Improve SortedPairs even more

[Be1zebub]

PR #2015 is good, but we can make it much better.

Improvements:

• table.insert( tbl, val ) > tbl[ #tbl + 1 ] = val
• next( keys, i ) > keys [ i ]

benchmarks:

• brandonsturgeon's version is 11.23% better than default
• my version is 36% better than default
• or 27.92% better than brandonsturgeon's

bench src: https://gist.github.com/Be1zebub/4b90791fc7ab2d89a18c7a93da143095

bench results:

benchmarks have been tested on a default branch, in p2p server.

[Kefta]

Does caching #keys and incrementing a local improve perf for large tables?

[Be1zebub]

@Kefta do you mean replace

local keys = {}

for k in pairs( tbl ) do
	keys[ #keys + 1 ] = k
end

with

local keys, i = {}, 0

for k in pairs( tbl ) do
	i = i + 1
	keys[ i ] = k
end

# doesnt actually calculate the amount, lua just get the length from the cache.

at least jit store len in cache, idk how it works in lua puc - but I has read about how jit store and process tables

but because #tbl is C-call, its 30% slower than manual calculated number usage.
we can get 2-5% more perf with this microoptimization.
Its not significant as next & table.insert replacements - because next & table.insert make some work inside.

bench results:

tested with this table:

now its 37% faster than default.

[Heyter]

:)

-- SortedPairs:
	-- sum = 0.168
	-- avg = 0.00168
	-- median = 0.0010000000000012
-- SortedPairs new:
	-- sum = 0.082000000000001
	-- avg = 0.00082000000000001
	-- median = 0.00099999999999945
do
	local pairs_aux = pairs({})
	local index, keys = 0, {}
	local sort = table.sort
	local function fn1(a, b) return a > b end
	local function fn2(a, b) return a < b end
	function SortedPairs(tbl, desc)
		keys, index = {}, 0

		for k in pairs_aux, tbl do
			index = index + 1
			keys[index] = k
		end

		sort(keys, desc and fn1 or fn2)
		return pairs_aux, tbl
	end
end