Neat, though I'm curious - when do instructions like this typically get used?
However, if speed is that important to you (e.g. if you are an HFT), you don't even want to be calculating the inverse square root in your hotpath. Basically, the implied volatility is "seeded" once and then you update it using greeks (finance term for a derivative, don't ask me why).
Delta is the amount an option goes up or down in price for every $ the underlying moves.
Gamma is the second derivative. The change in delta as a function of change in price of the underlying.
Theta is the amount an option goes down in price for each day you hold it (“time decay”)
Sorry if it didn't come across that way @alex_smart!
> The use of Greek letter names is presumably by extension from the common finance terms alpha and beta, and the use of sigma (the standard deviation of logarithmic returns) and tau (time to expiry) in the Black–Scholes option pricing model. Several names such as 'vega' and 'zomma' are invented, but sound similar to Greek letters. The names 'color' and 'charm' presumably derive from the use of these terms for exotic properties of quarks in particle physics.
What's with all the "presumably"?