Articles by Neil Gunther

USL Scalability Modeling with Three Parameters

May 20, 2018 | 0 Comments

NOTE: Annoyingly, the remote mathjax server often takes it's sweet time rendering LaTex equations (like, up to a minute or more!!!). I don't know if this is deliberate on the part of Google or a bug. It used to be faster. If anyone knows, I'd be interested to hear; especially ...
[Read more...]

GitHub Growth Appears Scale Free

January 18, 2017 | 0 Comments

In 2013, a blogger claimed that the growth of GitHub (GH) users follows a certain type of diffusion model called Bass diffusion. Growth here refers to the number of unique user IDs as a function of time, not the number project repositories, which can have a high degree of multiplicity. In ...
[Read more...]

PDQ 7.0 Dev is Underway

May 14, 2016 | 0 Comments

The primary goal for this release is to make PDQ acceptable for uploading to CRAN. This is a non-trivial exercise because there is some legacy C code in the PDQ library that needs to be reorganized while, at the same time, keeping it consistent for programmatically porting to other languages ...
[Read more...]

PDQ 7.0 Dev is Underway

May 14, 2016 | 0 Comments

The primary goal for this release is to make PDQ acceptable for uploading to CRAN. This is a non-trivial exercise because there is some legacy C code in the PDQ library that needs to be reorganized while, at the same time, keeping it consistent for programmatically porting to other languages ...
[Read more...]

PDQ Version 6.2.0 Released

August 24, 2015 | 0 Comments

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 Version 6.2.0 Released

August 24, 2015 | 0 Comments

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...]

Hockey Elbow and Other Response Time Injuries

July 29, 2015 | 0 Comments

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...]

Hockey Elbow and Other Response Time Injuries

July 29, 2015 | 0 Comments

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...]

Restaurant Performance Sunk by Selfies

July 17, 2014 | 0 Comments

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...]

How to Remember the Poisson Distribution

July 3, 2014 | 0 Comments

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...]

Importing an Excel Workbook into R

June 5, 2014 | 0 Comments

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...]

Melbourne’s Weather and Cross Correlations

April 1, 2014 | 0 Comments

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...]

Facebook Meets Florence Nightingale and Enrico Fermi

February 19, 2014 | 0 Comments

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...]

Response Time Percentiles for Multi-server Applications

December 25, 2013 | 0 Comments

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...]

Laplace the Bayesianista and the Mass of Saturn

September 15, 2013 | 0 Comments

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...]

GDAT Class October 14-18, 2013

August 25, 2013 | 0 Comments

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...]

Exponential Cache Behavior

May 15, 2013 | 0 Comments

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...]

Adding Percentiles to PDQ

April 22, 2013 | 0 Comments

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...]

Upcoming GDAT Class May 6-10, 2013

April 22, 2013 | 0 Comments

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...]

Extracting the Epidemic Model: Going Beyond Florence Nightingale Part II

February 7, 2013 | 0 Comments

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...]
1 2 3 4

Never miss an update!
Subscribe to R-bloggers to receive
e-mails with the latest R posts.
(You will not see this message again.)

Click here to close (This popup will not appear again)