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Subject: Re: [PATCH v3] Add generic exponentially weighted moving average
 (EWMA) function
From: Peter Zijlstra <peterz@infradead.org>
To: Bruno Randolf <br1@einfach.org>
Cc: randy.dunlap@oracle.com, akpm@linux-foundation.org,
        kevin.granade@gmail.com, Lars_Ericsson@telia.com, blp@cs.stanford.edu,
        linux-kernel@vger.kernel.org
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Date: Wed, 20 Oct 2010 17:03:43 +0200
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On Wed, 2010-10-20 at 17:23 +0900, Bruno Randolf wrote:
> +/**
> + * ewma_add() - Exponentially weighted moving average (EWMA)
> + * @avg: Average structure
> + * @val: Current value
> + *
> + * Add a sample to the average.
> + */
> +struct ewma*
> +ewma_add(struct ewma *avg, const unsigned int val)
> +{
> +       avg->internal = avg->internal  ?
> +               (((avg->internal * (avg->weight - 1)) +
> +                       (val * avg->factor)) / avg->weight) :
> +               (val * avg->factor);
> +       return avg;
> +}
> +EXPORT_SYMBOL(ewma_add); 

How can it be a weighted avg if each sample has the same weight?