AppleAccelerate.jl

Julia interface to OS X's Accelerate framework
Popularity
14 Stars
Updated Last
5 Months Ago
Started In
November 2014

AppleAccelerate.jl

Build Status

This provides a Julia interface to some of OS X's Accelerate framework. At the moment, the package consists mostly of an interface to the array-oriented functions, which provide a vectorised form of many common mathematical functions, however the package does provide access to several other vectorized operations and more are being added on a regular basis. In general, the performance is significantly better than using standard libm functions, though there does appear to be some reduced accuracy.

The following functions are supported:

  • Rounding: ceil, floor, trunc, round
  • Logarithmic: exp, exp2, expm1, log, log1p, log2, log10
  • Trigonometric: sin, sinpi, cos, cospi, tan, tanpi, asin, acos, atan, atan2, cis
  • Hyperbolic: sinh, cosh, tanh, asinh, acosh, atanh
  • Convolution: conv, xcorr
  • Other: sqrt, copysign, exponent, abs, rem

Note there are some slight differences from behaviour in Base:

  • No DomainErrors are raised, instead NaN values are returned.
  • round breaks ties (values with a fractional part of 0.5) by choosing the nearest even value.
  • exponent returns a floating point value of the same type (instead of an Int).

Some additional functions that are also available:

  • rec(x): reciprocal (1.0 ./ x)
  • rsqrt(x): reciprocal square-root (1.0 ./ sqrt(x))
  • pow(x,y): power (x .^ y in Base)
  • fdiv(x,y): divide (x ./ y in Base)
  • sincos(x): returns (sin(x), cos(x))

Example

To avoid naming conflicts with Base, methods are not exported and so need to be accessed via the namespace:

using AppleAccelerate
using BenchmarkTools
X = randn(1_000_000);
@btime exp.($X); # standard libm function
@btime AppleAccelerate.exp($X); # Accelerate array-oriented function

The @replaceBase macro replaces the relevant Base methods directly

@btime sin.($X); # standard libm function
AppleAccelerate.@replaceBase sin cos tan
@btime sin($X);  # will use AppleAccelerate methods for vectorised operations

X = randn(1_000_000);
Y = fill(3.0, 1_000_000);
@btime $X .^ $Y;
AppleAccelerate.@replaceBase(^, /) # use parenthesised form for infix ops
@btime $X ^ $Y;

Output arrays can be specified as first arguments of the functions suffixed with !:

out = zeros(Float64, 1_000_000)
@btime AppleAccelerate.exp!($out, $X)

Warning: no dimension checks are performed on the ! functions, so ensure your input and output arrays are of the same length.

Operations can be performed in-place by specifying the output array as the input array (e.g. AppleAccelerate.exp!(X,X)). This is not mentioned in the Accelerate docs, but this comment by one of the authors indicates that it is safe.