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*To*: t-discussion @ YALE*Subject*: Floating point operations.*From*: JDR@MIT-MC.ARPA*Date*: Tue ,26 Apr 83 20:35:00 EDT*Unauthentic-from*: John D. Ramsdell <JDR @ MIT-MC>

I am quite happy to hear that floating point operations will someday compile into fast code. I can understand why this is not to be done at this time. The reason it came up is that Prof. Mumford of the math department wants to do some work in object recognition which involves numeric and symbolic computations. He was quite disapointed with T. He now plannes to use Fortran; I don't know why he doesn't want to use Pascal. There is a possiblity that the numerical routines will be loaded into a process running T, so that the symbolic processing can be done in T. Who knows? The folloing results summerize our T measurements. The program used summes the integers after converting each integer to a floating point number. The best way to do this is to not use any integer arithmatic, but .... Value of limit 10000 20000 Recklessness Apple UCSD Pascal 22 44 - Apollo Pascal 4 8 - Compiled T 45 85 low Compiled T 35 63 high The T code was (define (sum-ints limit) (proclaim fixnum? limit) (do ((sum 0.0 (fl+ sum (fixnum->float count))) (count 1 (fx+ 1 count))) ; Do you proclaim sum and count ((fx> count limit) sum))) ; in the body of the do? The T code was much slower that the Apples. The apples did 32-bit arithmatic, but still. Besides the fact that floating point operations are not open coded, I found that each operation makes a new cell for the result of the operation. That is why I suggested the destructive floating point operations. As suggested by Jonathan, that is something that the compiler should do. When time permits the implementation of a optimizing numerical compiler, I look forward to seeing very interesting graphics for the Apollos running T. John PS The measurements involving fixnum operations were quite favorable. do loops turn into very fast code. I will interested in seeing how you get the factor of 2-3 speed up in new compiled code that John told me you expected.

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