When to use Float32Array instead of Array in JavaScript

Question

When does it make sense to use a Float32Array instead of a standard JavaScript Array for browser applications?

This performance test shows

Answer 1

I would assume that the glMatrix library uses Float32Array because it is primarily used in WebGL-applications, where matrices are represented as Float32Arrays (http://www.khronos.org/registry/webgl/specs/1.0/#5.14.10).

Answer 2

I emailed the developer of glMatrix and my answer below includes his comments (points 2 & 3):

1. Creating a new object is generally quicker with Array than Float32Array. The gain is significant for small arrays, but is less (environment dependent) with larger arrays.

2. Accessing data from a TypedArray (eg. Float32Array) is often faster than from a normal array, which means that most array operations (aside from creating a new object) are faster with TypedArrays.

3. As also stated by @emidander, glMatrix was developed primarily for WebGL, which requires that vectors and matrices be passed as Float32Array. So, for a WebGL application, the potentially costly conversion from Array to Float32Array would need to be included in any performance measurement.

So, not surprisingly, the best choice is application dependent:

• If arrays are generally small, and/or number of operations on them is low so that the constructor time is a significant proportion of the array's lifespan, use Array.

• If code readability is as important as performance, then use Array (i.e. use [], instead of a constructor).

• If arrays are very large and/or are used for many operations, then use a TypedArray.

• For WebGL applications (or other applications that would otherwise require a type conversion), use Float32Array (or other TypedArray).

Answer 3

In today browsers implementation, using Float32Array has impact in both writibility and performance if compared against vanilla Arrays. It seems that even gl-matrix authors agreed that the library need to be refactored to remove Float32Array dependency: https://github.com/toji/gl-matrix/issues/359