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Why is transposing a matrix of 512x512 much slower than transposing a matrix of 513x513?
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The explanation comes from Agner Fog in Optimizing software in C++ and it reduces to how data is accessed and stored in the cache.
For terms and detailed info, see the wiki entry on caching, I'm gonna narrow it down here.
A cache is organized in sets and lines. At a time, only one set is u...
How to go about formatting 1200 to 1.2k in java
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Here is a solution that works for any long value and that I find quite readable (the core logic is done in the bottom three lines of the format method).
It leverages TreeMap to find the appropriate suffix. It is surprisingly more efficient than a previous solution I wrote t...
JavaScript “new Array(n)” and “Array.prototype.map” weirdness
I've observed this in Firefox-3.5.7/Firebug-1.5.3 and Firefox-3.6.16/Firebug-1.6.2
14 Answers
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iOS Image Orientation has Strange Behavior
For the past few weeks I've been working with images in objective-c and noticing a lot of strange behavior. First, like many other people, I've been having this problem where images taken with the camera (or taken with somebody else's camera and MMS'd to me) are rotated 90 degrees. I wasn't sure w...
How do I check if an integer is even or odd? [closed]
... if (x % 2)
printf("%d is odd\n", x);
return 0;
}
/* and.c */
#include <stdio.h>
int main(void)
{
int x;
for (x = 0; x < 10; x++)
if (x & 1)
printf("%d is odd\n", x);
return 0;
}
I then compiled these with gcc 4.1.3 on one of my m...
What does `someObject.new` do in Java?
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And, as you can tell, this can be incredibly confusing. Ideally, inner classes should be implementation details of the outer class and not be exposed to the outside world.
– Eric Jablow
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iOS 7 status bar back to iOS 6 default style in iPhone app?
...ost I wrote, but here is the full rundown on status bars, navigation bars, and container view controllers on iOS 7:
There is no way to preserve the iOS 6 style status bar layout. The status bar will always overlap your application on iOS 7
Do not confuse status bar appearance with status bar layou...
parseInt(null, 24) === 23… wait, what?
Alright, so I was messing around with parseInt to see how it handles values not yet initialized and I stumbled upon this gem. The below happens for any radix 24 or above.
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How can I use a file in a command and redirect output to the same file without truncating it?
...ly I want to take as input text from a file, remove a line from that file, and send the output back to the same file. Something along these lines if that makes it any clearer.
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Visual Studio SP1 error: silverlight_sdk.msi is unavailable
...ying to install the SP1 for Visual Studio 2010. I first installed the beta and it worked fine. Then I used the web platform installer to install the SQL CE Compact 4, which I assume installed the full SP1 after (this installation took over 12 hours, so I canceled it). The web platform installer told...