Issue with Parallel processing

Questions
,
1

Hi,

I’m running Mathematica 12.0 with a license for 8 kernels. Recently when I run a parallel process (typically with Method->“CoarsestGrained”) only 4 of the kernels (sometimes less) are being used when it is clear that much more than half the tasks are left. In the past all 8 would be active. What is going on and how can I get all 8 kernels to be used?

Thank you,
Troy Wahl

2

Hi Troy,

Have you checked the configuration settings as described in this support article? What does the following evaluate to?

Parallelize[Map[{#, $KernelID} &, Range[12]], Method -> "CoarsestGrained"]
3

Hi,

I have checked and Parallel Kernel Configuration (local) reads:

Automatic: 8 kernels
Number of processor cores is 8
“Limit by license availability (8)” is checked
“Use hard limit:16 + -” is checked

The rest in that block is unchecked.

I’ll have to run your test program when my current computation is done (could be a few days).

4

Hi,

I just ran your code and got:

In[30]:= Parallelize[Map[{#, $KernelID} &, Range[12]], 
 Method -> "CoarsestGrained"]

Out[30]= {{1, 1}, {2, 1}, {3, 2}, {4, 2}, {5, 3}, {6, 3}, {7, 4}, {8, 
  4}, {9, 5}, {10, 6}, {11, 7}, {12, 8}}

Which is as it should be, but the things I’m running are huge (functional arrays 100’s wide, and over 30,000 long) yet not all the kernels are involved…