Re: [foxboro] HLBL Array Question
- From: "Badura, Tom" <tbadura@xxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Thu, 15 May 2008 14:11:00 -0500
Hi Peter,
I just have a quick minute at my desk and happened to see your question.
Is it possible for you to setup your 1440 array as a circular queue and
use a pointer to point at the most recent value. That is, when it comes
time to update your latest value you increment your pointer and just
write the one new value to this location overwriting the oldest value.
You always know that the pointer points at the newest value, the next
newest is one offset below, etc. around to the oldest value in the next
position after the pointer. =20
For example
Pointer =3D 100
- Newest value is in ARHR[100]
- 2nd Newest is in ARHR[99]
- 3rd Newest is in ARHR[98]
|
|
- 3rd Oldest is in ARHR[103]
- 2nd Oldest is in ARHR[102]
- Oldest is in AHRH[101]
On next update you increment the pointer to 101 and write the new value
into AHRH[101]
Now Pointer =3D 101
- Newest value is in ARHR[101]
- 2nd Newest is in ARHR[100]
- 3rd Newest is in ARHR[99]
|
|
- 3rd Oldest is in ARHR[104]
- 2nd Oldest is in ARHR[103]
- Oldest is in AHRH[102]
Of course you have to wrap the pointer back to 1 when it reaches 1440
IF pointer < 1440 THEN
Pointer :=3D Pointer + 1;
ELSE
Pointer :=3D 1;
ENDIF;
=20
Although not in HLBL I we have used this scheme in many similar
applications. Hope this helps.
Tom Badura=20
Plastics Engineering Company
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Bruley, Peter T
Sent: Thursday, May 15, 2008 1:46 PM
To: 'Foxboro DCS Mail List' ('Foxboro DCS Mail List')
Subject: [foxboro] HLBL Array Question
Gentlemen (and Ladies)
I have a large array size is 1440 (holds 24 hours worth of 1 min
sa=3D
mples)
Every minute I want to update the 1 of the sample value and
throw o=3D
ut the oldest value.
Problem 1)
Currently I am shuffling each value 1 at a time using this loop:
----------------------------
x :=3D3D 1;
SN01 :=3D3D "Preparing Array for new value ....";
WHILE (x < 1440) DO
ARHR[x] :=3D3D ARHR[x+1]; {* throw out arry position 1 and =
shuffle
*}
x :=3D3D x + 1;
ENDWHILE;
ARHR[1440] :=3D3D RI01; {* Load newest value into array =
position
14=3D
40 *}
------------------------------
This works however just to shuffle the values takes almost 30
secon=3D
ds.
Is there a quicker way to do this ?
Is there a way to copy array position [2] through [1440] to
another a=3D
rray using a single command ?
Problem 2)
During the next step of my sequence I have to find the average
for =3D
the last 24 hours so I need to find the sum of the array then divide by
144=3D
0. I use the following loop to find the sum:
----------------------------
y :=3D3D 1;
SUM :=3D3D 0;
WHILE ( y < 1441 ) DO
SUM :=3D3D SUM + ARHR[ y ];
y :=3D3D y + 1;
ENDWHILE;
RO01 :=3D3D SUM/1440; {* 24 Hour rolling average *}
----------------------------
Again it takes about 30 seconds just to find the sum of the
array.
Is there a quicker way to find the sum of an array?
Thank You,
Peter Bruley
=20
=20
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