Latest 4.0.3
License MIT
Platforms ios 9.0, requires ARC
Dependencies SwiftEventBus
Frameworks Foundation
Authors , , ,

Fog Machine Framework

viewshed on three phones

Fog Machine is an iOS Swift framework for parallel processing. Solve hard problems fast with the Fog Machine framework.

The Fog Machine framework is a research and development effort to harness the computing power of multiple, locally connected iOS devices. By using a mesh-network of mobile devices, parallel processing techniques allows Fog Machine to analyze data and answer complex questions quickly and efficiently. Parallel processing over mesh-networks reduces the overall time to solve problems by taking advantage of shared resources (processors, memory, etc.). The communication relies on a Wi-Fi or Bluetooth chipset and is built on Apple’s Multipeer Connectivity framework.

There are two demo apps provided. The first demo app is a simple text search that uses the Knuth–Morris–Pratt string search algorithm to find a search term within a given text. The second app calculates the viewshed of a position. A viewshed is the geographical area that is visible from a location. It includes all surrounding points in line-of-sight with the location and excludes points that are beyond the horizon or obstructed by terrain and other features. The viewshed app demonstrates the true power and flexibility of the Fog Machine framework.

Fog Machine was developed at the National Geospatial-Intelligence Agency (NGA) in collaboration with BIT Systems. The government has "unlimited rights" and is releasing this software to increase the impact of government investments by providing developers with the opportunity to take things in new directions. The software use, modification, and distribution rights are stipulated within the MIT license.

Installation with CocoaPods

CocoaPods is a dependency manager for Objective-C and Swift. You can install CocoaPods with the following command:

$ gem install cocoapods


To integrate Fog Machine into your Xcode project using CocoaPods, specify it in your Podfile:

source ''
platform :ios, '9.0'

target 'TargetName' do
pod 'FogMachine', '~> 4.0.3'

Then, run the following command:

$ pod install

Build from source

Pull down the latest source:

git clone [email protected]:ngageoint/fog-machine.git

Download the dependencies that Fog Machine needs from CocoaPods:

pod cache clean --all
pod install

Launch xcode and smile, you’re all done:

open FogMachine.xcworkspace


The Fog Machine framework provides a simple lifecycle for your app to use. After extending FMTool, you can immediately start running your tasks in parallel.

// What do I need help with?  How about saying hello?
public class HelloWorldTool : FMTool {
  public override func createWork(node:FMNode, nodeNumber:UInt, numberOfNodes:UInt) -> HelloWorldWork {
    return HelloWorldWork(nodeNumber: nodeNumber)

  public override func processWork(node:FMNode, fromNode:FMNode, work: FMWork) -> HelloWorldResult {
    let helloWorldWork:HelloWorldWork = work as! HelloWorldWork
    print("Hello world, this is node (helloWorldWork.nodeNumber).")
    return HelloWorldResult(didSayHello: true)

  public override func mergeResults(node:FMNode, nodeToResult: [FMNode:FMResult]) -> Void {
    var totalNumberOfHellos:Int = 0
    for (n, result) in nodeToResult {
      let helloWorldResult = result as! HelloWorldResult
      if(helloWorldResult.didSayHello) {
        totalNumberOfHellos += 1
    print("Said hello (totalNumberOfHellos) times.  It's a good day. :)")

// Tell Fog Machine what we need help with

// Look for friends/devices to help me

// Run HelloWorldTool on all the nodes in the Fog Machine mesh-network and say hello to everyone!

Pros & Cons

Parallel processing over a mesh-network reduces the overall time to solve problems by taking advantage of shared resources provided by each peer, such as processors and memory. Some of the pros and cons of using the Fog Machine framework are listed below.


  • Fog Machine allows your applicaiton to easily take advantage of the shared resources like processors, memory, and storage of all the devices in the mesh network which can considerably increase performance. The table below shows how increasing the number of devices in the peer network decreases the overall search time for the FogStringSearch app provided.
# of Devices FogStringSearch Runtime (seconds)
1 42.5
2 33.6
3 32.7
4 30.0
  • The Fog Machine framework uses Apple’s Multipeer Connectivity framework. Multipeer Connectivity is supported across all iOS devices, which means great interoperability within the iOS family.
  • The framework works entirely disconnected. It does not rely on any backend connection like LTE or Wi-Fi.
  • If, for whatever reason, a device in the peer network fails to process its piece of work, that piece of work will automatically get reprocessed on the initiating device. Reprocessing provides transparent flexibility in the network.
  • Although not the primary focus of Fog Machine, the framework allows devices to easily share data within the peer network.


  • The peer network communication relies on Wi-Fi or Bluetooth chipset and may not be reliable enough if your devices are not in close enough proximity to one another.
  • Introducing a considerably slower device (relative to the other devices) to your network could result in worse performance.
    • Example: Consider a peer network with two iPhone 6s and one iPhone 4s. If each peer device has to process the same number of instructions, then the two iPhone 6s will finish considerably faster than the iPhone 4s. After the two iPhone 6s devices finish they will wait idly for the iPhone 4s to finish processing.
    • If using peer devices of varying processing power is a concern, then logic can easily be added to the FMTool’s lifecycle to account for the discrepancy.
  • The communication overhead between devices is based on the size of your FMWork and FMResult. The size of these components are likely small, but in a case where it is necessary to send a very large amount of data between devices, then the increase in communication time could exceed the decrease gained by parallel processing. If this is the case, you will likely need to re-evaluate your design.
  • A peer network is currently limited to 8 devices.


Fog Machine requires iOS 9.0+.

Pull Requests

If you’d like to contribute to this project, please make a pull request. We’ll review the pull request and discuss the changes. All pull request contributions to this project will be released under the MIT license.

Software source code previously released under an open source license and then modified by NGA staff is considered a "joint work" (see 17 USC § 101); it is partially copyrighted, partially public domain, and as a whole is protected by the copyrights of the non-government authors and must be released according to the terms of the original open source license.


Fog Machine makes use of the following open source projects:

Latest podspec

    "name": "FogMachine",
    "version": "4.0.3",
    "summary": "iOS Framework for parallel processing",
    "homepage": "",
    "license": {
        "type": "MIT",
        "file": "LICENSE"
    "authors": {
        "NGA": "",
        "BIT Systems": "",
        "Scott Wiedemann": "[email protected]",
        "Chris Wasko": "[email protected]"
    "social_media_url": "",
    "source": {
        "git": "",
        "tag": "4.0.3"
    "requires_arc": true,
    "platforms": {
        "ios": "9.0"
    "source_files": "FogMachine/FogMachine/**/*.swift",
    "resource_bundles": {
        "FogMachine": [
    "frameworks": "Foundation",
    "dependencies": {
        "SwiftEventBus": [
            "~> 1.1.0"

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