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Medium 9780596801700

11. High-Performance R

Adler, Joseph O'Reilly Media ePub

When possible, try to use built-in functions for mathematical computations instead of writing R code to perform those computations. Many common math functions are included as native functions in R. In most cases, these functions are implemented as calls to external math libraries. As an obvious example, if you want to multiply two matrices together, you should probably use the %% operator and not write your own matrix multiplication code in R.

Often, it is possible to use built-in functions by transforming a problem. As an example, lets consider an example from queueing theory. Queueing theory is the study of systems where customers arrive, wait in a queue for service, are served, and then leave. As an example, picture a cafeteria with a single cashier. After customers select their food, they proceed to the cashier for payment. If there is no line, they pay the cashier and then leave. If there is a line, they wait in the line until the cashier is free. If we suppose that customers arrive according to a Poisson process and that the time required for the cashier to finish each transaction is given by an exponential distribution, then this is called an M/M/1 queue. (This means memoryless arrivals, memoryless service time, and one server.)

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Medium 9780596100148

2. Basic Router Security and Access Control

Aviva Garrett O'Reilly Media ePub

In the last few years, routers have increasingly become targets of malicious hackers attempting to launch distributed denial-of-service ( DDoS) and other attacks across the Internet. Having control of a router, especially one with high-speed links, provides an even greater opportunity for mischief than just controlling PCs. A hacker in control of your router can reconfigure the system and take over your entire autonomous system (AS). Hackers are often able to log in to and take over routers simply because of negligence on the part of a router administrator who doesn't implement basic security precautions, such as setting a password for the root account, or who uses a password that can easily be discovered, such as juniper, cisco, root, or admin. Given the increasing number of malicious attacks occurring on the Internet, it is vital for you to secure your router.

This chapter talks about how to configure router access, including setting up login accounts, and other basic security measures you should take to control access to the router and to protect your router from undesired access.

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Medium 9780596521103

15. Logging, Monitoring, and Quotas

Hunter, Laura E. O'Reilly Media ePub

This chapter deals with tracking the activity and usage of various Active Directory components. When you need to troubleshoot a problem, often the first place you look is the logfiles. With Active Directory, there are several different logfiles, and each has different ways to increase or decrease the verbosity of the information that is logged. Viewing log messages can be a useful troubleshooting step, but you should also look at performance metrics to determine if system hardware or a particular service is being overutilized. In this chapter, well review a couple of ways you can view performance metrics, as well as monitor Active Directory performance. For more extensive monitoring, we suggest looking at NetPros Active Directory monitoring tools (, Microsoft System Center Operations Manager (, or similar products from other vendors such as NetIQ or Quest. In addition to the typical items that you would monitor on a Windows Server (e.g., disk space usage, physical and virtual memory errors, processor utilization), you should also monitor AD-specific performance metrics. This extends to monitoring replication activity, Event Log information, and the status of services like the File Replication Service (FRS).

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Medium 9780596101619

Show Lots of Stuff—Quickly

Rich Gibson O'Reilly Media PDF



Show Lots of Stuff—Quickly

This approach requires a little bit less code than the brute-force method, and it feels a lot more elegant. The disadvantage, of course, is that it relies on hardcoded constants that could break if Google decides to change the semantics of its zoom levels without warning, though this seems unlikely at the moment.

The Undocumented API Method

Of course, Google probably needs its own method to determine the right zoom level right? As it happens, the 1.0 version of Google Maps API does provide such a method, albeit an undocumented one. The following code makes use of this undocumented method: var center = new GPoint( (minX + maxX) / 2, (minY + maxY) / 2 ); var span = new GSize( maxX - minX, minX – minY ); var zoom = map.spec.getLowestZoomLevel(center, span, map.viewSize); map.centerAndZoom(center, zoom);

This method may be the simplest of all, but it relies on two presently undocumented features of the Google Maps API: the map.spec.getLowestZoomLevel( ) method and the map.viewSize property. Using them runs an even higher risk than the other two methods that your code will break at some point, should

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Medium 9781857547658

Five Postcards from Badenweiler for Zinovy Zinik

Iain Bamforth Carcanet Press Ltd. PDF

Five Postcards from Badenweiler for Zinovy Zinik

If it’s true that the great spa towns, those temples of propriety from Carlsbad to Vichy, are really vantage points for observing

Europe as an allegory – this was the whim of the aristocratic memoirist Charles Joseph, Prince de Ligne (-) – then

Badenweiler is the continent’s gazebo.

Tucked in the lap of a valley on the southern slopes of the Black

Forest between Freiburg and the great bend of the Rhine at Basle, a hundred kilometres south of Baden-Baden, the most famous spa of all – where Dostoevsky tried to gamble himself out of debt in the summer of  and the French collaborationists ignominiously gathered in  for what Louis-Ferdinand Céline, in his novel Nord, called ‘the “Everything Goes” Casino of History’ –

Badenweiler looks down onto the silt flats and water meadows, the Ried of Upper Alsace.

This is where the cities of the Decapolis once thrived under the

Holy Roman German Empire, centres of humanist learning like

Colmar, Selestat and Munster. Albert Schweitzer – organist, Bach scholar, theologian, humanitarian physician to French Equatorial

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