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PDQ (Pretty Damn Quick) is a FOSS performance analysis tool based on the paradigm of queueing models that can be programmed natively in R Python Perl C and several other languages. This minor release is now available for download. If you're new to PDQ, here's a simple queueing model written ... [Read more...]

PDQ (Pretty Damn Quick) is a FOSS performance analysis tool based on the paradigm of queueing models that can be programmed natively in R Python Perl C and several other languages. This minor release is now available for download. If you're new to PDQ, here's a simple queueing model written ... [Read more...]

You've heard of tennis elbow. Well, there's a non-sports, performance injury that I like to call hockey elbow. An example of such an "injury" is shown in Figure 1, which appeared in a recent computer performance analysis presentation. It's a reminder of how easy it is to become complacent when doing ... [Read more...]

You've heard of tennis elbow. Well, there's a non-sports, performance injury that I like to call hockey elbow. An example of such an "injury" is shown in Figure 1, which appeared in a recent computer performance analysis presentation. It's a reminder of how easy it is to become complacent when doing ... [Read more...]

An interesting story appeared over the weekend about a popular NYC restaurant realizing that, although the number of customers they served on a daily basis is about the same today as it was ten years ago, the overall service has significantly slowed. Naturally, this situation has led to poor online ... [Read more...]

The Poisson cumulative distribution function (CDF) \begin{equation} F(α,n) = \sum_{k=0}^n \dfrac{α^k}{k!} \; e^{-α} \label{eqn:pcdf} \end{equation} is the probability of at most $n$ events occurring when the average number of events is α, i.e., $\Pr(X \le n)$. Since \eqref{eqn:pcdf} is ... [Read more...]

The usual route for importing data from spreadsheet applications like Excel or OpenOffice into R involves first exporting the data in CSV format. A newer (c. 2011) and more efficient CRAN package, called XLConnect, facilitates reading an entire Excel workbook and manipulating worksheets and cells programmatically from within R. XLConnect doesn't ... [Read more...]

During a lunchtime discussion among recent GCaP class attendees, the topic of weather came up and I casually mentioned that the weather in Melbourne, Australia, can be very changeable because the continent is so old that there is very little geographical relief to moderate the prevailing winds coming from the ... [Read more...]

Highlighting Facebook's mistakes and weaknesses is a popular sport. When you're the 800 lb gorilla of social networking, it's inevitable. The most recent rendition of FB bashing appeared in a serious study entitled, Epidemiological Modeling of Online Social Network Dynamics, authored by a couple of academics in the Department of Mechanical ... [Read more...]

In a previous post, I applied my rules-of-thumb for response time (RT) percentiles (or more accurately, residence time in queueing theory parlance), viz., 80th percentile: $R_{80}$, 90th percentile: $R_{90}$ and 95th percentile: $R_{95}$ to a cellphone application and found that the performance measurements were not completely consistent. Since the data ... [Read more...]

I'm reviewing Bayes' theorem and related topics for the upcoming GDAT class. In its simplest form, Bayes' theorem is statement about conditional probabilities. The probability of A, given that B has occurred, is expressed as: \begin{equation} \Pr(A|B) = \dfrac{\Pr(B|A)\times\Pr(A)}{\Pr(B)} \label{... [Read more...]

This is your fast track to enterprise performance analysis and capacity planning with an emphasis on applying R statistical tools to your performance data. Early-bird discounts are available for the Level III Guerrilla Data Analysis Techniques class O... [Read more...]

Guerrilla alumnus Gary Little observed certain fixed-point behavior in simulations where disk IO blocks are updated randomly in a fixed size cache. For his python simulation with 10 million entries (corresponding to an allocation of about 400 MB of memory) the following results were obtained: Hit ratio (i.e., occupied) = 0.3676748 Miss ratio (... [Read more...]

Pretty Damn Quick (PDQ) performs a mean value analysis of queueing network models: mean values in; mean values out. By mean, I mean statistical mean or average. Mean input values include such queueing metrics as service times and arrival rates. These could be sample means. Mean output values include such ... [Read more...]

Enrollments are still open for the Level III Guerrilla Data Analysis Techniques class to be held during the week May 6—10. Early-bird discounts are still available. Enquire when you register. As usual, all classes are held at our lovely Larkspur... [Read more...]

This is the second of a two part reexamination of Florence Nightingale's data visualization based on her innovative cam diagrams (my term) shown in Figure 1. Figure 1. Nightingale's original cam diagrams (click to enlarge)RecapIn Part I, I showed that FN applied sectoral areas, rather than a pie chart or conventional ... [Read more...]