Benchmark: for-loop cached variables / access caching + V8 hints

Script Preparation code:

var arr = [31,12321,213,21321,321321,321321,1];
var processFunc = a => a + 1;

Tests:

caching variable (for global)
for (let i = arr.length, tmp; i--;) { processFunc(tmp = arr[i]); processFunc(tmp); processFunc(tmp); };
single access cache
for (let i = arr.length; i--;) { let tmp = arr[i]; processFunc(tmp); processFunc(tmp); processFunc(tmp); };
zero cache - 3x access
for (let i = arr.length; i--;) { processFunc(arr[i]); processFunc(arr[i]); processFunc(arr[i]); };
caching variable (for global) V8 hints
for (let i = arr.length, tmp = 0; i--;) { processFunc(tmp = arr[i]); processFunc(tmp); processFunc(tmp); };

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
caching variable (for global)
single access cache
zero cache - 3x access
caching variable (for global) V8 hints

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.4972.0 Safari/537.36

Browser/OS: Chrome 102 on Windows

View result in a separate tab

Test name	Executions per second
caching variable (for global)	417808.2 Ops/sec
single access cache	411119.2 Ops/sec
zero cache - 3x access	277277.8 Ops/sec
caching variable (for global) V8 hints	409326.5 Ops/sec

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript microbenchmarking test case, specifically designed to compare the performance of different caching strategies in a for-loop-based scenario.

**Benchmark Overview**

The benchmark tests four variations of caching:

1. **Caching variable (for global)**: This approach caches the loop variable `i` in the scope of the function call, allowing the interpreter to reuse it across multiple iterations.
2. **Single access cache**: In this variation, a new local variable `tmp` is created on each iteration, storing the value of `arr[i]`. This allows for caching only the accessed element, not the loop variable itself.
3. **Zero cache - 3x access**: This approach does not cache anything, meaning that on each iteration, the function call will access `arr[i]`, perform the operation, and then return to execute again immediately.
4. **Caching variable (for global) V8 hints**: Similar to the first variation, but with added "V8 hints" which indicate the caching behavior to the JavaScript engine.

**Pros and Cons of Each Approach**

1. **Caching variable (for global)**:
	* Pros: Reuses loop variable across iterations, potentially reducing function call overhead.
	* Cons: May lead to slower performance due to unnecessary caching.
2. **Single access cache**:
	* Pros: Only caches the accessed element, minimizing unnecessary memory usage.
	* Cons: Creates a new local variable on each iteration, increasing function call overhead.
3. **Zero cache - 3x access**:
	* Pros: Avoids caching, reducing potential performance gains from reusing variables.
	* Cons: Accesses `arr[i]` on every iteration, leading to significant function call overhead and slow performance.
4. **Caching variable (for global) V8 hints**:
	* Pros: Combines the benefits of caching with explicit "V8 hints" for better performance guidance.
	* Cons: May not provide noticeable performance improvements if used incorrectly.

**Library Considerations**

The provided benchmark definition does not explicitly mention any libraries. However, some variations rely on implicit library behaviors:

1. **Caching variable (for global)** and **Caching variable (for global) V8 hints**: These approaches assume the JavaScript engine will use caching for the loop variable `i`. The added "V8 hints" in the latter variation explicitly inform the engine about this caching behavior.
2. **Single access cache**: This approach relies on JavaScript's implicit local variable creation and assignment mechanics.

**Special JS Features or Syntax**

The benchmark definition does not include any special JavaScript features or syntax, as it focuses solely on the caching strategies themselves.

**Alternative Approaches**

Other caching strategies that are not tested in this benchmark include:

1. **Registering variables with `V8.register`**: This API allows developers to explicitly register variables for caching, potentially improving performance.
2. **Using compiler-specific optimizations**: Some JavaScript engines provide compiler-specific optimizations or flags that can improve caching behavior.

Keep in mind that these alternative approaches might require additional setup, library integration, or engine-specific configuration, which may not be relevant to this specific benchmarking test case.

Related benchmarks:

for-loop cached variables / access caching + V8 hints (version: 0)

Comparing performance of: caching variable (for global) vs single access cache vs zero cache - 3x access vs caching variable (for global) V8 hints

Created: 2 years ago by: Guest

Jump to the latest result

caching variable (for global)

single access cache

zero cache - 3x access

caching variable (for global) V8 hints

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):