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Optimized bigint exponentiation (again)

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Ishaan Bhardwaj 2021-02-10 11:38:10 -05:00 committed by GitHub
parent 4920e5de1c
commit 32c2274bef
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1 changed files with 9 additions and 5 deletions
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10
libs/bigint/bigint.lua
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@ -147,11 +147,11 @@ function bigint.unserialize(big, output_type, precision)
-- num is the first (precision + 1) digits, the first being separated by
-- a decimal point from the others
num = num .. big.digits[1]
num = num .. math.floor(big.digits[1])
if (precision > 1) then
num = num .. "."
for i = 1, (precision - 1) do
num = num .. big.digits[i + 1]
num = num .. math.floor(big.digits[i + 1])
end
end
@ -451,15 +451,19 @@ function bigint.exponentiate(big, power)
local result = bigint.new(1)
local base = big:clone()
while (bigint.compare(exp, bigint.new(0), ">")) do
while (true) do
if (bigint.compare(
bigint.modulus(exp, bigint.new(2)), bigint.new(1), "=="
)) then
result = bigint.multiply(result, base)
end
if (bigint.compare(exp, bigint.new(1), "==")) then
break
else
exp = bigint.divide(exp, bigint.new(2))
base = bigint.multiply(base, base)
end
end
return result
end