Feel slightly messed up after Jeff Lait's OpenCL vs VEX masterclass.
Can't end up without mistakes
In the last example shown - in the second last Wrangle - Houdini points me to the mistake, that I can't fix, cause it looks for me after comparison the same as in the Jeff's example (in my file it's in the last geo node called > OpenCL_smoothing_back_Worksets_groups. I put there a couple of images of Jeff's Wrangles codes too, and it still looks for me the same written. The mistake is something called - “reference to undefined variable i”. Can't understand what does it mean, “i” there underlined with red 
In the files uploaded for the webinar in the Worksets example nodes look too differently for me to compare and find my mistake.
And why two last OpenCL nodes in the Worksets example from the webinar - are called “gauss_seidel” and “jacobi” - is it meaningful for all or he just called them so for own purposes?
Before watching masterclass I decided to think that OpenCL is a function/technology we can switch on in some of the nodes to make everything faster if GPU allows.
But now I think - OpenCL and Kernel are (if in the OpenCL SOP we press to generate Kernel Code) - languages? VEX - for Houdini only, OpenCL - used somewhere outside of Houdini too? And Kernel is something used in both, but it's somehow visible in the OpenCL and not visible in the VEX? If OpenCL is another language - he has own functions? or Kernel has? If it is so why they don't have own pages like VEX, VOPs and looks as just a geometry node O_O
And one more thing about Kernel - in one of the first Entagma's tutorials Moritz explained Kernel as something related to edge detection or for blurring used e.g. in the image editing.
Are these things - the same Kernel doing different things or these are two different Kernels named the same accidentally??
Thanks for any replies or advices! (and for reading)
