Fwd: Re: Window / History in Data Flow Variables

classic Classic list List threaded Threaded
2 messages Options
Reply | Threaded
Open this post in threaded view
|

Fwd: Re: Window / History in Data Flow Variables

sirinath

Sent the following to the wrong mailing list.

---------- Forwarded message ----------
From: "Suminda Dharmasena" <[hidden email]>
Date: 11 Apr 2014 12:23
Subject: Re: Window / History in Data Flow Variables
To: <[hidden email]>, <[hidden email]>
Cc:

Hi,

Any thoughts on in cooperating delay / window into GPars data flow?

Also vector / matrix / data frame /array based data flow variables.

Suminda

On 10 Apr 2014 12:45, "Suminda Dharmasena" <[hidden email]> wrote:

Is it possible to add a way to access historic values in a data flow variable.
E.g. b = a + a[-1]

b is the sum of current and previous a.

This will be useful in signal processing and technical analysis.

Reply | Threaded
Open this post in threaded view
|

Re: Fwd: Re: Window / History in Data Flow Variables

Russel Winder-3
On Fri, 2014-04-11 at 12:34 +0530, Suminda Dharmasena wrote:
[…]
> > Is it possible to add a way to access historic values in a data flow
> > variable.
> > E.g. b = a + a[-1]
> >
> > b is the sum of current and previous a.
> >
> > This will be useful in signal processing and technical analysis.

I am not convinced that this is feasible or desirable. A dataflow
variable is a single assignment entity which should be immutable once
set. A dataflow queue allows for a sequence of values, but it should be
the responsibility of the consuming operator to keep a history should it
need it. The alternative is for the operator to have a feedback queue
onto which it writes results consumed so that they can be reconsumed as
input on another queue (the a[-1] above would be am, or some such.

--
Russel.
=============================================================================
Dr Russel Winder      t: +44 20 7585 2200   voip: sip:[hidden email]
41 Buckmaster Road    m: +44 7770 465 077   xmpp: [hidden email]
London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder


---------------------------------------------------------------------
To unsubscribe from this list, please visit:

    http://xircles.codehaus.org/manage_email