Surge

Swift + Accelerate

Accelerate is a framework that provides high-performance functions for matrix math, digital signal processing, and image manipulation. It harnesses SIMD instructions available in modern CPUs to significantly improve performance of certain calculations.

Because of its relative obscurity and inconvenient APIs, Accelerate is not commonly used by developers... which is a shame, since many applications could benefit from these performance optimizations.

Surge aims to bring Accelerate to the mainstream, making it as easy (and nearly as fast, in most cases) to perform computation over a set of numbers as for a single member.

Though, keep in mind: Accelerate is not a silver bullet. Under certain conditions, such as performing simple calculations over a small data set, Accelerate can be out-performed by conventional algorithms. Always benchmark to determine the performance characteristics of each potential approach.

Curious about the name Surge? Back in the mid 90's, Apple, IBM, and Motorola teamed up to create AltiVec (a.k.a the Velocity Engine), which provided a SIMD instruction set for the PowerPC architecture. When Apple made the switch to Intel CPUs, AltiVec was ported to the x86 architecture and rechristened Accelerate. The derivative of Accelerate (and second derivative of Velocity) is known as either jerk, jolt, surge, or lurch, hence the name of this library.

Performance

Initial benchmarks on iOS devices and the iOS simulator indicate significant performance improvements over a conventional Swift implementation.

import Surge

let numbers: [Double] = ... // 1000000 Elements
var sum: Double = 0.0

// Naïve Swift Implementation
sum = reduce(numbers, 0.0, +) // Time: 5.700 sec (2% STDEV)

// Surge Implementation
sum = Surge.sum(numbers) // Time: 0.001 sec (17% STDEV)

n	Swift	Surge	Δ
100	0.001 sec	0.000 sec	?
10000	0.058 sec	0.000 sec	?
1000000	5.700 sec	0.001 sec	5700x
100000000	?	0.087 sec	?

It was difficult to make a reasonable performance comparison between the two implementations, as the Accelerate-backed function did not register >= 1 msec runtime until n = 1000000. At n = 100000000, the naïve implementation effectively timed out after several minutes.

Surge's performance characteristics have not yet been thoroughly evaluated, though initial benchmarks show incredible promise. Further investigation is definitely warranted.

Installation

The infrastructure and best practices for distributing Swift libraries are currently in flux during this beta period of Swift & Xcode. In the meantime, you can add Surge as a git submodule, drag the Surge.xcodeproj file into your Xcode project, and add Surge.framework as a dependency for your target.

Inventory

Surge functions are named according to their corresponding "Math.h" functions, where applicable (omitting f and d affixes, since type information is communicated and enforced by the language's type system).

Arithmetic

sum
add
mul
div
mod
remainder
sqrt

Auxilliary

abs
ceil
copysign
floor
rec
round
trunc

Exponential

exp
exp2
log
log2
log10
logb

Hyperbolic

sinh
cosh
tanh
asinh
acosh
atanh

Power

pow

Trigonometric

sincos
sin
cos
tan
asin
acos
atan
rad2deg
deg2rad

Usage

Computing Sum of `[Double]`

import Surge

let n = [1.0, 2.0, 3.0, 4.0, 5.0]
let sum = Surge.sum(n) // 15.0

Computing Product of Two `[Double]`s

import Surge

let a = [1.0, 3.0, 5.0, 7.0]
let b = [2.0, 4.0, 6.0, 8.0]

let product = Surge.mul(a, b) // [2.0, 12.0, 30.0, 56.0]

Contact

Mattt Thompson

License

Surge is available under the MIT license. See the LICENSE file for more info.

iBeacons/Surge