jordan@unix.cis.pitt.edu (Kenneth D Jordan) (01/08/91)
I have certain applications which can benefit substantially from being parallelized, and I can have access to a relatively new Connection machine. Before I start (or decide on how my time is best spent), I was hoping that someone with experience on a Connection Machine could answer the following questions (in no particular order): 1. How well does it perform floating point computations? I have been led to believe that the earlier models were rather poor in this respect, but that newer modess are much more proficient. How's the instruction set? How about matrix operations? 2. How tightly coupled are the processors? How much overhead is involved in getting data from one processor to another? 3. How's the operating system? UNIX-like? Mature? 4. How about high level language support? Concurrent C? Ada? Fortran? Parallel Prolog? 5. If there is high level language support, how are the debuggers? -------------------------------------------------------------------------------- Nick Nystrom Chemistry Department University of Pittsburgh nystrom@a.psc.edu --------------------------------------------------------------------------------
scp@acl.lanl.gov (Stephen C. Pope) (01/08/91)
on 7 Jan 91 20:34:43 GMT, jordan@unix.cis.pitt.edu (Kenneth D Jordan) said: Nick> I have certain applications which can benefit substantially from Nick> being parallelized, and I can have access to a relatively new Nick> Connection machine. Before I start (or decide on how my time Nick> is best spent), I was hoping that someone with experience on a Nick> Connection Machine could answer the following questions (in Nick> no particular order): Nick> 1. How well does it perform floating point computations? Nick> I have been led to believe that the earlier models were Nick> rather poor in this respect, but that newer modess are Nick> much more proficient. How's the instruction set? How Nick> about matrix operations? ``relatively new'' is not a very clear term. The issues are physical size (8k, 16k, 32k, 64k), memory size (bits/processor), and whether it has 32 or 64 bit FP chips (or none at all!). Somewhat less important is what type of host is front-ending the CM. It's important to remember that the CM was not originally built as a floating point machine (but rather for symbolic processing). It's found a new identity as an FP machine for scientific codes only rather lately. And it's getting to be a rather formidable beast of that type. We've got BIG Crays and BIG CMs here, and (modulo the nature of the code) the CM crunches like no other... (of course my employer most certainly would not officially endorse such an opinion ;-) What instruction set? With the new class of languages that TMC is delivering, you needn't even think of such things unless you really like to, and want to squander your funding squeezing out every last drop. for matrix operations: if you're talking about add/subtract of dense (or well-structured) matrices, its built in at so low a level you don't want to know. For things like tridiag solvers, FFTs, etc, there's the CM Scientific Subroutine Library which has interfaces to your favorite CM languages. Nick> 2. How tightly coupled are the processors? How much overhead Nick> is involved in getting data from one processor to another? Depends. I highly recommend that you read some of the technical literature, which will answer your questions in gory detail. Nick> 3. How's the operating system? UNIX-like? Mature? See above. The CM itself has no OS as you'd like to think of it. It's really a very expensive attached processor to a Sun or Vax front end. Nick> 4. How about high level language support? Concurrent C? Ada? Nick> Fortran? Parallel Prolog? StarLisp (data-parallel lisp), CM Fortran (a Fortran90 look-almost-alike), C-Star (a data-parallel superset of C), and C, Fortran, and Lisp bindings for Paris, one of the abstract ways of viewing the machine. There's even stuff (not from TMC) for doing C++. Nick> 5. If there is high level language support, how are the debuggers? Debuggers are never as good as they could be, but because its a SIMD machine, they're a lot more useful than many of their MIMD-based counterparts ;-) Many of your questions are ones you would ask of a distributed memory multicomputer; the CM is a *much* different beast. A little reading can go a long way! stephen pope advanced computing lab los alamos national laboratory scp@acl.lanl.gov