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How efficient is locking an unlocked mutex? What is the cost of a mutex?
... it causes to much of the inter-CPU/core traffic to flush the mutex memory from the data cache of other CPUs to guarantee the cache coherency. The cache flushes are like light-weight interrupts and handled by CPUs transparently - but they do introduce so called stalls (search for "stall").
And the ...
Why do assignment statements return a value?
...he OP's "should", and make assignments have no value or otherwise ban them from being subexpressions. I think that's an overreaction to the =/== typo, which is easily addressed by disallowing using the value of = unless it is parenthesed. e.g., if ((x = y)) or if ((x = y) == true) is allowed but if ...
Are JavaScript strings immutable? Do I need a “string builder” in JavaScript?
...n enumerates the array internally, so it's not cheating to omit a for loop from the join test, either).
– Roy Tinker
Jul 22 '13 at 18:18
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Can code that is valid in both C and C++ produce different behavior when compiled in each language?
...haracter ('a') in C/C++ for an explanation of the difference.
Another one from this article:
#include <stdio.h>
int sz = 80;
int main(void)
{
struct sz { char c; };
int val = sizeof(sz); // sizeof(int) in C,
// sizeof(struct sz) in C++
prin...
Changing Mercurial “Default” Parent URL
Let's say I have a Mercurial repository and I'm pulling from a default parent URL (the source I cloned it from).
3 Answers
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Django connection to PostgreSQL: “Peer authentication failed”
...ocalhost to the HOST setting and it worked.
Here is the DATABASES section from my settings.py.
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql_psycopg2',
'NAME': '<MYDATABASE>',
'USER': '<MYUSER>',
'PASSWORD': '<MYPASSWORD...
Converting a string to a date in JavaScript
...
// Please pay attention to the month (parts[1]); JavaScript counts months from 0:
// January - 0, February - 1, etc.
var mydate = new Date(parts[0], parts[1] - 1, parts[2]);
console.log(mydate.toDateString());
sha...
Python : List of dict, if exists increment a dict value, if not append a new dict
...ecial data structure, defaultdict, created just to make this even easier:
from collections import defaultdict # available in Python 2.5 and newer
urls_d = defaultdict(int)
for url in list_of_urls:
urls_d[url] += 1
If you access the defaultdict using a key, and the key is not already in the ...
.NET data structures: ArrayList, List, HashTable, Dictionary, SortedList, SortedDictionary — Speed,
...
from msdn, it seems like sortedList implement IDictionnary - not IList
– Haim Bendanan
Nov 23 '16 at 18:45
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When to use generic methods and when to use wild-card?
I am reading about generic methods from OracleDocGenericMethod . I am pretty confused about the comparison when it says when to use wild-card and when to use generic methods.
Quoting from the document.
...