PDQ 5.0 Test Suite or ... How I Spent My Weekend

I was planning to blog about the amazing time I had at Velocity 2009 last week, when this landed in my mailbox (edited for space and privacy):

Subject: Seeking help with PDQ-R ...
Date: Thu, 25 Jun 2009 15:51:21 -0500

My name is James and I've been trying to learn to properly use PDQ after reading two of your books, "Guerrilla Capacity Planning" and "Analyzing Computer System Performance with Perl::PDQ." I'm still getting a grip on PDQ-R. ... I decided to set about of re-creating the queue circuit in the study with PDQ-R as an exercise. ...
The output of my code yields:
[1] "Manual response time for class 1 is 0.864179 seconds"
[1] "PDQ-R response time for class 1 is 0.313637 seconds"
[1] "Manual response time for class 2 is 6.105397 seconds"
[1] "PDQ-R response time for class 2 is 3.552873 seconds"
[1] "Manual response time for class 3 is 4.535833 seconds"
[1] "PDQ-R response time for class 3 is 4.535833 seconds"
If you could give my code a look over and give me some hints I would really appreciate it.

Barry3-Apdex Also Lives in R

As a by-product of my presentation on the Apdex Index at the NorCal CMG meeting, back in February, Guerrilla graduate, Stephen O'Connell, went off and did an implementation in R. You can read about it in this month's CMG MeasureIT and download his R-script. Free access, but requires sign-up if you're not already a member.

Apdex Index Examined

This month's edition of the CMG MeasureIT open-access journal has 2 articles on the Apdex Performance Index:

1. "The Apdex Index Revealed", by yours truly
   
2. "The Apdex Index vs Traditional Management Information Decision Tools", by Jim Brady
   

Jim's article compares the Apdex Index with other well-established management decision techniques; especially those based on statistical methods. As someone with a background in Operations Research, Jim is well placed to make these assessments. It's worth noting that Jim's paper arose out of PARS discussion he and I had at CMG'08 in Las Vegas. PARS stands for Performance Analysts' Relaxation Session (a play on mainframe LPARS) but most CMG-ers just think of it as a "free" food and booze session. ;-) I was relating to Jim that I had attended a couple of CMG presentations which tried to explain the deeper significance of the Apdex Index definitions and there were a few things that really bothered me. I thought he might be able to explain it to me in terms of mathematical statistics. We didn't resolve anything that night (what can you expect with all that booze around?), so I left it with him as homework. His paper is the outcome. You'll have to read my article to find out what was bothering me. :-)

NorCal CMG Meeting Location

For those of you who haven't attended before, the Feb 3rd (Tues) meeting of the Northern California CMG will be held in Suite 100 of the Compuware building in Pleasanton, California. Here's the Google map. Three talks will be presented:

• 9:30--10:30 Mongo Measurement Requires Mongo Capacity Management, Neil Gunther, Performance Dynamics Company
  
• 10:45--11:45 Wasted MIPS, Wanton MIPS: a MIPS Recovery Initiative, Tom Halinski, Compuware Corporation
  
• 1:00--2:00 The Apdex Index Revealed, Neil Gunther, Performance Dynamics Company
  

Breakfast starts at 8:30 am and registration is $25 at the door.

NorCal CMG Meeting Feb 3, 2009

If you're in the neighborhood, I'll be giving two talks:

1. "Mongo Measurement Requires Mongo Capacity Management"
   
2. "The Apdex Index Revealed"
   

at the next meeting of the Northern California Computer Measurement Group.

Apdex Meets Apex

The Apdex Alliance has defined a performance metric, called the Apdex index, which rates the measured response times of distributed applications from an Internet user perspective. The Apdex index is constructed from three categories which are defined by partitioning the total number of sample counts (C) according to an agreed upon threshold time (τ):

1. Satisfied (0 < S < τ)
2. Tolerating (τ < T < 4τ)
3. Frustrated (F > 4τ)