Blog Archives

Applying PDQ in R to Load Testing

May 19, 2011
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Applying PDQ in R to Load Testing

PDQ is a library of functions that helps you to express and solve performance questions about computer systems using the abstraction of queues. The queueing paradigm is a natural choice because, whether big (a web site) or small (a laptop), all computer systems can be represented as a network or circuit of buffers and a buffer is a...

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Applying PDQ in R to Load Testing

May 19, 2011
By
Applying PDQ in R to Load Testing

PDQ is a library of functions that helps you to express and solve performance questions about computer systems using the abstraction of queues. The queueing paradigm is a natural choice because, whether big (a web site) or small (a laptop), all computer systems can be represented as a network or circuit of buffers and a buffer is a...

Read more »

Reporting Standard Errors for USL Coefficients

November 13, 2010
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In a recent Guerrilla CaP Group discussion, Baron S. wrote:....BS> Using gnuplot against the dataset I gave, I get BS>    sigma   0.0207163 +/- 0.001323 (6.385%) BS>    kappa   0.000861226 +/- 5.414e-05 (6.287%) The Gnuplot output includes the errors for each of the universal scalability law (USL) coefficients. A question about the magnitude of...

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Reporting Standard Errors for USL Coefficients

November 13, 2010
By

In a recent Guerrilla CaP Group discussion, Baron S. wrote:....BS> Using gnuplot against the dataset I gave, I get BS>    sigma   0.0207163 +/- 0.001323 (6.385%) BS>    kappa   0.000861226 +/- 5.414e-05 (6.287%) The Gnuplot output includes the errors for each of the universal scalability law (USL) coefficients. A question about the magnitude of...

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Confidence Bands for Universal Scalability Models

September 7, 2010
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Confidence Bands for Universal Scalability Models

In the recent GDAT class, confidence intervals (CI) for performance data were discussed. Their generalization to confidence bands (CB) for scalability projections using the USL model also came up informally. I showed a prototype plot but it was an ugly hack. Later requests from GDAT attendees to apply CBs to their own data meant I had...

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Confidence Bands for Universal Scalability Models

September 7, 2010
By
Confidence Bands for Universal Scalability Models

In the recent GDAT class, confidence intervals (CI) for performance data were discussed. Their generalization to confidence bands (CB) for scalability projections using the USL model also came up informally. I showed a prototype plot but it was an ugly hack. Later requests from GDAT attendees to apply CBs to their own data meant I had...

Read more »

Where to Start with PDQ?

August 30, 2010
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Where to Start with PDQ?

Once you've downloaded PDQ with a view to solving your performance-related questions, the next step is getting started using it. Why not have some fun with blocks? Fun-ctional blocks, that is. Since all digital computers and network systems can be considered as a collection of functional blocks and these blocks often contain buffers, their performance can be modeled...

Read more »

Where to Start with PDQ?

August 30, 2010
By
Where to Start with PDQ?

Once you've downloaded PDQ with a view to solving your performance-related questions, the next step is getting started using it. Why not have some fun with blocks? Fun-ctional blocks, that is. Since all digital computers and network systems can be considered as a collection of functional blocks and these blocks often contain buffers, their performance can be modeled...

Read more »

Excel Errors and Other Numerical Nightmares

August 25, 2010
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Excel Errors and Other Numerical Nightmares

Although I use Excel all the time, and I strongly encourage my students to use it for performance analysis and CaP, I was forced to include a warranty disclaimer in my GCaP book because I discovered a serious numerical error while writing Appendix B. There, my intention was just to show that Excel gives essentially the same results...

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Excel Errors and Other Numerical Nightmares

August 25, 2010
By
Excel Errors and Other Numerical Nightmares

Although I use Excel all the time, and I strongly encourage my students to use it for performance analysis and CaP, I was forced to include a warranty disclaimer in my GCaP book because I discovered a serious numerical error while writing Appendix B. There, my intention was just to show that Excel gives essentially the same results...

Read more »