Thank you to all. I think Henry insight, supported by others is the
core of what I was looking for. I appreciate all input frm all parties.
Barry Rogen
PNY Technologies, Inc.
Senior Programmer/Analyst
(973) 515 - 9700 ext 5327
bro...@pny.com
-----------------------------------------------------
We are continually faced with great opportunities
brilliantly disguised as insoluble problems.
John W
Gardner
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P Before printing please think about your environmental responsibility
-----Original Message-----
From: u2-users-boun...@listserver.u2ug.org
[mailto:u2-users-boun...@listserver.u2ug.org] On Behalf Of andy baum
Sent: Friday, July 17, 2009 5:21 AM
To: U2 Users List
Subject: Re: [U2] Universe Retrieve
Henry,
Yes, I did some more testing myself last night, should have replied
sooner. I built a file with a million records and repeated the test, I
also created an I-Descriptor on the dictionary and got the following
results :-
COUNT TESTFILE WITH F1 = "v"
Elapsed 2.828 CPU 2.171
COUNT TESTFILE WITH F1 = EVAL "'V'"
Elapsed 8.953 CPU 6.625
COUNT TESTFILE WITH F1 = VEE.ITYPE
Elapsed 8.766 CPU 6.500
Which seems to confirm what you are saying
Cheers,
Andy
----- Original Message ----
From: Henry Unger <hun...@hitech.com>
To: U2 Users List <u2-users@listserver.u2ug.org>
Sent: Friday, 17 July, 2009 0:32:03
Subject: Re: [U2] Universe Retrieve
Good point, Andy. I had considered that, but guessed that it would not
be a
significant factor.
Just in case, I created a file with a million records, and reran the
tests.
Here are the results:
COUNT TESTFILE WITH F1 = 'V'
Elapsed 7.4796
COUNT TESTFILE WITH F1 = EVAL "'V'"
Elapsed 23.2558
Seems pretty consistent with the earlier tests.
Best regards,
Henry
Henry P.. Unger
Hitech Systems, Inc.
http://www.hitech.com
-----Original Message-----
From: u2-users-boun...@listserver.u2ug.org
[mailto:u2-users-boun...@listserver.u2ug.org] On Behalf Of andy baum
Sent: Thursday, July 16, 2009 2:52 PM
To: U2 Users List
Subject: Re: [U2] Universe Retrieve
Henry,
EVAL compiles the expression and writes the result into the dictionary,
runs
the query and then deletes the dictionary item. For your test to be
valid
you would need to ignore the overheads of the compile, write to and
delete
from dictionary which in your example are significant compared to the
number
of records counted. You could probably get more accurate results by
choosing
an example that runs against a file with millions of records.
Cheers,
Andy
----- Original Message ----
From: Henry Unger <hun...@hitech.com>
To: U2 Users List <u2-users@listserver.u2ug.org>
Sent: Thursday, 16 July, 2009 18:36:27
Subject: Re: [U2] Universe Retrieve
Hi Martin,
I was under the impression that an EVAL calls the same compiler that an
I-type does, and that any expression optimization would be done therein.
Expanding beyond that, it would be interesting if the I-type compiler
was
able to detect that a particular expression does result in a constant
value
and flag the object code as not requiring repeated evaluation by the
query
processor.
Here are some empirical results using UniVerse 10.2.7:
>TIMEIT 50 COUNT VOC WITH F1 = 'V'
COUNT VOC WITH F1 = 'V'
Elapsed 1.3006
>TIMEIT 50 COUNT VOC WITH F1 = EVAL "'V'"
COUNT VOC WITH F1 = EVAL "'V'"
Elapsed 5.135
This suggests that the query processor does not detect that the result
of
the evaluation is a constant and optimize its execution.
Best regards,
Henry
TIMEIT:
sent = @SENTENCE
rest = trimf(field(sent, ' ', 2, len(sent)))
word = field(rest, ' ', 1)
if word matches "0N" then
n = int(word)
sent = trimf(field(rest, ' ', 2, len(rest)))
end else
n = 1
sent = rest
end
print sent
t0 = time()
for i = 1 to n
execute sent capturing output
next
t1 = time()
print 'Elapsed ' : t1 - t0
end
Henry P. Unger
Hitech Systems, Inc.
http://www.hitech.com
-----Original Message-----
From: u2-users-boun...@listserver.u2ug.org
[mailto:u2-users-boun...@listserver.u2ug.org] On Behalf Of Martin
Phillips
Sent: Thursday, July 16, 2009 9:30 AM
To: U2 Users List
Subject: Re: [U2] Universe Retrieve
Hi Henry,
> You can see the object code that is produced using VLIST and
> examine it for optimizations.
The particular optimsiation that Barry is looking for would not show in
the
object code. For a truly constant I-type expression, the query procesor
could evaluate it just once and store the result instead of doing it on
every use. Although not common, such I-types do exist.
Martin Phillips
Ladybridge Systems Ltd
17b Coldstream Lane, Hardingstone, Northampton, NN4 6DB
+44-(0)1604-709200
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