Add checkbox, use last GI solution

[vraypixel]

Add a checkbox to quickly save and use the last calculated GI maps from memory for quick tweak renders.

[Lehm_2001]

You can already do this. The first time your render simply check the auto save checkbox and specify a location. Then check 'switch to saved map'. At the end of your render it will switch the mode to from file and use your saved map. That works for both LC and IR but you have to set them up separately.