Race condition in rng?

[biddisco]

By chance I notice that the turbulence test fails from time to time. This repeated soak test gives more info

tries=1000; count=0; for i in `seq 1 $tries`; do echo $i; output=`ctest --output-on-failure -R turbulence_tests 2>&1 >> fail.txt`; if [ -z "$output" ]; then count=$(($count+1)); fi; done; echo "$count out of $tries completed successfully"

produces

964 out of 1000 completed successfully

on average it seems to be failing 3.5% of the time. Examining the fail.txt file shows output of the form

Total Test time (real) =   0.01 sec
Test project /home/biddisco/build/sphexa
    Start 30: turbulence_tests
1/1 Test #30: turbulence_tests .................***Failed    0.01 sec
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from Turbulence
[ RUN      ] Turbulence.rngSerialize
/home/biddisco/src/sphexa/sph/test/hydro_turb/rng.cpp:66: Failure
Expected equality of these values:
  originalEngine
    Which is: 42 3107752595 1895908407 3900362577 3030691166 4081230161 2732361568 1361238961 3961642104 867618704 2837705690 3281374275 3928479052 3691474744 3088217429 1769265762 37695088
etc etc etc