Nice trick to compute the numerical derivative in python!

Some while back, I found myself sitting next to an accomplished economics professor at a dinner event. Shortly after pleasantries, I said to him, “economic growth cannot continue indefinitely,” just to see where things would go. It was a lively and informative conversation. I was somewhat alarmed by the disconnect between economic theory and physical constraints—not for the first time, but here it was up-close and personal. Though my memory is not keen enough to recount our conversation verbatim, I thought I would at least try to capture the key points and convey the essence of the tennis match—with some entertainment value thrown in.

Cast of characters: Physicist, played by me; Economist, played by an established economics professor from a prestigious institution. Scene: banquet dinner, played in four acts (courses).

It is hard to represent our spherical world on flat piece of paper. Cartographers use something called a "projection" to morph the globe into 2D map. The most popular of these is the Mercator projection.

Every map projection introduces distortion, and each has its own set of problems. One of the most common criticisms of the Mercator map is that it exaggerates the size of countries nearer the poles (US, Russia, Europe), while downplaying the size of those near the equator (the African Continent). On the Mercator projection Greenland appears to be roughly the same size as Africa. In reality, Greenland is 0.8 million sq. miles and Africa is 11.6 million sq. miles, nearly 14 and a half times larger.

Summary

· Shell Extension ( right-click on files and folders in Windows Explorer )
· Manage ReadOnly, Hidden, Archive, System, Compress and Index attributes
· Manage Created, Modifed and Accessed date and time stamps
· Manage photo ( EXIF ) date and time stamps
· Apply absolute and offset values to date and time
· Apply random date and time stamps
· Synchronise date and time stamps
· Change case of file and folder names and extensions
· Apply filters on selection to restrict processing
· Realtime and detailed reporting
· Simulation mode
· Extensive, localized user guide in PDF format
· Attribute Changer is free, even for commercial use

nssm monitors the running service and will restart it if it dies. With nssm you know that if a service says it's running, it really is. Alternatively, if your application is well-behaved you can configure nssm to absolve all responsibility for restarting it and let Windows take care of recovery actions.

nssm logs its progress to the system Event Log so you can get some idea of why an application isn't behaving as it should.

nssm also features a graphical service installation and removal facility.

Say you have carefully tuned your database and wow! it is ten times faster -- but, before you push it to the production cluster, how do you know the answer of the query is correct?   Or at least, same as before?   :-)    You may have same question if you want to upgrade or migrate your database, or, for us, we want to make sure the new great join algorithm actually produce correct answer.   Well, let's just put the result before, and after, in two tables, and compare the two tables.

This is great, but turns out to be quite tricky.   You need to take care of the cases that,

     Either table may not have a primary key
     Rows in the two tables may be physically stored in different orders.
    Columns could contain nulls.
    The two tables could be huge, so performance must be good.

Here are something you could do.

[Condensed mirror of the pitfalls, see the page for details]

1. Forgetting or mistyping the package name: Since Java is case-sensitive, the package name must be exact.

2. Mistyping the class name. As with package names, Java class names are also case-sensitive. Beware of cases of O/0 (capital-”o” vs. the digit zero), and I/l/1 (capital-”i” vs. lowercase “L” vs. the digit 1). Also note whether the class name includes the underscore (“_”) character.
     
3. Using a Java class that was compiled using a newer JDK major-version than the JVM used in Matlab.

4. Forgetting to update the Java classpath.

5. Dependency #1: A class that depends on any other class that is not on the current Java classpath (either dynamic or static).

6. Dependency #2: A class on the static Java classpath that depends on another class which is on the dynamic Java classpath. All static classes must depend only on other static classes, since the static classpath is processed before the dynamic one, when the JVM is launched at Matlab startup.
     
7. Non-public class – Matlab can only access public classes. If the class is private, protected or has package visibility (by not specifying any visibility modifier at all), then the class would not be loadable by Matlab, only by other Java classes. So remember to add the public keyword in the definition of all the Java classes that you wish to directly use in Matlab.
     
8. Non-public constructor – Matlab can only create objects for non-static classes that have public constructors. If all the class constructors are non-public, then Matlab cannot create a class instance object. In such a case we would get a misleading error message, that at least hints that the problem is with the constructor.

Many programs use regular expression to find & replace text. However, they tend to come with their own different flavor.

You can probably expect most modern software and programming languages to be using some variation of the Perl flavor, "PCRE"; however command-line tools (grep, less, ...) will often use the POSIX flavor (sometimes with an extended variant, e.g. egrep or sed -r). ViM also comes with its own syntax (a superset of what Vi accepts).

This cheatsheet lists the respective syntax of each flavor, and the software that uses it.

Imapfilter is a mail filtering utility written in Lua which connects to one or more IMAP accounts and filters on the server using IMAP queries. It is a lightweight command line utility, the configuration can be versioned and is simple text and it is very fast.

Have you ever been on a pentest, or troubleshooting a customer issue, and the "next step" was to capture packets on a Windows host?  Then you find that installing winpcap or wireshark was simply out of scope or otherwise not allowed on that SQL, Exchange, Oracle or other host?  It used to be that this is when we'd recommend installing Microsoft's Netmon packet capture utility, but even then lots of IT managers would hesitate about using the "install" word in association with a critical server.  Well, as they say in networking (and security as well), there's always another way, and this is that way.

"netsh trace" is your friend.  And yes, it does exactly what it sounds like it does.