Re: [Freeciv-Dev] Some performance issues

[Mitch Davis <mjd@xxxxxxxxxx>]

Rizos Sakellariou wrote:
> 
> Let me say here that multiplication is still an expensive operation on most
> modern processors with a cost that varies from 10 to 14 CPU cycles in many
> cases. Compilers are typically smart enough to convert multiplications of a
> variable by an integer to a series of ADDs and SHIFTs (thereby reducing
> the cost of a MUL), but they are left with no choice in the case of
> the multiplication of two unknowns as it is our case here. As a solution,
> i suggest to replace all occurrences of y*map.xsize with something like
> an array ymult[y] whose elements (from 0 to map.ysize) are precomputed
> at the beginning of each game.

Thanks for looking at this.

Having a lookup table is a good idea.  We could either have a
table with a well-known name, or a function to do a lookup.  On
compilers such as gcc, the function could be made inline.

Hmm, the table sounds neater...

Regards,

Mitch.
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