Blog Archives

Negative Scalability Coefficients in Excel

May 12, 2009
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Negative Scalability Coefficients in Excel

Recently, several performance engineers, who have been applying my universal scalability law (USL) to their throughput measurements, reported a problem whereby their Excel spreadsheet calculations produced a negative value for the coherency parameter (...

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Barry3-Apdex Also Lives in R

April 17, 2009
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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-s...

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PDQ 5.0 is on the Launch Pad

April 4, 2009
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PDQ 5.0 is on the Launch Pad

PDQ (Pretty Damn Quick) major release 5.0 is on the launch pad at Cape SourceForge. Because of a potential collision with the North Korean ICBM/satellite launch, we won't be filling the main liquid-hydrogen tank until next week (we don't want PDQ blame...

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Modern Microprocessor MIPS

April 2, 2009
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Modern Microprocessor MIPS

The question of how modern microprocessors compare with mainframe processors of yore, arises from time to time. The vernacular rate metric that has persisted for a long time (long in the history of computers, that is) is MIPS. Whether you approve of M...

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Streaming Hadoop Data Into R Scripts

March 23, 2009
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Streaming Hadoop Data Into R Scripts

Along the lines of Mongo Measurement Requires Mongo Management, the HadoopStreaming package on CRAN provides utilities for applying R scripts to Hadoop streaming. Hadoop is used on Amazon's EC2.

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i-Screen, u-Screen, Vee All Screen for Which Screen?

March 9, 2009
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i-Screen, u-Screen, Vee All Screen for Which Screen?

When I first came to the USA, it quickly became apparent that there was no such thing as, ice cream. You had to specify what flavor, what combination of flavors, what kind of cone, what you wanted on top of it, and so on. This is all enshrined in the s...

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Plotting PDQ Output with R

February 27, 2009
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Plotting PDQ Output with R

One the nice things about PDQ-R (coming in release 5.0) is the ability to plot PDQ output directly in R. Here's a PDQ-R script, together with the corresponding graphical output, that I knocked up to show the effect on the throughput curve of adding mor...

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PDQ-R Lives!

February 22, 2009
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PDQ-R Lives!

After some fiddling to get things linked correctly to the R binaries on my new Macbook, the first PDQ-R test model has run successfully! Here 'tiz ...This is an important step for PDQ development and is due entirely to the efforts of Phil Feller. Natur...

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Review of R in NYT and GDAT

January 8, 2009
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Review of R in NYT and GDAT

GDAT instructor, Jim Holtman, pointed me at this review of R in yesterday's New York Times. It definitely puts SAS on the defensive.Update: Another piece in the tech section of NYT.If you want to know how to apply R to performance data, sign up for th...

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How to Recover the Missing X(1) for the USL Scalability Model

July 29, 2008
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How to Recover the Missing X(1) for the USL Scalability Model

When it comes to assessing application scalability, controlled measurements of the type that can be obtained with tools like Grinder or LoadRunner, are very useful because they provide a direct measurement of the throughput, X(N), as a function of the...

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