That was a really interesting article so I took the example, expanded it to
include an object property and ran the test on my system.
Here are my results:
---------------------------------
y=1
nsec=SECONDS()
FOR i = 1 to 1000000
* x=y && Results: 0.377
* x=m.y && Results: 0.151
* x=fld255 && Results: 0.328
* x=test.fld255 && Results: 0.201
* x=objSession.nValue && Results: 0.377
ENDFOR
?SECONDS()-nsec
---------------------------------
Most of my work is done moving data through temporary cursors and I ALWAYS
reference fields with the table.field method shown in the fourth test. I
also often use object properties to store static variables. While it looks
like I'm getting the best results using table.field access; I'm not getting
any performance advantage using object properties or by not using the m.
prefix. The good news is now I know if I'm going to do a LOT of iterations
with memory variables, there are some performance gains to be picked up by
simply using the m. notation. I think I may keep these results in mind when
I'm doing refactoring on my function library!
This has been quite the learning experience and I really appreciate Ken for
sharing that article! It also proves that no matter how long you've been
programming in ANY language there is always something new you can pick up.
Thanks!
Paul H. Tarver
Tarver Program Consultants, Inc.
Email: p...@tpcqpc.com
-----Original Message-----
From: ProfoxTech [mailto:profoxtech-boun...@leafe.com] On Behalf Of Ken
Dibble
Sent: Tuesday, August 01, 2017 1:30 PM
To: profoxt...@leafe.com
Subject: RE: GETFILE() Returns Empty String in Some Cases
I remember!! It was Calvin Hsia! Here's the blog article:
https://blogs.msdn.microsoft.com/calvin_hsia/2004/12/14/foxpro-performance-t
ip-field-name-lookup-for-tables/
Ken
>On 2017-08-01 10:00, Ken Dibble wrote:
>>A member of the VFP Team (I can't remember his name; he was the guy
>>who "took out the slow parts" from various subsystems for VFP 8 and 9)
>>wrote a blog article explaining that without the M. prefix, the system
>>MUST compare every variable referenced to every field in the current
>>work area every time the variable is accessed to determine whether the
>>variable is a field name. He said that if the current work area
>>contains a large number of fields, and the same variable is used over
>>a large number of iterations in a tight loop, using the M. prefix
>>makes a considerable difference in speed. He showed test results to
>>demonstrate this.
>>I do a LOT of array iteration. So I began using the M. prefix for
>>variables inside high-iteration tight loops. I noticed a slight speed
>>increase.
>>However, I find the M. prefix ugly and distracting. I used it
>>yesterday as a quick fix to demonstrate what the problem was. I will
>>probably eventually rename the variable.
>>Ken
>
>
>Very interesting...thanks for sharing that!
>
[excessive quoting removed by server]
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