[Equest-users] User-Defined Default Expressions
Aaron Powers via Equest-users
equest-users at lists.onebuilding.org
Sun Mar 5 19:25:44 PST 2017
To expand on Nick's trick below, I wanted to share why only the 1st 4
characters are returned by default and why his code works (this is mostly a
guess from reverse-engineering the source code, but it's consistent with
the way the actual program works).
Old versions of Fortran had no built-in character or string data types, so
programmers had to use tricks to deal with them. This would have been true
of the dialect of Fortran used in the original DOE2.1A, and so a form of
the original technique used to deal with string literals persists in the
code today. As a warning, this next part may give the mechanical engineers
out there a headache... A single character is traditionally encoded in
ASCII using a single byte. A byte is 8 bits, and the largest 8 bit number
is 11111111 = 255, so you can encode 256 unique characters using a single
byte. As an example, the btye 01100001 = 97 represents the character 'a'
in ASCII. The smallest built-in data type in early Fortran was the integer
(or float) which is encoded using 4 bytes. The trick used in DOE2 is to
encode string literals as an array of 8 integers (or float), and since each
integer contains 4 bytes (i.e. 4 characters), the entire string array
represents a total of 8x4 = 32 characters. This is why there's a 32
character limit on string fields. So accessing the first element of this
array by #L("C-ACTIVITY-DESC") or #L("C-ACTIVITY-DESC",0) returns the first
4 characters, #L("C-ACTIVITY-DESC",1) returns the second 4 characters, and
so on.
Now a little further into the weeds (this is more speculation into how it
could be done rather than how it's actually done under the DOE2 hood).
Consider the string 'abcd'. This can be encoded into a single integer by
making the four bytes of the integer be the same as the 4 character's ASCII
representation in sequence together. So the first byte is 97(01100001),
the second 98(01100010), the third 99(01100011), and the fourth
100(01100100). Also, in Fortran, integers are encoded in little-endian
style which just means that we need to order the bytes in reverse order
when constructing the integer. The entire integer in binary form is then
01100100011000110110001001100001. The value of this integer in decimal
is 1684234849. So, in DOE2-Land, the number 1684234849 is equivalent to
'abcd'.
However, it appears that you can't access the integer representation of
these four character 'words' in keyword expressions. For example:
if ("abcd" == 1684234849) then ... produces an error.
Also, you can't do arithmetic with the integer representation.
Interestingly though, the '+' operator functions as a concatenate operator
when dealing with string literals. This can be used to compare the first
4, 8, 12, ... characters of a string. For example, try the following code
for the lighting power density of a space. This expression considers the
first 8 characters when checking the C-ACTIVITY-DESC field. This could be
expanded to check all 32 characters, although the code would get a little
bloated.
switch(#L("C-ACTIVITY-DESC",0) + #L("C-ACTIVITY-DESC",1))
case "office": 1.1
case "kitchen": 1.5
case "restroom": 0.7
default: 1.0
endswitch
In this code, the result when C-ACTIVITY-DESC = "office" is 1.1, but the
result when C-ACTIVITY-DESC = "office1" is 1.0.
Aaron
*From:* Nicholas Caton [mailto:Nicholas.Caton at schneider-electric.com]
*Sent:* Friday, March 03, 2017 4:04 PM
*To:* Bishop, Bill <bbishop at pathfinder-ea.com>; Chris Jones
<Christopher.Jones at RWDI.com>; Michael Campbell <mcamp1206 at gmail.com>
*Cc:* equest-users at onebuilding.org
*Subject:* RE: [Equest-users] User-Defined Default Expressions
Appending to this, while ("C-ACTIVITY-DESC") returns the first 4 characters
by default, if you ever need to further distinguish inputs within spaces
sharing the same/similar activity descriptors, you can also reference the 2
nd set of 4 characters (or the 3rd set, or the 4th set…).
To do this, append the optional argument “,#” wherever you’d normally
specify “C-ACTIVITY-DESC.”
To build on the running example, say you had 2 tenants to distinguish in a
building with “Retail” space, but they had two different occupancy
densities. You could handle that by first adding to their descriptors,
such as follows:
Retail_–_Best Buy
Retail_–_Home Depot
The first 4 characters for each case are the same: “RETA” (list position
0). The second set of 4 is “IL_–“ (list position 1). The third set is
finally distinguishable: “_BES” and “_HOM” (list position 2).
