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Fast array processing functions

Project description

Authors: Michael Griffin
Version: 4.1.0 for 2018-11-16
Copyright: 2014 - 2018
License:This document may be distributed under the Apache 2.0 License.
Language:Python 3.5 or later

Introduction

The arrayfunc module provides high speed array processing functions for use with the standard Python array module. These functions are patterned after the functions in the standard Python Itertools and math module together with some additional ones from other sources.

The purpose of these functions is to perform mathematical calculations on arrays faster than using native Python.

See full documentation at: http://arrayfunc.readthedocs.io/en/latest/


Function Summary

The functions fall into several categories.

Filling Arrays

Function Description
count Fill an array with evenly spaced values using a start and step values.
cycle Fill an array with evenly spaced values using a start, stop, and step values, and repeat until the array is filled.
repeat Fill an array with a specified value.

Filtering Arrays

Function Description
afilter Select values from an array based on a boolean criteria.
compress Select values from an array based on another array of boolean values.
dropwhile Select values from an array starting from where a selected criteria fails and proceding to the end.
takewhile Like dropwhile, but starts from the beginning and stops when the criteria fails.

Examining and Searching Arrays

Function Description
findindex Returns the index of the first value in an array to meet the specified criteria.
findindices Searches an array for the array indices which meet the specified criteria and writes the results to a second array. Also returns the number of matches found.

Summarising Arrays

Function Description
aany Returns True if any element in an array meets the selected criteria.
aall Returns True if all element in an array meet the selected criteria.
amax Returns the maximum value in the array.
amin Returns the minimum value in the array.
asum Calculate the arithmetic sum of an array.

Data Conversion

Function Description
convert Convert arrays between data types. The data will be converted into the form required by the output array.

Mathematical operator functions

Function Equivalent to
add x + y
truediv x / y
floordiv x // y
mod x % y
mul x * y
neg -x
pow x**y or math.pow(x, y)
sub x - y
abs_ abs(x)

Comparison operator functions

Function Equivalent to
eq x == y
gt x > y
ge x >= y
lt x < y
le x <= y
ne x != y

Bitwise operator functions

Function Equivalent to
and_ x & y
or_ x | y
xor x ^ y
invert ~x
lshift x << y
rshift x >> y

Power and logarithmic functions

Function Equivalent to
exp math.exp(x)
expm1 math.expm1(x)
log math.log(x)
log10 math.log10(x)
log1p math.log1p(x)
log2 math.log2(x)
sqrt math.sqrt(x)

Hyperbolic functions

Function Equivalent to
acosh math.acosh(x)
asinh math.asinh(x)
atanh math.atanh(x)
cosh math.cosh(x)
sinh math.sinh(x)
tanh math.tanh(x)

Trigonometric functions

Function Equivalent to
acos math.acos(x)
asin math.asin(x)
atan math.atan(x)
atan2 math.atan2(x, y)
cos math.cos(x)
hypot math.hypot(x, y)
sin math.sin(x)
tan math.tan(x)

Angular conversion

Function Equivalent to
degrees math.degrees(x)
radians math.radians(x)

Number-theoretic and representation functions

Function Equivalent to
ceil math.ceil(x)
copysign math.copysign(x, y)
fabs math.fabs(x)
factorial math.factorial(x)
floor math.floor(x)
fmod math.fmod(x, y)
isfinite math.isfinite(x)
isinf math.isinf(x)
isnan math.isnan(x)
ldexp math.ldexp(x, y)
trunc math.trunc(x)

Special functions

Function Equivalent to
erf math.erf(x)
erfc math.erfc(x)
gamma math.gamma(x)
lgamma math.lgamma(x)

Attributes

In addition to functions, a set of attributes are provided representing the platform specific maximum and minimum numerical values for each array type. These attributes are part of the “arraylimits” module.


Supported Array Types

Arrayfunc supports all standard Python 3.x array types.


Performance

Average performance increase on x86_64 Ubuntu with GCC is 100 times faster than native Python. Performance will vary depending on the function, operation, array data type used, and whether overflow checking is enabled, with the performance increase ranging from 50% to 500 times.

Other platforms show similar improvements.

Detailed performance figures are listed in the full documentation.


Platform support

Arrayfunc is written in ‘C’ and uses the standard C libraries to implement the underlying math functions. Arrayfunc has been tested on the following platforms.

OS Bits Compiler Python Version Tested
Ubuntu 18.04 LTS 64 bit GCC 3.6
Ubuntu 18.10 64 bit GCC 3.6
Debian 9 32 bit GCC 3.5
Debian 9 64 bit GCC 3.5
OpenSuse 15 64 bit GCC 3.6
FreeBSD 11 64 bit LLVM 3.5
MS Windows 10 64 bit MS Visual Studio C 2015 3.7
Raspbian (RPi 3) 32 bit GCC 3.5

The Raspbian (RPi 3) tests were conducted on a Raspberry Pi ARM CPU. All others were conducted using VMs running on x86 hardware.


Installation

Please note that this is a Python 3 package. To install using Pip, you will need (with Debian package in brackets):

  • The appropriate C compiler and header files (gcc and build-essential).
  • The Python3 development headers (python3-dev).
  • Pip3 together with the corresponding Setuptools (python3-pip).

example:

# Install from PyPI.
pip3 install arrayfunc
# Install from a local copy of the source package (Linux).
pip3 install --no-index --find-links=. arrayfunc
# Windows seems to use "pip" instead of "pip3" for some reason.
pip install arrayfunc

Release History

  • 4.1.0 - Added isfinite function.
  • 4.0.1 - Repeat upload to synchronise source and Windows binary “wheel”
    version. PyPI was not happy with the previous attempt.
  • 4.0.0 - Major revision with many changes. Amap, starmap, and acalc were
    replaced with new individual functions. This change was made to provides a simpler and more consistent interface which is tailored to the individual function rather than attempting to make one parameter format fit all. The “disovfl” parameter has been named to “matherrors” in order to better reflect that it encompasses more than just integer overflow. Support for the “bytes” type has been removed. The Raspberry Pi has been added as a supported platform.
  • 3.1.0 - Added log2 to amap, amapi, and acalc.
  • 3.0.0 - Changed package format to “Wheel” files. No functional changes.
  • 2.1.1 - Fixed missing header files in PyPI package. No functional changes.
  • 2.0.0 - Many changes. Updated MS Windows support to 3.6 and latest compiler.
    This in turn brought the Windows version up to feature parity with the other versions. Changed supported MS Windows version from 32 bit to 64 bit. Added SIMD support for some functions which provided a significant performance for those affected. Updated supported versions of Debian and FreeBSD to current releases.
  • 1.1.0 - Added support for math constants math.pi and math.e.
  • 1.0.0 - First release.

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