simple, but the challenge is you need so many millions of interactions. We do not want to just know the interactions at one point, but rather how they change over time."
Having to repeat the calculations very often is another part of the challenge, he adds.
For Kohlmeyer, the goal is to discover when the condition of not feeling anything actually occurs in the human body. This could lead to the creation of new kinds of anesthetics or help doctors determine why problems such as memory loss can occur after surgery.
Researchers at the Ohio Supercomputer Center (OSC) have found that not every simulation requires a traditional supercomputer. Don Stredney, the director and interface lab research scientist for biomedical applications at OSC, found a limitation that's common with supercomputers: Batch processes are static and run in a scheduled time frame. They cannot provide real-time interactions, so they can't mimic a real surgical procedure. Desktop workstations that cost $6,000 to $10,000 allow his team to run simulations that show, in real time, how a surgery changes a patient's anatomy, he says.
Stredney says his industry benefited from innovations in computer gaming because the standard consumer GPU became much more powerful, resulting in better realism at a much lower cost. Stredney says his researchers use commodity PCs running standard GPUs such as those from AMD's ATI unit and Nvidia, but not high-end GPU clusters. However, they find that when the data sets grow too large with some simulations, they need to return to the supercomputer.
What drives Stredney's group back to the supercomputer, he says, is the "exponentially increasing size of data sets, images in the gigabyte-per-slice range and multiscale data sets that are now routinely being acquired at half-terabyte levels." Ever-larger data sets and the complex interaction required for real-time visual and auditory simulations "require more sophisticated systems," he says.
Injection molding in automotive design
Injection-molding simulations are invaluable to car makers, Autodesk's Martin says. Injection molding is a process for producing parts from plastic materials. Simulations show whether an injection mold -- such as a bumper, for instance -- will cause denting and how the mold will fit with other parts of the car. They also reveal any defects. Designers consider many variables: the temperature of the mold, its geometric shape and how the injection-mold process will work with certain materials.
A single physical prototype of a fender can cost more than $1 million, Martin explains, so the better the simulation, the fewer prototypes that have to be built and the lower the production costs.