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Use numpy array in shared memory for multiprocessing
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To add to @unutbu's (not available anymore) and @Henry Gomersall's answers. You could use shared_arr.get_lock() to synchronize access when needed:
shared_arr = mp.Array(ctypes.c_double, N)
# ...
def f(i): # could be anything numpy accepts as an index such another numpy array
with ...
Using python map and other functional tools
...earn. A fundamental rule in functional programming is that every time you call a function with the same arguments, you ALWAYS get the same output. This avoids a vipers nest of bugs introduced by having global state. As maptest depends on an external definition of bars, this principle is broken.
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Avoiding instanceof in Java
...is entry from Steve Yegge's Amazon blog: "when polymorphism fails". Essentially he's addressing cases like this, when polymorphism causes more trouble than it solves.
The issue is that to use polymorphism you have to make the logic of "handle" part of each 'switching' class - i.e. Integer etc. in ...
Why use a prime number in hashCode?
...ly be determined by the least significant entry (the one not multiplied at all). Similar entries will collide. Not good for a hash function.
31 is a large enough prime that the number of buckets is unlikely to be divisible by it (and in fact, modern java HashMap implementations keep the number of b...
check if a std::vector contains a certain object? [duplicate]
Is there something in <algorithm> which allows you to check if a std:: container contains something? Or, a way to make one, for example:
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SQL command to display history of queries
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try
cat ~/.mysql_history
this will show you all mysql commands ran on the system
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how to make svn diff show only non-whitespace line changes between two revisions
... can use
svn diff -r 100:200 -x -b > file.diff
If you want to ignore all whitespaces:
svn diff -x -w | less
Source
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Why is there no String.Empty in Java?
...would save on compile time, in fact I think it would be the latter.
Especially considering Strings are immutable, it's not like you can first get an empty String, and perform some operations on it - best to use a StringBuilder (or StringBuffer if you want to be thread-safe) and turn that into a Str...
Microsecond timing in JavaScript
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As alluded to in Mark Rejhon's answer, there is an API available in modern browsers that exposes sub-millisecond resolution timing data to script: the W3C High Resolution Timer, aka window.performance.now().
now() is better tha...
How to activate virtualenv?
... virtualenv venv --distribute
New python executable in venv/bin/python
Installing distribute.........done.
Installing pip................done.
$ source venv/bin/activate
(venv)$ python
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