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++i vs i++ which one is faster and why?
Автор tawhidmonowar, история, 3 года назад, По-английски

In programming, “++i” and “i++” are both used to increment the value of a variable by 1, but the difference is in the order in which the increment operation and the use of the variable occur.

When it comes to the difference between “++i” and “i++”, it’s important to understand how each operator works. “++i” is known as the pre-increment operator, which increments the value of ‘i’ immediately and returns the incremented value. On the other hand, “i++” is known as the post-increment operator, which increments the value of ‘i’ but returns the original value that ‘i’ held before being incremented.

Example:

Code

In terms of performance, “++i” is sometimes faster than “i++” and is never slower than "i++". For intrinsic types like int, it doesn’t matter: “++i” and “i++” are the same speed. However, for class types like iterators, “++i” very well might be faster than “i++” since the latter might make a copy of the this object.

In conclusion, while there may be some performance differences between “++i” and “i++”, it’s generally recommended to use “++i” unless you specifically want the postfix semantics.

I hope this information will be helpful to you.

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3 года назад, скрыть # |
 
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Based

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Remember that, most of the time compiler is smarter than you think.

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In many cases, the compiler will optimize i++ to ++i, so it's not necessary to use ++i everywhere in code. I personally just use post-increment because that's how I like my code to look.

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If using this to speed up your code by 1 nanoseconds matter so much I recommend just finding a better approach

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Good entry but I will try to more elaborate on "why"

Foo& Foo::operator++()   // called 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;
}

i++ is usually slower due to the fact that it creates a new temporary object for its operation whereas ++i works directly on the object

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