If it does get too hot you may find krun useful:

krun: run command within temperature window
    
The command:
  krun 80 60 make test
will run the subcommand 'make test' while monitoring CPU temperatures;
if at any point the temperature goes above 80C, the subcommand (proces
+s
group) will be suspended until it falls below 60C, then allowed to res
+ume.
[download]

It relies on the 'sensors' library, which IIRC is available for Ubuntu as the lm-sensors package.

Excellent! The page at askubuntu.com provided me the assistance I needed, and the results are promising:

$ sensors
nouveau-pci-0100
Adapter: PCI adapter
GPU core:     +1.20 V  (min =  +1.20 V, max =  +1.32 V)
fan1:           0 RPM
temp1:        +63.0°C  (high = +95.0°C, hyst =  +3.0°C)
                       (crit = +115.0°C, hyst =  +2.0°C)
                       (emerg = +130.0°C, hyst = +10.0°C)

coretemp-isa-0000
Adapter: ISA adapter
Core 0:       +50.0°C  (high = +80.0°C, crit = +100.0°C)
Core 1:       +46.0°C  (high = +80.0°C, crit = +100.0°C)
$
[download]

I just did a complete run, keeping an eagle eye on the temperature of the two cores.

At the start, the temps were 50C+44C. After starting the script with 50 kids, the temperatures climbed to about 80C+77C, by about a third of the way through. The 'high' value was 80C, and the 'critical' value was 100C, so I watched to see if the temperature got significantly closer to 100C -- but they did not.

After the script completed, the temperatures fell back down to a normal range -- 55C+51C within five minutes. So at this point, I'm fairly confident that running with 50 kids is safe for the hardware that I currently have.

Thanks for all your input!

Modern CPUs regulate their own clocks based on temperature, so you can crank it to the max. The question is does the speed drop. Either way that has nothing to do with parrallisation

If each job is purely CPU crunching you shouldn't see any improvement having more kids than you do cores.

we put the PC case on a chair carefully arranged in front of my secondary fridge, placed the harddisk inside the fridge, and turned the fridge to maximum cooling

-- from afoken's coolest recovery

And if your PC gets too hot, just ask afoken for advice. :-)

👁️🍾👍🦟

if your PC gets too hot, just ask afoken for advice

*g*

Having a research center with a good supply of liquid helium in town surely helps. ;-)

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)