From: Jacob Fugal <lukfugl@...>
Date: 2006-09-12T10:19:10+09:00
Subject: Re: The economics of a slow but productive Ruby

On 9/11/06, Jacob Fugal <lukfugl@gmail.com> wrote:
>   choose FOO iff B < [(1 - Z/Y) / (X - Z/Y)](A + B)
>
> Let's apply this estimate to the current standing between .NET and
> Ruby/Rails, using the figures from Joel (X = 5, Y = 5). In this case,
> Z = 1 (actually, in my comparisons, Z was slight *less* than one).

Also note that the values I used here a pretty conservative. As many
have mentioned, Ruby will often not be the bottleneck -- X can be less
than 5. Also, depending on your programmers, Y may be more or less
than 5. Doing the calculation with X = 2 and Y = 10 yields much more
favorable results:

  (1 - Z/Y) / (X - Z/Y)
  = (1 - 1/10) / (2 - 1/10)
  = (9/10) / (19/10)
  = 9 / 19
  = 47%

So under optimistic cases, Ruby will still be economical until
hardware eats up *half* your budget. Or, pessimistically, let's try X
= 10, Y = 2:

  (1 - Z/Y) / (X - Z/Y)
  = (1 - 1/2) / (10 - 1/2)
  = (1/2) / (49/2)
  = 1/49

You're hardware budget would need to be negligible under those
circumstances to make Ruby economical.

Fortunately, in my experience, X has never even approached 5, let
alone 10. And Y has always been good to me. The important thing is
that for *your* decision, you need to:

1) Evaluate what X is *for your application*
2) Evaluate what Y you will believe
3) Know how your hardware costs will scale (see the footnote in my
original email)

All these factors will affect the outcome greatly.

Jacob Fugal