Re: Lua Performance, IO / Regexp

[Hans Hagen <pragma@...>]

Mariano Kamp wrote:

>   Any ideas and hints what I can do to make things faster and/or prettier?

- lpeg: much faster than string match
- no metatable: less code and less function calls (not faster here)
- binary read: no need to parse line endings in io

- the lpeg can probably be made faster (no time to look into it now)


testfile = "o.ap"

hits, hits_index = { }, { }

function whatever(ak) hits[ak] = (hits[ak] or 0) + 1 end

digit = lpeg.R("09")
pattern = (digit * digit * digit * digit * "/" * digit * digit * "/" * 
digit * digit * "/" * (1-lpeg.S(" ."))^1) / whatever
prefix = "GET /ongoing/When/" * digit * digit * digit * "x/"
suffix = " "
newline = lpeg.S("\n\r")
complete = prefix * pattern * suffix

if true then
    -- binary read 10% faster
    parser = ((1-complete)^0 * complete * (1-newline)^0 * newline)^0
    input_file = io.open(testfile,'rb')
    parser:match(input_file:read("*all"))
    input_file:close()
else
    parser = (1-complete)^0 * complete
    -- 4 times slower
    for line in io.lines(testfile) do
        parser:match(line)
    end
end

for article_key in pairs(hits) do hits_index[#hits_index+1] = 
article_key end
table.sort(hits_index, function(x,y) return hits[x] > hits[y] end)

for i, article_key in ipairs(hits_index) do
	print(i .. ". " .. article_key .. " : " .. hits[article_key])
	if i == 10 then break end
end


Hans

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