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0.1.0 SparseArray
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‎libraries/SparseArray/.arduino-ci.yml‎

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compile:
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# Choosing to run compilation tests on 2 different Arduino platforms
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platforms:
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- uno
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# - due
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# - zero
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# - leonardo
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- m4
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- esp32
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- esp8266
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# - mega2560
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libraries:
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- "SHT85"

‎libraries/SparseArray/.github/workflows/arduino-lint.yml‎

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name: Arduino-lint
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on: [push, pull_request]
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jobs:
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lint:
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v2
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- uses: arduino/arduino-lint-action@v1
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with:
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library-manager: update
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compliance: strict

‎libraries/SparseArray/.github/workflows/arduino_test_runner.yml‎

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---
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name: Arduino CI
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on: [push, pull_request]
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jobs:
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runTest:
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v2
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- uses: ruby/setup-ruby@v1
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with:
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ruby-version: 2.6
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- run: |
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gem install arduino_ci
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arduino_ci.rb

‎libraries/SparseArray/.github/workflows/jsoncheck.yml‎

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name: JSON check
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on:
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push:
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paths:
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- '**.json'
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pull_request:
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jobs:
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test:
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v2
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- name: json-syntax-check
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uses: limitusus/json-syntax-check@v1
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with:
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pattern: "\\.json$"
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‎libraries/SparseArray/LICENSE‎

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MIT License
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Copyright (c) 2022-2022 Rob Tillaart
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.

‎libraries/SparseArray/README.md‎

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[![Arduino CI](https://github.com/RobTillaart/SparseArray/workflows/Arduino%20CI/badge.svg)](https://github.com/marketplace/actions/arduino_ci)
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[![Arduino-lint](https://github.com/RobTillaart/SparseArray/actions/workflows/arduino-lint.yml/badge.svg)](https://github.com/RobTillaart/SparseArray/actions/workflows/arduino-lint.yml)
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[![JSON check](https://github.com/RobTillaart/SparseArray/actions/workflows/jsoncheck.yml/badge.svg)](https://github.com/RobTillaart/SparseArray/actions/workflows/jsoncheck.yml)
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[![License: MIT](https://img.shields.io/badge/license-MIT-green.svg)](https://github.com/RobTillaart/SparseArray/blob/master/LICENSE)
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[![GitHub release](https://img.shields.io/github/release/RobTillaart/SparseArray.svg?maxAge=3600)](https://github.com/RobTillaart/SparseArray/releases)
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# SparseArray
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Arduino library for sparse arrays of floats.
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TODO REDO DOCUMENTATION.
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## Description
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SparseArray is an **experimental** library to implement a one
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dimensional sparse array of floats (a.k.a. vector) on an Arduino.
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A sparse array is a mn array with mostly zeros and a low percentage
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non-zero values.
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The purpose of this library is efficient storage in memory.
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The maximum array that can be represented is 65535 elements
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with a theoretical maximum of 65535 non-zero elements.
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(although that does not make sense due to overhead)
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In practice the library limits this to 1000 non-zero elements.
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Note: 255 elements would still fit in an UNO's 2K memory.
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Relates to:
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- https://github.com/RobTillaart/SparseMatrix
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- https://github.com/RobTillaart/distanceTable
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Note: this library is derived from SparseMatrix.
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#### Implementation
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The implementation is based on 2 arrays holding ``` x, value```
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where value is float, and x is an uint16_t.
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That are 6 bytes per element.
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The number of elements that the sparse array object can hold are
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given as parameter to the constructor.
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If the space cannot be allocated the size is set to zero.
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In the future other data types should be possible.
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#### Performance
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The elements are not kept sorted or indexed so optimizations might be
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possible but are not investigated yet.
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There is however a test sketch to monitor the performance of
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the most important functions.
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Accessing elements internally is done with a linear search,
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which becomes (much) slower if the number of elements is increasing.
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This means that although in theory there can be 65535 elements,
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in practice a few 100 can already become annoyingly slow.
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To keep performance a bit the library has a limit build in.
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Check the .h file for **SPARSEARRAY_MAX_SIZE 1000**
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## Interface
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```cpp
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#include "SparseArray.h"
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```
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### Constructor + meta
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- **SparseArray(uint16_t size)** constructor.
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Parameter is the maximum number of elements in the sparse array.
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Note this number is limited to **SPARSEARRAY_MAX_SIZE 1000**.
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If the space requested cannot be allocated size will be set to 0.
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- **uint16_t size()** maximum number of elements.
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If this is zero, a problem occurred with allocation happened.
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- **uint16_t count()** current number of elements in the array.
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Should be between 0 and size.
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- **float sum()** sum of all elements ( != 0 ) in the array.
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- **void clear()** resets the array to all zero's again.
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### Access
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- **bool set(uint16_t x, float value)** gives an element in the array a value.
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If the value is set to zero, it is removed from the internal store.
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Returns false if the internal store is full, true otherwise.
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- **float get(uint16_t x)** returns a value from the array.
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- **bool add(uint16_t x, float value)** adds value to an element in the array.
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If needed a new internal element is created.
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If the sum is zero, the element is removed from the internal store.
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Returns false if the internal store is full, true otherwise.
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- **void boundingSegment(uint16_t &minX, uint16_t &maxX)**
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Returns the bounding box in which all values != 0 are located.
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This can be useful for printing or processing the non zero elements.
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## Future
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- documentation
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- test
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- keep in sync with SparseMatrix where possible
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- merge into one class hierarchy?
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- dump should be in the class?
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- or as static function...
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- stream as param dump(Stream str, ...
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#### ideas
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- array { uint32_t, float }; for logging millis/micros + measurement
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delta coding of time stamp? if it fit in 16 bit?
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=> sounds like a class on its own.
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‎libraries/SparseArray/SparseArray.cpp‎

