[isabelle] Any way to deactivate multithreading in Isabelle 2009-1?

Is there any simple way to deactivate multithreading in Isabelle? I'm using Isabelle 2009-1 with PolyML 5.3, and I'm seeing multithreading for the first time.

Multithreading seems to be mildly useful on my desktop machine at work, with cpu usage of 110-150% of one core being reported. On my desktop machine at home, though, it seems to cause random and unrepeatable build failures. More than 5  different attempts to build the HOL image failed 5 different ways, sometimes with a meaningful but unexpected exception being reported and sometimes with no explanation.

I've discovered the way to make progress is to tie up the other cores with useless work. These days I use a busy loop written in 10 lines of C code, although the original discovery involved Unreal Tournament. Interestingly PolyML's CPU usage still peaks at around 120% of one core - it must be getting CPU quota for 2 or 3 threads while my busy loop gets less. Curiously, this does not seem to create a problem, or at least, it's not so likely.

Anyway, is there an environment variable or ML reference I can tweak to disable threading for more reliable builds?


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