Re:Gamma error in picture scaling
by burfog on Friday January 04, 2019 @05:26PM
(#18828301)
It's 5120 bytes for the both of them, the access is not at all random (due to color popularity), and the real cache killer is the image itself. You're dealing with a few megabytes for the image.
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Oh, the lookup tables are cached just fine. It's just that they crowd out something else.
That "something else" is already crowded out by running through a multi-megabyte image.
At least the instruction cache is barely affected, which would not be the case for a math library function.
Re:Gamma error in picture scaling
by AstralStorm on Tuesday January 08, 2019 @03:09AM
(#18854085)
You're not running a multi MB image but a small block thereof. Not that 5-6KiB LUT matters, but the extra conditional multiply ops or power or logarithm function evaluations do.
Latter are need a few MACs for a good approximation (at least 12 bit precise, preferably 16 bit - like 5th order polynomial), former have masks, worse for SIMD.