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How efficient is locking an unlocked mutex? What is the cost of a mutex?
... access to the object happens often, then multiple locks would increase parallelism. At the cost of maintainability, since more locking means more debugging of the locking.
How efficient is it to lock a mutex? I.e. how much assembler instructions are there likely and how much time do they take (...
What is the difference between Python's list methods append and extend?
...
Actually there's a big difference - x + [4, 5] gives you a new list assigned to x - x.extend() mutates the original list. I elaborate in my answer here below.
– Aaron Hall♦
Jul 17 '17 at 1...
Are duplicate keys allowed in the definition of binary search trees?
...cluded. For example, the example algorithms in the MIT Algorithms book usually present examples without duplicates. It is fairly trivial to implement duplicates (either as a list at the node, or in one particular direction.)
Most (that I've seen) specify left children as <= and right children ...
How to throw std::exceptions with variable messages?
...atter & operator << (const Type & value)
{
stream_ << value;
return *this;
}
std::string str() const { return stream_.str(); }
operator std::string () const { return stream_.str(); }
enum ConvertToString
{
to_str
};...
Calling shell functions with xargs
...
Exporting the function should do it (untested):
export -f echo_var
seq -f "n%04g" 1 100 | xargs -n 1 -P 10 -I {} bash -c 'echo_var "$@"' _ {}
You can use the builtin printf instead of the external seq:
printf "n%04g\n" {1..100} | xargs -n 1 -P 10 -I {} bash -c 'echo_var "$@"' _ {}
...
Python: using a recursive algorithm as a generator
...h a natural recursive solution. Now it happens that, even for relatively small input, the sequences are several thousands, thus I would prefer to use my algorithm as a generator instead of using it to fill a list with all the sequences.
...
How do I view the list of functions a Linux shared library is exporting?
...AL DEFAULT UND
1: 00000000 0 FUNC GLOBAL DEFAULT UND pthread_mutex_unlock@GLIBC_2.0 (4)
2: 00000000 0 FUNC GLOBAL DEFAULT UND pthread_mutex_destroy@GLIBC_2.0 (4)
3: 00000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterTMCloneTable
4: 00000000 0 FUNC ...
How to flush output of print function?
...e)
On Python 2 you'll have to do
import sys
sys.stdout.flush()
after calling print. By default, print prints to sys.stdout (see the documentation for more about file objects).
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Simple insecure two-way data “obfuscation”?
...e to figure out your keys by just assuming that you used this code as-is! All you have to do is change some of the numbers (must be <= 255) in the Key and Vector arrays (I left one invalid value in the Vector array to make sure you do this...). You can use https://www.random.org/bytes/ to gener...
How to get object length [duplicate]
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This is actually worse than using a simple loop and counter because of the added overhead of the callback function.
– nullability
Feb 19 '13 at 17:35
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