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Efficient Algorithm for Bit Reversal (from MSB->LSB to LSB->MSB) in C
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NOTE: All algorithms below are in C, but should be portable to your language of choice (just don't look at me when they're not as fast :)
Options
Low Memory (32-bit int, 32-bit machine)(from here):
unsigned int
reverse(register ...
How do I uniquely identify computers visiting my web site?
..., fingerprints changed quite
rapidly, but even a simple heuristic was usually able to guess when a fingerprint was an “upgraded” version of a previously observed browser’s
fingerprint, with 99.1% of guesses correct and a false positive rate of only
0.86%.
We discuss what privacy thr...
What is a regular expression which will match a valid domain name without a subdomain?
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This should match all cases I think: ^([a-z0-9])(([a-z0-9-]{1,61})?[a-z0-9]{1})?(\.[a-z0-9](([a-z0-9-]{1,61})?[a-z0-9]{1})?)?(\.[a-zA-Z]{2,4})+$
– transilvlad
May 16 '13 at 16:38
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Remove last item from array
..., -1) will not. Pop is of course faster but may not be always suitable for all needs.
– adelriosantiago
Sep 23 '17 at 0:40
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MemoryCache does not obey memory limits in configuration
...ximum cache size, but in my tests it does not appear that the cache is actually obeying the limits.
7 Answers
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Is inline assembly language slower than native C++ code?
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Yes, most times.
First of all you start from wrong assumption that a low-level language (assembly in this case) will always produce faster code than high-level language (C++ and C in this case). It's not true. Is C code always faster than Java code? N...
What is the best regular expression to check if a string is a valid URL?
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I wrote my URL (actually IRI, internationalized) pattern to comply with RFC 3987 (http://www.faqs.org/rfcs/rfc3987.html). These are in PCRE syntax.
For absolute IRIs (internationalized):
/^[a-z](?:[-a-z0-9\+\.])*:(?:\/\/(?:(?:%[0-9a-f][0-9a-f]...
How do I safely pass objects, especially STL objects, to and from a DLL?
How do I pass class objects, especially STL objects, to and from a C++ DLL?
4 Answers
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Why is there no xrange function in Python3?
...Some performance measurements, using timeit instead of trying to do it manually with time.
First, Apple 2.7.2 64-bit:
In [37]: %timeit collections.deque((x for x in xrange(10000000) if x%4 == 0), maxlen=0)
1 loops, best of 3: 1.05 s per loop
Now, python.org 3.3.0 64-bit:
In [83]: %timeit collec...
Execution time of C program
I have a C program that aims to be run in parallel on several processors. I need to be able to record the execution time (which could be anywhere from 1 second to several minutes). I have searched for answers, but they all seem to suggest using the clock() function, which then involves calculating...