[tex-live] strange discrepancy in running time of etex between TL2015 and TL2017

[Reinhard Kotucha]

On 2017-07-26 at 22:00:30 +0200, jfbu wrote:

 > 3. run in this work repertory the test file which I will indicate
 > next via
 > 
 > "time etex testmachin.tex"
 > 
 > - with TL2017
 > 
 > - with TL2015

Dear Jean-Francois,
I get

  TL2017:  computed in 9.27 seconds.
  TL2015:  computed in 9.21 seconds.

No significant difference, but in both cases I get the error message

  ! Undefined control sequence.
  l.31 \ifx\x\Z \message{OK}\else \ERROR
                                        \fi

and thus the return value of "time" isn't usable.  What went wrong?

My system is an AMD 2.4 GHz CPU running Gentoo Linux and TeX binaries
are from tug.org.

I must admit that benchmarks are confusing me ATM.  I've written a
tiny program in several programming languages which does nothing else
than to multiply numbers in nested for-loops.  On my old AMD machine,
luajit was as fast as C.  On my brand-new Intel i7-7700K luajit is
twice as fast as C.  Don't know why.  The CPU clock frequency is
obviously not all that counts.

Regards,
  Reinhard

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