CS 240A HW0

      Ting Lei

The application I have investigated is "Elastic Properties of Concrete". It is a parallel computing project of NIST's Information Technology Laboratory. The purpose of the project is to use parallel computing methods to find out the elastic moduli of concrete (and other materials). An elastic modulus is the ratio between the stress applied on a substance and the tendency of the substence to be deformed (strain). Elastic moduli of concrete characterizes many of its non-fracture-related mechanic properties, and is in many highrise buildings, more important than the stiffness of the material. The project predicts the overall elastic moduli of concrete or any appropriate material given the 3-D image of its micro-structure and individual phase elastic moduli.

The parallel platform that they used for reporting results is an 8-CPUs SGI Origin 2000. An web search will show that this machine is of a symmetric multiprocessing (SMP) shared memory architecture. Given the number of CPUs there, I would not think it is a major supercomputer. Their code is written with MPI and Fortran 90, and it can reportedly be run on distributed memory system too.

In terms of performance, they reported a speed-up of 18 for a 3-D image of 3000^3 voxels as compared to nominal running time for the serial algorithm. As there are only 8 CPUs, the effiency would be more than 100%. Therefore I suspect there must be unfair assumptions made about the "nominal" serial program. However, I think they do achieve their goal for processing problems of larger sizes. It is obvious that if the code is 3-D image resolution is doubled on each dimension, the number of voxels will be 8 times more. Using their parallel algorithm allows processing larger pieces of the material or the same piece with finer resolutions.

I think their method will scale well to large problems because their method looks similar to finite element and there is obviously spatial locality in the problem and this can probably be exploited to decompose the computation tasks to some degree.