Path: utzoo!attcan!uunet!world!decwrl!sdd.hp.com!usc!rutgers!aramis.rutgers.edu!paul.rutgers.edu!yoko.rutgers.edu!pratt From: pratt@yoko.rutgers.edu (Lorien Y. Pratt) Newsgroups: comp.ai.neural-nets Subject: Re: PDP -- McClelland & Rumelhart Message-ID: Date: 9 Oct 90 14:42:37 GMT References: <38938@eerie.acsu.Buffalo.EDU> <34624@cup.portal.com> Organization: Rutgers Univ., New Brunswick, N.J. Lines: 32 >I've been thinking of getting the pdp programs/workbook ... has anyone >worked with it enough to say the level at which the projects are written ... >i.e. is are these simple work book type programs or are they something >that could do something useful ? I've used the bp program for two years on several large applied and research projects. For the money, they are an incredible deal compared with the simulators you can buy from people by neuralworks, etc, which cost in the thousands of dollars. I hit the limit of this package when I was running a network with >1 million training patterns, >5000 network weights, on a parallel machine without an optimizing C compiler (on the order of 10^11 arithmetic operations per network training session). The program ran, but excruciatingly slowly. I had to switch to a special-purpose Fortran simulator. The problem was not in the code's usability, but in its speed with the sun C compiler that I had available, which wasn't written with supercomputer-sized applications in mind. But, until this point, I was very happy with this package and strongly recommend it to anybody getting started with neural networks. I should also say that I've modified the PDP code extensively and found it to be modularly written and very easy to change reliably, despite my initial fears, based on the lack of in-line commentary in the code. A little time invested in reverse-engineering the package and working by analogy to other program modules allowed me to add new commands and change existing functionality with relative ease. -- ------------------------------------------------------------------- L. Y. Pratt Computer Science Department pratt@paul.rutgers.edu Rutgers University Hill Center (201) 932-4634 (Hill Center office) New Brunswick, NJ 08903, USA (201) 846-4766 (home)