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Simple explanation of MapReduce?
...
Take a bunch of data
Perform some kind of transformation that converts every datum to another kind of datum
Combine those new data into yet simpler data
Step 2 is Map. Step 3 is Reduce.
For example,
Get time between two impulses on a pair of pressure meters on the road
Map those ti...
Is there a REAL performance difference between INT and VARCHAR primary keys?
Is there a measurable performance difference between using INT vs. VARCHAR as a primary key in MySQL? I'd like to use VARCHAR as the primary key for reference lists (think US States, Country Codes) and a coworker won't budge on the INT AUTO_INCREMENT as a primary key for all tables.
...
Is there a performance difference between i++ and ++i in C++?
...for ++i
{
this->data += 1;
return *this;
}
Foo Foo::operator++(int ignored_dummy_value) // called for i++
{
Foo tmp(*this); // variable "tmp" cannot be optimized away by the compiler
++(*this);
return tmp;
}
Since the compiler isn't generating code, but just calling an ...
Overriding fields or properties in subclasses
... behavior. You should remember though, that when at runtime the property MyInt is accessed, the derived class has no control on the value returned. The base class by itself is capable of returning this value.
This is how a truly polymorphic implementation of your property might look, allowing the d...
Getting image dimensions without reading the entire file
...static Size GetDimensions(BinaryReader binaryReader)
{
int maxMagicBytesLength = imageFormatDecoders.Keys.OrderByDescending(x => x.Length).First().Length;
byte[] magicBytes = new byte[maxMagicBytesLength];
for (int i = 0; i < maxMagicBytesLength; i...
Any shortcut to initialize all array elements to zero?
...
A default value of 0 for arrays of integral types is guaranteed by the language spec:
Each class variable, instance variable, or array component is initialized with a default value when it is created (§15.9, §15.10) [...] For type int, the default value ...
C# Sortable collection which allows duplicate keys
...TKey : IComparable
{
#region IComparer<TKey> Members
public int Compare(TKey x, TKey y)
{
int result = x.CompareTo(y);
if (result == 0)
return 1; // Handle equality as beeing greater
else
return result;
}
#endregion
}
Y...
Must qualify the allocation with an enclosing instance of type GeoLocation
...GeoLocation outer = new GeoLocation();
Then create instance of class you intended to call, as follows:
service.submit(outer.new ThreadTask(i));
I hope this will resolve your issue;-)
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im...
$(this).serialize() — How to add a value?
...) to get an array from the form data, modify it, and use jQuery.param() to convert it to a url-encoded form. This way, jQuery handles the serialisation of your extra data for you.
var data = $(this).serializeArray(); // convert form to array
data.push({name: "NonFormValue", value: NonFormValue});
$...
How to create JSON string in JavaScript?
...bj = new Object();
obj.name = "Raj";
obj.age = 32;
obj.married = false;
//convert object to json string
var string = JSON.stringify(obj);
//convert string to Json Object
console.log(JSON.parse(string)); // this is your requirement.
...