Benchmark: pre-decrement vs post-decrement vs assignment operator

Script Preparation code:

let i = 100;

Tests:

pre-decrement
--i
post-decrement
i--
addition assignment operator
i -= 1
operation minus
i = i - 1

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
pre-decrement
post-decrement
addition assignment operator
operation minus

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 15_6_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.6.1 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 15 on iOS 15.6.1

View result in a separate tab

Test name	Executions per second
pre-decrement	364837792.0 Ops/sec
post-decrement	135248304.0 Ops/sec
addition assignment operator	131917544.0 Ops/sec
operation minus	131937752.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):

LLMs can make mistakes. Check important info.

I'll provide an in-depth explanation of the benchmark, its options, pros and cons, and other considerations.

**Benchmark Overview**

The benchmark tests four different approaches to decrementing a variable `i`:

1. Pre-decrement (`--i`)
2. Post-decrement (`i--`)
3. Addition assignment operator (`i -= 1`)
4. Explicit subtraction operator (`i = i - 1`)

**Library Used**

No specific library is used in this benchmark.

**Special JavaScript Features or Syntax**

The `addition assignment operator` (`i -= 1`) uses a special syntax in JavaScript called the "additive assignment operator" (also known as the "augmented assignment operator"). This operator allows you to modify a variable by adding, subtracting, multiplying, or dividing it by another value.

**Benchmark Test Cases**

Here's what each test case does:

* `pre-decrement` (`--i`): Decrements the variable `i` using the decrement operator before using its value.
* `post-decrement` (`i--`): Uses the value of `i` after decrementing it, effectively "removing" the old value from the variable.
* `addition assignment operator` (`i -= 1`): Adds `-1` to `i`, modifying it by subtracting 1.
* `operation minus` (`i = i - 1`): Explicitly calculates the subtraction of 1 from `i` and assigns the result back to `i`.

**Options Compared**

The benchmark compares four different approaches:

* **Pre-decrement**: Decrements `i` before using its value.
* **Post-decrement**: Uses `i`'s value after decrementing it.
* **Addition assignment operator**: Modifies `i` by adding `-1`, effectively subtracting 1.
* **Explicit subtraction operator**: Calculates the subtraction of 1 from `i` explicitly.

**Pros and Cons**

Here are some pros and cons for each approach:

* **Pre-decrement (`--i`)**
	+ Pros: Can be more efficient, as it avoids creating a temporary value for subtraction.
	+ Cons: May be less intuitive or readable, especially in complex expressions.
* **Post-decrement (`i--`)**
	+ Pros: More explicit and easier to read, as the intent is clear.
	+ Cons: May create a temporary value during the decrement operation.
* **Addition assignment operator (`i -= 1`)**:
	+ Pros: Efficient and concise, as it modifies `i` directly.
	+ Cons: May be less readable or intuitive for those unfamiliar with additive assignment operators.
* **Explicit subtraction operator (`i = i - 1`)**
	+ Pros: Clear and explicit, as the intent is obvious.
	+ Cons: May be less efficient due to creating a temporary value.

**Other Considerations**

Keep in mind that:

* The `addition assignment operator` can also be used with other operators, such as multiplication (`i *= 2`) or division (`i /= 2`).
* In modern JavaScript engines, the compiler often optimizes expressions involving additive assignment operators, making them comparable to pre- and post-decrement approaches.
* This benchmark only measures the performance of these four specific decrement operations. Other factors, like memory allocation or garbage collection, may also impact overall system performance.

**Alternatives**

Other alternatives for decrementing a variable could include:

* Using a loop with `i++` ( incrementing `i` instead)
* Utilizing a different data structure, such as an array or a linked list
* Employing a different programming paradigm, like functional programming

However, these alternatives are not directly comparable to the four options tested in this benchmark.

Related benchmarks:

pre-decrement vs post-decrement vs assignment operator (version: 0)

Comparing performance of: pre-decrement vs post-decrement vs addition assignment operator vs operation minus

Created: 3 years ago by: Guest

Jump to the latest result

pre-decrement

post-decrement

addition assignment operator

operation minus

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):