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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 (...
How to make an app's background image repeat
I have set a background image in my app, but the background image is small and I want it to be repeated and fill in the whole screen. What should I do?
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How can I get the behavior of GNU's readlink -f on a Mac?
...in your own script where you'd like to call readlink -f
#!/bin/sh
TARGET_FILE=$1
cd `dirname $TARGET_FILE`
TARGET_FILE=`basename $TARGET_FILE`
# Iterate down a (possible) chain of symlinks
while [ -L "$TARGET_FILE" ]
do
TARGET_FILE=`readlink $TARGET_FILE`
cd `dirname $TARGET_FILE`
T...
Python element-wise tuple operations like sum
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Using all built-ins..
tuple(map(sum, zip(a, b)))
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What is the difference between Python's list methods append and extend?
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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...
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...
Maven build failed: “Unable to locate the Javac Compiler in: jre or jdk issue”
...s:
Add and set the JRE in menu Window → Preferences... → Java → Installed JREs:
JRE type: Standard VM JRE
Name: jdk1.6.0_18
JRE home directory: C:\Program Files (x86)\Java\jdk1.6.0_18
If this is not the case, it's possible that the brackets and spaces in the JAVA_HOME path are causing issu...
How to POST JSON Data With PHP cURL?
...re indicating Content-Type:application/json, but you are not json-encoding all of the POST data -- only the value of the "customer" POST field. Instead, do something like this:
$ch = curl_init( $url );
# Setup request to send json via POST.
$payload = json_encode( array( "customer"=> $data ) );...
How do I view the list of functions a Linux shared library is exporting?
...AL DEFAULT UND
1: 00000000 0 FUNC GLOBAL DEFAULT UND pthread_mutex_unlock@GLIBC_2.0 (4)
2: 00000000 0 FUNC GLOBAL DEFAULT UND pthread_mutex_destroy@GLIBC_2.0 (4)
3: 00000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterTMCloneTable
4: 00000000 0 FUNC ...
Calling shell functions with xargs
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Exporting the function should do it (untested):
export -f echo_var
seq -f "n%04g" 1 100 | xargs -n 1 -P 10 -I {} bash -c 'echo_var "$@"' _ {}
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 "$@"' _ {}
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