Benchmark: Powers of two - MeasureThat.net

Tests:

for with if
var j = "MSKU947765"; var s = 0; var r = [1,2,4,8,16,32,64,128,256,512]; for (var e=0;e<10;e++) { if (e<4) { var c = j.charCodeAt(e)-55; s+=(Math.floor(c/10.2)+c)*r[e]; } else { s+=Number(j.charAt(e))*r[e]; }; }; var d = s % 11 % 10; return d;
2x for
var j = "MSKU947765"; var s = 0; var r = [1,2,4,8,16,32,64,128,256,512]; for (var e=0;e<4;e++) { var c = j.charCodeAt(e)-55; s+=(Math.floor(c/10.2)+c)*r[e]; }; for (var f=0;f<6;f++){ s+=Number(j.charAt(e))*r[e]; }; var d = s % 11 % 10; return d;
2x for charcode-48
var j = "MSKU947765"; var s = 0; var r = [1,2,4,8,16,32,64,128,256,512]; for (var e=0;e<4;e++) { var c = j.charCodeAt(e)-55; s+=(Math.floor(c/10.2)+c)*r[e]; }; for (var f=0;f<6;f++){ s+=(j.charCodeAt(e)-48)*r[e]; }; var d = s % 11 % 10; return d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for with if
2x for
2x for charcode-48

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Overview**

The provided benchmark measures performance differences in three test cases, each involving a different approach to processing a string variable "j" and calculating the result "d". The tests aim to determine whether processing the string as we go (in a loop) or in advance (outside of a loop) yields better performance.

**Script Preparation Code**

The script preparation code is not provided, which suggests that MeasureThat.net is relying on the JavaScript engine's internal optimizations and caching mechanisms. In other words, the benchmark assumes that the JavaScript engine has already compiled and optimized the input code for each test case.

**Individual Test Cases**

There are three test cases:

1. **"for with if"**
In this test case, we see a traditional `for` loop (with an initial value) followed by an `if` statement inside the loop. This approach can lead to slower performance due to:
	* Additional overhead for the `if` statement
	* Potential cache misses due to the loop variable changing values
2. **"2x for"**
This test case uses two separate `for` loops: one for each iteration of the string processing. This approach can lead to faster performance due to:
	* Reduced overhead from the `if` statement
	* Improved caching, as the loop variables are constant
3. **"2x for charcode-48"**
This test case is similar to "2x for", but uses a different method to process the string characters (`j.charCodeAt(e)-48`) instead of relying on the `charCodeAt()` method directly. This approach can lead to faster performance due to:
	* Avoiding potential cache misses caused by the `charCodeAt()` method

**Library and Purpose**

MeasureThat.net relies on various JavaScript libraries and engines, including:

1. **Gecko**: A JavaScript engine developed by Mozilla, used in Firefox browsers.
2. **V8**: The JavaScript engine used in Google Chrome.

These engines provide built-in optimizations and caching mechanisms that are exploited by MeasureThat.net's benchmarking framework.

**Special JS Feature: String CharCodeAt()**

The `charCodeAt()` method is a built-in JavaScript method that returns the Unicode code point of a character at a specified index. This method can be affected by cache misses, as it requires accessing memory locations outside the current function call stack. MeasureThat.net's benchmarking framework accounts for this potential overhead in its test cases.

**Alternatives and Considerations**

Alternative approaches to measure performance differences:

1. **Manual Loop Optimization**: Writing optimized loops using assembly-like syntax (e.g., SSE/AVX instructions) can lead to better performance.
2. **Just-In-Time (JIT) Compilation**: Some JavaScript engines, like V8, provide JIT compilation capabilities that allow for dynamic optimization of code.
3. **Parallel Processing**: Using multiple CPU cores or threads to execute the test case in parallel can lead to significant performance gains.

When writing benchmarks, consider factors such as:

1. **Cache Efficiency**: Minimize cache misses by using techniques like loop unrolling and register blocking.
2. **Memory Access Patterns**: Optimize memory access patterns to reduce false sharing and improve data locality.
3. **Branch Prediction**: Use branch prediction techniques, like speculative execution, to minimize branch mispredictions.

Keep in mind that JavaScript engines are constantly evolving, and optimizations may change from version to version. MeasureThat.net's benchmarking framework provides a useful starting point for understanding performance differences in specific test cases.

Latest run results:

Run details: (Test run date: 7 years ago)

User agent: Mozilla/5.0 (Windows NT 6.1; rv:53.0) Gecko/20100101 Firefox/53.0

Browser/OS: Firefox 53 on Windows 7

View result in a separate tab

Test name	Executions per second
for with if	3464956.2 Ops/sec
2x for	3691410.0 Ops/sec
2x for charcode-48	20271778.0 Ops/sec

Related benchmarks:

Powers of two (version: 0)

If they should be written in an array or in the loop as we go

Comparing performance of: for with if vs 2x for vs 2x for charcode-48

Created: 7 years ago by: Guest

Jump to the latest result

for with if

2x for

2x for charcode-48

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):