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Subject: Re: Maths: Fair match between programs on uneven machines

Author: David Paulowich

Date: 10:50:56 02/15/00

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On February 15, 2000 at 09:12:25, Shep wrote:

>Hi all,
>
>I was trying to write this post earlier, but found a flaw in my calculations, so
>here goes the fixed one:
>
>Suppose you want to play a match on two machines with PB and only have two
>machines of different speed. (Obviously, just adjusting the time controls to
>reflect the speed difference won't make it fair.)
>
>Assume that machine A is the faster one and that machine B is slower by a factor
>of k>1. The natural impulse would be to give machine B k-times as much
>reflection time.
>For simplicity, let's assume that both machines predict precisely 50% of their
>opponent's moves. Then the effective reflection times for both side are:
>
>  R_a(k) = 1+k/2
>  R_b(k) = k+1/2
>
>Both reflection time functions are linear in k and intersect at k=1, thus it's
>easy to see that
>
> R_a(k) < R_b(k)  for all k>1
>
SKIP
>---
>Shep

I am still trying to shake off a winter cold, but I will give this a try.
THERE IS NO SOLUTION FOR k = 2 (OR GREATER).

Suppose the slow machine plays game/m hours and the k-times as fast machine
plays game/1 hour.  Following your calculations, with 50% success rate for
predictions, we obtain effective reflection times of:
R(slow) = m + 0.5  hours = 28.5 hours when m = 28
R(fast) = k(1 + 0.5m)  hours = 28.5 hours when m = 28 and k = 1.9

Solving the equation: m + 0.5 = k(1 + 0.5m)  gives the formula:
m = (2k -1)/(2 - k) for values of "k" between 1 and 2.  For example,
m = 298 when k = 1.99  No matter how large "m" gets, you cannot handle
a speed advantage "k" greater than 2, assuming the machines have a
50% success rate in pondering.



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