Having blueprint open in editor decreases performance x2?

Development Platform & Builds Debugging, Optimization, & Profiling
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Originally I thought building was the problem, then saving, now it seems just having the blueprint open in the editor decreases performance by 2X. I have a timer built into the blueprint to start at beginning and stop when processing functions are complete.

Project is basic, and only has this single blueprint. Here are the steps I’ve repeated dozens of times trying to make sense of it:

  1. Open project, blueprint not open (in edit mode) in editor, press play. avg ms: 800
  2. Build project, press play: avg ms: 800
  3. Click Save All, press play: avg ms: 800
  4. Click edit blueprint to open in editor, make no changes, press play: ms: 1600+
  5. Close blueprint in editor, press play: ms: still 1600+

So, just having the blueprint open in the editor will automatically make the project run 2x slower in development?
Is it just me, or does this seem really odd?

No log errors, no tick events, nothing in construction script, event BP as shown is clean. Are there some project or editor settings I’m overlooking?

Updated project to 4.18 to rule out a version glitch, no difference. Now I have to go back and determine if all my blueprints are running at half speed under these conditions.

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Machine specs: i7-6700k, gtx1070, 16gb ram, ssd’s…

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Try out profiling:

It’s mainly done for C++ but as you will see name of threads and functions involved it might give you idea which portion of you blueprint code is the culprit

Blueprint runtime is heavy out of it self, it around 10x slower then native code, because of that it is not recommend to do any heavy on tick operations as running blueprint on every frame might hit up performance

You can also use Blueprint nativisation, it converts Blueprint to C++ code (requires you to have VS instlled to build that code), it sometimes buggy and not everything is supported so some things my not work for you but may speed up things for you. Problem here is it only nativise code on packageing so you would still need to use slow code in editor.

https://docs.unrealengine.com/latest/INT/Engine/Blueprints/TechnicalGuide/NativizingBlueprints/

But i really recomad you to optimize your blueprints before using it, messy blueprints gonna make messy C++ code :stuck_out_tongue: There also chance that your issue is not even blueprint performerce related and nativisation won’t fix it.

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and it is the best optimization session that Epic has made Video Link