View source for Documentation/Nightly/Developers/Tutorials/MigrationGuide/ITK4-to-ITK5

==Transition from ITK4 to ITK5==
This section lists categories of code changes necessary to build Slicer with ITK 5. Each category has a short description, an example error message, a suggested upgrade path, and references to relevant commits.

Referencing this list might be helpful if Slicer extensions requiring updates to be compatible with ITK 5.

Make also sure to read through the [https://github.com/InsightSoftwareConsortium/ITK/blob/master/Documentation/ITK5MigrationGuide.md ITK 5 migration guide].

[https://github.com/InsightSoftwareConsortium/ITK/tree/master/Utilities/ITKv5Preparation Utilities/ITKv5Preparation] directory contains bash scripts which have been used to update ITK to version 5. These scripts can assist with updating external code bases to ITK 5 content and style.

===Upgrading to ITKv5 or keep using ITKv4 GenerateThreadedData===
If the ThreadedGenerateData does not use threadId, change the name of the function to DynamicThreadedGenerateData
Replace:
<pre>
  void ThreadedGenerateData( const OutputRegionType& threadRegion, ThreadIdType threadId )
</pre>
with: 
<pre>
  void DynamicThreadedGenerateData( const OutputRegionType& threadRegion )
</pre>

If you want to keep using the ITKv4 thread system (with ThreadedGenerateData), add to the constructor of your ITK class:
<pre>
  this->DynamicMultiThreadingOff();
</pre>

===itkMultiThreader refactor===

Replace lines like:
<pre>
  #include <itkMultiThreader.h>

  itk::MultiThreader::Pointer ProcessingThreader;
</pre>

with:
<pre>
  #include <itkPlatformMultiThreader.h>

  itk::PlatformMultiThreader::Pointer ProcessingThreader;
</pre>

===SimpleFastMutexLock, FastMutexLock and MutexLock are deprecated===

Instead use <tt>std::mutex</tt> available in C++11

Replace:
<pre>
  #include "itkSimpleFastMutexLock.h"
  #include "itkFastMutexLock.h"
  #include "itkMutexLock.h"

  SimpleFastMutexLock
  FastMutexLock
  MutexLock
</pre>

with:
<pre>
  #include <mutex>

  std::mutex
</pre>