Timothee.Ewart at unige.ch
Wed Feb 20 18:05:14 CET 2013
Hello GMP team,
I am working on a tiny integer arithmetic lib, based on full inline ASM mode, stack allocation, no checking. So really less possibility than GMP but sometimes a little speed up.
My lib works well, but I have something really bad, the signed determination of a signed extended multiplication (n bit * n bit = 2n bit).
What is your method to calculate an extended signed multiplication for integer represented by the two complement method ? But maybe you do not use the two complement representation.
I know the following method :
1) convert to positive and adjust the sign (what I do)
2) left/right binary shift add multiplier ( I try to combine this method with schoolbook method without success
I posted on stack overflow, it does not really help : http://stackoverflow.com/questions/14946756/mix-left-add-multiplier-school-book-algo-for-signed-multiplication)
3) booth encoding ? It seems a lot of software work
4) Extended inputs (n bit to 2n bit) and calculate the result, nice but so much more work.
5) mysterious method ?
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