>From here you could either insert an if/then statement for the “Reta” case,
or just nest another switch statement. Added some formatting for clarity,
but highlightedthe new addition:
AREA/PERSON =
{if(#SV(#L("ZONE-TYPE"))==2) then no_def else
if(#RV(#L("PEOPLE-SCHEDULE"))!=0) then unused else
switch (#L("C-ACTIVITY-DESC"))
case "Reta": switch (#L("C-ACTIVITY-DESC",2))
case “_Bes” : 67
case “_Hom” : 67*2
default : 500
endswitch
case "Lobb": 150
case "Clas": 100
default: 500
endswitch
endif
endif}
~Nick
*Nick Caton, P.E., BEMP*
Senior Energy Engineer
Regional Energy Engineering Manager
Energy and Sustainability Services
Schneider Electric
D 913.564.6361 <(913)%20564-6361>
M 785.410.3317 <(785)%20410-3317>
F 913.564.6380 <(913)%20564-6380>
E nicholas.caton at schneider-electric.com
15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States
*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org
<equest-users-bounces at lists.onebuilding.org>] *On Behalf Of *Bishop, Bill
via Equest-users
*Sent:* Friday, March 03, 2017 12:24 PM
*To:* Chris Jones <Christopher.Jones at RWDI.com>; Michael Campbell <
mcamp1206 at gmail.com>
*Cc:* equest-users at onebuilding.org
*Subject:* Re: [Equest-users] User-Defined Default Expressions
Mike,
You can start with the expression below. Paste only the text between the
brackets if you are pasting within the interface. If pasting into the input
file, this would go after “SET-DEFAULT FOR SPACE”. Like Chris said, the
case statement names should be four characters or less. However, they are
not case sensitive, so upper/lower case doesn’t matter.
~Bill
AREA/PERSON =
{if(#SV(#L("ZONE-TYPE"))==2) then no_def else
if(#RV(#L("PEOPLE-SCHEDULE"))!=0) then unused else
switch (#L("C-ACTIVITY-DESC"))
case "Reta": 67
case "Lobb": 150
case "Clas": 100
default: 500
endswitch
endif
endif}
*William Bishop, PE, BEMP, BEAP, CEM, LEED AP **|** Pathfinder Engineers &
Architects LLP*
*Senior Energy Engineer*
134 South Fitzhugh Street Rochester, NY 14608
*T: (585) 698-1956 <(585)%20698-1956>* F: (585)
325-6005
bbishop at pathfinder-ea.com <wbishop at pathfinder-ea.com>
www.pathfinder-ea.com
[image: http://png-5.findicons.com/files/icons/977/rrze/720/globe.png]Carbon
Fee and Dividend - simple, effective, and market-based.
*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org
<equest-users-bounces at lists.onebuilding.org>] *On Behalf Of *Chris Jones
via Equest-users
*Sent:* Friday, March 03, 2017 12:52 PM
*To:* Michael Campbell <mcamp1206 at gmail.com>
*Cc:* equest-users at onebuilding.org
*Subject:* Re: [Equest-users] User-Defined Default Expressions
Note, only the first 4 characters of the C-ACTIVITY-DESC field are
recognized in user defined expressions. Therefore, if your UDF uses
“RETAIL” as the test, it may fail because only “RETA” is used.
Other than that, I suggest reviewing the BDLDFT.TXT file in the eQUEST 3-65
Data folder. It is full of example default expressions.
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*Christopher Jones, **P.Eng. *| Senior Energy Analyst
*RWDI*
901 King Street West, Suite 400, Toronto, ON M5V 3H5 Canada
Tel: (519) 823-1311 ext 2052 <(519)%20823-1311>
rwdi.com <http://www.rwdi.com/>
*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org
<equest-users-bounces at lists.onebuilding.org>] *On Behalf Of *Michael
Campbell via Equest-users
*Sent:* Friday, March 03, 2017 12:32 PM
*To:* equest-users
*Subject:* [Equest-users] User-Defined Default Expressions
Hi eQUEST Users,
I'm trying to create default user expressions in an effort to auto-populate
certain fields in my models.
I want to reference the activity description (C-ACTIVITY-DESC) have it
automatically fill in fields such as Area/Person.
So for this example, I'm trying to make all spaces that have Activity
Description of "RETAIL" to be populated with a Area/Person value of 67.
I've tried using the "Switch" function and if-then statements but haven't
been able to get it to work.
Any assistance is appreciated.
Thank you,
Mike Campbell
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