arrayfunc 2.0.0

Fast array processing functions

Authors:

Michael Griffin

Version:

2.0.0 for 2017-06-30

Copyright:

2014 - 2017

License:

This document may be distributed under the Apache 2.0 License.

Language:

Python 3.4 or later

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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 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.

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Functions

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
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.
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.

Operating on Arrays

Function	Description
amap	Apply an operator to each element of an array, together with an optional second parameter (for operators taking two parameters). The results are written to a second array.
amapi	Like amap, but the results are written in place to the input array.
starmap	Like amap, but where a second array acts as the second parameter. The results are written to an output array.
starmapi	Like starmap, but the results are written in place to the first input array.
asum	Calculate the arithmetic sum of an array.
acalc	Calculate arbitrary equations over an array.

Amap and amapi support more than 70 different operations. Starmap and starmapi support more than two dozen different operations. ACalc supports more than 50 operations.

Data Conversion

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

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.

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Supported Array Types

Arrayfunc supports all standard Python 3.x array types, as well as the ‘bytes’ type.

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Performance

Performance will vary depending on the function, operation, array data type used, and whether overflow checking is enabled.

Average performance increase for amap is 80 times faster than native Python. Functions other than amap, starmap, and acalc average is 50 times faster than native Python. However, some functions and operations may be more than 200 to 300 times faster than native Python.

Detailed performance figures are listed in the documentation.

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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 16.04 LTS	64 bit	GCC	3.5
Debian 9	32 bit	GCC	3.5
Debian 9	64 bit	GCC	3.5
FreeBSD 11	64 bit	LLVM	3.5
MS Windows 10	64 bit	MS Visual Studio C 2015	3.6

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Release History

• 1.0.0 - First release.

• 1.1.0 - Added support for math constants math.pi and math.e.

• 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.