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//
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// FILE: SparseArray.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.0
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// DATE: 2022-07-17
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// PURPOSE: Arduino library for sparse arrays of floats
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// URL: https://github.com/RobTillaart/SparseArray
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//
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// HISTORY:
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// 0.1.0 2022-07-17 initial version
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// derives from SparseMatrix
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#include "SparseArray.h"
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SparseArray::SparseArray(uint16_t sz)
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{
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_count = 0;
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_size = sz;
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if ( _size > SPARSEARRAY_MAX_SIZE)
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{
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_size = SPARSEARRAY_MAX_SIZE;
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}
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_x = (uint16_t *) malloc(sz * sizeof(uint16_t));
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_value = (float *) malloc(sz * sizeof(float));
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// catch malloc error
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if (_x && _value) return;
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// if malloc error set size to zero.
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_size = 0;
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}
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SparseArray::~SparseArray()
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{
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if (_x) free(_x);
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if (_value) free(_value);
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}
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uint16_t SparseArray::size()
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{
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return _size;
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}
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uint16_t SparseArray::count()
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{
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return _count;
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}
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void SparseArray::clear()
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{
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_count = 0;
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}
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float SparseArray::sum()
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{
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float _sum = 0;
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for (uint16_t i = 0; i < _count; i++)
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{
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_sum += _value[i];
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}
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return _sum;
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}
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bool SparseArray::set(uint16_t x, float value)
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{
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int32_t pos = findPos(x);
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// existing element
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if (pos > -1)
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{
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_value[pos] = value;
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if (_value[pos] == 0.0) removeElement(pos);
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return true;
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}
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// does not exist => new element ?
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return newElement(x, value);
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}
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bool SparseArray::add(uint16_t x, float value)
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{
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int32_t pos = findPos(x);
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// existing element
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if (pos > -1)
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{
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_value[pos] += value;
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if (_value[pos] == 0.0) removeElement(pos);
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return true;
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}
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// does not exist => new element ?
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return newElement(x, value);
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}
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float SparseArray::get(uint16_t x)
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{
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int32_t pos = findPos(x);
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if (pos > -1)
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{
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return _value[pos];
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}
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return 0;
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}
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void SparseArray::boundingSegment(uint16_t &minX, uint16_t &maxX)
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{
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uint16_t _minx = 65535, _maxx = 0;
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for (uint16_t i = 0; i < _count; i++)
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{
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if (_x[i] < _minx) _minx = _x[i];
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if (_x[i] > _maxx) _maxx = _x[i];
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}
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minX = _minx;
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maxX = _maxx;
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}
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//////////////////////////////////////////////////////
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//
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// PRIVATE
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//
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int32_t SparseArray::findPos(uint16_t x)
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{
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// linear search - not optimized.
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for (uint16_t i = 0; i < _count; i++)
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{
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if (_x[i] == x)
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{
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return (int32_t)i;
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}
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}
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return -1;
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}
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void SparseArray::removeElement(uint16_t pos)
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{
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_count--;
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// move last element
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// efficiency (keep sorted) is no requirement.
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if (pos == _count) return;
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_x[pos] = _x[_count];
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_value[pos] = _value[_count];
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}
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bool SparseArray::newElement(uint16_t x, float value)
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{
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if (value == 0.0) return true;
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if (_count >= _size) return false;
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_x[_count] = x;
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_value[_count] = value;
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_count++;
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return true;
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}
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// -- END OF FILE --
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