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From "Leo Sutic" <leo.su...@inspireinfrastructure.com>
Subject RE: Adaptive Caching [was Re: initial checkin of the Scheme code]
Date Thu, 13 Dec 2001 15:51:03 GMT


> From: Berin Loritsch [mailto:bloritsch@apache.org]
> Stefano Mazzocchi wrote:
>
> I
> don't know
> what the letter above the sigma or below the sigma is supposed to signify.

The sigma is like a summing for-loop. Example:

> >
> >                n
> >                --
> >  Invalid(r) =  \  (V(r,I ) + Pc(r,I ) + s(r,I ))
> >                /        i          i         i
> >                --
> >               i = 1
> >

would be like (with an asuumption of data types):

float Invalid (float r) {
  float sum = 0.0;
  for (int i = 1; i <= n; i++) {
    sum += (V(r,I[i]) + Pc(r,I[i]) + s(r,I[i]))
  }
  return sum;
}

So, you can read the sigma as "sum of <expression after sigma> for all
integer values of <whatever variable is below the sigma> between <the
variable below the sigma's initial value> and <the value or variable on top
of the sigma>". For the above: "sum of (V(r,Ii) + Pc(r,Ii) + s(r,Ii)) for
all integer values of i between 1 and n".

/LS


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