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Simple explanation of MapReduce?
...want all without you knowing how it loops over all the records.
There are indexes and keys and joins and views and a lot of stuffs a single database could hold, so by shielding you against how the data is actually stored, your code are made easier to write and maintain.
Same goes for parallel prog...
How do I write the 'cd' command in a makefile?
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It is actually executing the command, changing the directory to some_directory, however, this is performed in a sub-process shell, and affects neither make nor the shell you're working from.
If you're looking to perform more tasks wit...
How to specify new GCC path for CMake
... path /usr/bin/gcc . But it is old, I need a new version of gcc. So I install a new version in a new path /usr/local/bin/gcc .
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Using Linq to get the last N elements of a collection?
...s. (The .NET 4.0 implementation will copy the collection to an array, and index backward off it)
– James Curran
May 4 '16 at 19:43
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How is the undo tree used in Vim?
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See also :h undo-redo, which lists all the commands and their usage.
There are two ways to traverse the undo tree. One is to go "back in time". g+ and g- will traverse all of the nodes in the tree in chronological or reverse-chronological order (which can...
Count how many records are in a CSV Python?
...aranteed to be a fixed size, so the only way to count them is to read them all.
– Martijn Pieters♦
Apr 19 '13 at 15:55
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Longest line in a file
...ing for a simple way to find the length of the longest line in a file. Ideally, it would be a simple bash shell command instead of a script.
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How to use clock() in C++
How do I call clock() in C++ ?
7 Answers
7
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What is a memory fence?
...ead/writes occur in the order you expect. For example a 'full fence' means all read/writes before the fence are comitted before those after the fence.
Note memory fences are a hardware concept. In higher level languages we are used to dealing with mutexes and semaphores - these may well be implemen...
Python dictionary: Get list of values for list of keys
...n list-comp:
Build list and throw exception if key not found: map(mydict.__getitem__, mykeys)
Build list with None if key not found: map(mydict.get, mykeys)
Alternatively, using operator.itemgetter can return a tuple:
from operator import itemgetter
myvalues = itemgetter(*mykeys)(mydict)
# use ...