Emulating a hardware signed multiplier

Décio Luiz Gazzoni Filho decio at decpp.net
Sun Oct 25 02:31:33 CET 2009

On Oct 24, 2009, at 6:40 PM, Børge Strand-Bergesen wrote:

> The hardware multiplier takes two signed 64-bit numbers and produces a
> signed 128-bit number. I'm new to GMP and I'm looking for a way to
> make it interpret numbers the same way the hardware multiplier does.

You're on an XP machine, so you're on x86. I suppose you have a  
`recent' (< 5 years) processor, who then supports 64-bit extensions.  
One single 64-bit assembly signed multiply instruction does what you  
want. It executes in a couple of CPU cycles. Why complicate matters?


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