Blog Archives

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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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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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...

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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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Gone Guerrill_ R on Our Data

August 16, 2010
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Here's a summary of some things we learnt about applying R to computer performance and capacity planning data in the GDAT Class last week. Neural nets pkg nnet applied to CPU performance data in the Ripley and Venables book (see Section 8.10). How to do stacked plots that Jim calls "spark plots." Jim told...

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Go Guerrill… R on Your Data in August

July 5, 2010
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Go Guerrill… R on Your Data in August

Only one month to go! Register now for the Guerrilla Data Analysis Techniques (GDAT) class to be held during the week of August 9-13, 2010. The focus will be on using R and the PDQ-R for computer performance analysis and capacity planning.(Click on t...

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Prime Parallels for Load Balancing

July 5, 2010
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Prime Parallels for Load Balancing

Having finally popped the stack on computing prime numbers with R in Part II and Part III, we are now in a position to discuss their relevance for computational scalability.My original intent was to show how poor partitioning of a workload can defeat the linear scalability expected when full parallelism is otherwise attainable, i.e., zero...

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Linear Modeling in R and the Hubble Bubble

June 22, 2010
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Linear Modeling in R and the Hubble Bubble

Here is a scatter plot with the coordinate labels deliberately omitted. Figure 1. Do you see any trends? How would you model these data? It just so happens that this scatterplot is arguably the most famous scatterplot in history. One aficionado, writing more than forty years after its publication, commented skeptically :" data points were consequently spread...

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Playing with Primes in R (Part II)

June 17, 2010
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Playing with Primes in R (Part II)

Popping Part III off the stack—where I ended up unexpectedly discovering that the primes and primlist functions are broken in the schoolmath package on CRAN—let's see what prime numbers look like when computed correctly in R. To do this, I've had to roll my own prime number generating function.Personalizing primes in RFor what I want...

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Primes in R (Part III): Schoolmath is Broken!

June 13, 2010
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Here we are in Part III. Wait!? What happened to Parts I and II? Well, I started to write an article about Amdahl's law, parallelism and prime numbers, but found myself buried three levels deep trying to resolve problems with prime numbers in R. My normal inclination is to use Mathematica for such things, but I happened to...

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