In the event the object is outside its domain, the worst case search time is logarithmic, much as the worst case Legion object location time. As in Legion, an object can be located by traversing the location tree from the root until the object is located. Our second stop is in Potsdam, Germany, where at the Albert Einstein Institute Thomas Radke and Ed Seidel are working on the Cactus project. Cactus is best described as a software engineering veneer over a set of very hairy parallel numerical scientific algorithms, mainly bent on solving Einstein's highly coupled, nonlinear hyperbolic elliptical partial differential gravitational wave equations in three-dimensions. There are dozens of thorns available, some of which provide overlapping functionality.
Cactus operates efficiently by using a two-stage compilation process.
To produce a Cactus executable, the user first decides which thorns are necessary to solve the problem of interest. In the first compilation stage the user, through a complex set of perl scripts, hard-codes these modules into the Cactus flesh. As a parallel grid application Cactus is special because it takes a sizeable step towards efficiently separating disiplinary scientists from the significant computational science required to execute parallel applications. Often, transparency is a double-edged sword. Cactus has done a good job of providing a scientific code that is both flexible and high-performance.