gistfile1.txt

local XB = 100000 -- give up bid threshold = 10p
local BL = 1

local ad     = tonumber(ARGV[1])
local weight = 0

-- Check if there is a weight
if tonumber(redis.call('zscore', 'ad:weights', ad)) == nil then
  return nil
end

-- Retrieve attributes
local bid, bids, wins, stake = unpack(redis.call('hmget', "ad::" .. ad, "bid", "bids", "wins", "stake"))

-- Pure paranoia: ensure we get number back
bid   = tonumber(bid)   or 0
bids  = tonumber(bids)  or 0
wins  = tonumber(wins)  or 0
stake = tonumber(stake) or 0
if stake < 0 then stake = 0 end
if bids  < 1 then bids  = 1 end

-- Calculate weight for pacing
if bid > XB then
  weight = math.floor( BL * stake/(bid) * bids/(wins+0.0001) + 0.5 )
end

-- Store weight
redis.call('zadd', 'ad:weights', weight, ad)

return weight