# parallelization works only with one kernel

I am using MMA 12.3.1 on Ubuntu 18.04, and my license support parallelization. The default kernel is Local and I create another one named newKernel. when I launch MMA and choose Local to perform some calculation with parallelization it is working fine. Now if I open new notebook and choose newKernal to do different calculation that also includes parallelization I get this error.

"Unable to communicate with closed link \
LinkObject[\!$$\"/usr/local/Wolfram/Mathematica/12.3/Executables/\ wolfram -noinit -subkernel -pacletreadonly -wstp\"$$,125,4]"


Note that If I restart MMA and run the first code with newKernal it is working fine, but when I run the second code on Local I get the same error.

I tried to uninstall MMA and reinstall again and restart my computer but could not get rid of this. any help please?

For a minimal example one can use any simple code with ParallelSum

• Did you try the standard way like ParallelDo, ParalleTry etc without manual kernel creation? Aug 4 at 11:02
• How would that help? and I need tow kernels to do different calculations separately Aug 5 at 7:40
• If separately, then try LaunchKernels[] and ParallelEvaluate[cmd, kernID]. It allows autoconfiguration of sub-kernels. Aug 5 at 8:20
• the problem is that when I LaunchKernels[] in the second notebook it gives the same error mentioned in the question Aug 5 at 11:04
• Forget about manually created kernel. Launch the default Local as master, then launch the needed amount of sub-kernels by LaunchKernels and use the ParallelEvaluate[command, {kernIDs}] in different notebooks just changing the kernID. They will work fully separately if you set the DistributedContexts->None. Aug 6 at 5:33