nather@ut-sally.UUCP (Ed Nather) (10/21/86)
In article <753@polaris.UUCP>, josh@polaris.UUCP (Josh Knight) writes: > Indeed, the proposal to use long integers is wasteful > of the very resource that is usually in short supply in these calculations, > namely memory (reference to all the "no virtual memory MY Cray!" verbage). > When Ed stores the mass of a 10 solar mass star in his simulation of the > evolution of an open cluster as a 512 bit integer, approximately 500 of > the bits are wasted on meaningless precision. I guess I didn't really make myself clear in my original posting. I didn't mean to imply that ONLY 512 bit integers would be available, but COULD be available, just as bytes and double-bytes are availble as subsets of the 32-bit integers on a Vax (ooops -- sorry, Josh). It would not be an unreasonable implementation to have registers of, say, 128 bits, so "quad integers" of 512 bits would have to be operated on in 4 pieces. My point was to substitute integer operations for floating ones and still retain workable precision. -- Ed Nather Astronomy Dept, U of Texas @ Austin {allegra,ihnp4}!{noao,ut-sally}!utastro!nather nather@astro.AS.UTEXAS.EDU
bs@linus.UUCP (Robert D. Silverman) (10/21/86)
> In article <753@polaris.UUCP>, josh@polaris.UUCP (Josh Knight) writes: > > Indeed, the proposal to use long integers is wasteful > > of the very resource that is usually in short supply in these calculations, > > namely memory (reference to all the "no virtual memory MY Cray!" verbage). > > When Ed stores the mass of a 10 solar mass star in his simulation of the > > evolution of an open cluster as a 512 bit integer, approximately 500 of > > the bits are wasted on meaningless precision. > > I guess I didn't really make myself clear in my original posting. I > didn't mean to imply that ONLY 512 bit integers would be available, but > COULD be available, just as bytes and double-bytes are availble as > subsets of the 32-bit integers on a Vax (ooops -- sorry, Josh). > It would not be an unreasonable implementation to have registers of, > say, 128 bits, so "quad integers" of 512 bits would have to be > operated on in 4 pieces. My point was to substitute integer operations > for floating ones and still retain workable precision. > -- > Ed Nather > Astronomy Dept, U of Texas @ Austin > {allegra,ihnp4}!{noao,ut-sally}!utastro!nather > nather@astro.AS.UTEXAS.EDU Such a machine is in fact being built. The machine physically resides at U. Oregon and was designed and built by Duncan Buell, Don Chiarulli and Walter Rudd. It is a 256 bit machine which can be changed dynamically at run time to act as 8 32 bit processors in parallel, as 4 64 bit processors etc. It is intended for research in computational number theory, especially integer factorization. Bob Silverman