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How to sort a dataframe by multiple column(s)
...as speedy as the base R commands with their convoluted machinations. Typically brilliant Hadley Wickham work. My only gripe with it is that it breaks the standard R nomenclature where sorting objects get called by sort(object), but I understand why Hadley did it that way due to issues discussed in...
Which $_SERVER variables are safe?
...ttacker can also control and is therefore a source of an attack. This is called a "tainted" variable, and is unsafe.
2 An...
How to start two threads at “exactly” the same time
....
// Now if we block on the gate from the main thread, it will open
// and all threads will start to do stuff!
gate.await();
System.out.println("all threads started");
This doesn't have to be a CyclicBarrier, you could also use a CountDownLatch or even a lock.
This still can't make sure that ...
How to calculate a time difference in C++
...turns the CPU time consumed by the program. So if the program is run in parallel the time returned by the function would be the accumulated of the time spent on all CPUs, rather than the time elapsed cplusplus.com/reference/ctime/clock
– Ameer Jewdaki
Aug 3 '1...
Mapping over values in a python dictionary
..., f(kv[1])), my_dictionary.iteritems()))
but that's not that readable, really.
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What does the regular expression /_/g mean?
...egex matches the _ character.
The g means Global, and causes the replace call to replace all matches, not just the first one.
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How should the ViewModel close the form?
... window). You're welcome to make other tradeoffs, but it seems like a generally good deal to me.
– Joe White
May 6 '12 at 18:54
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Why is printing to stdout so slow? Can it be sped up?
...ing I decided to look into it and was quite surprised to find that almost all the time spent is waiting for the terminal to process the results.
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Spinlock versus Semaphore
...ck (or, the other way around, a lock is a special case of a semaphore). Usually, but not necessarily, spinlocks are only valid within one process whereas semaphores can be used to synchronize between different processes, too.
A lock works for mutual exclusion, that is one thread at a time can acqui...
How to validate an email address in JavaScript
...b"@gmail.com, _@gmail.com, 1@gmail.com , 1_example@something.gmail.com are all valid, but Gmail will never allow any of these email addresses. You should do this by accepting the email address and sending an email message to that email address, with a code/link the user must visit to confirm validit...