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[NMusers] freezes during FOCE+I search with nm743 on Linux

From: HUI, Ka Ho <matthew.hui_at_link.cuhk.edu.hk>
Date: Fri, 28 Dec 2018 04:44:56 +0000

Dear NMusers,

Recently we are encountering freezes during FOCE+I searches on our Linux sy=
stem. The version of NONMEM used is 7.4.3. We set $EST PRINT=1 and observ=
ed that for some datasets (we are working on a large number of simulated da=
tasets) the search would halt indefinitely at certain iteration no. without=
 any further progress (so, never terminated). The only file being constantl=
y updated was the .cpu file.

We resorted to strace and observed that at such iteration no., the followin=
g block popped up repeatedly:
wait4(5956, 0x7ffc2e280874, WNOHANG, NULL) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
nanosleep({1, 0}, {1, 0}) = 0
But we are not sure what to do with it.

Other observations:

  * The exact same model file and datafile terminated successfully with n=
m743 on a Windows 10 system.
  * Whenever this problem occured there seemed to be zero gradients going=
 on.
  * We suspected handling of arithmetic errors such as div/0 error and im=
plemented something like this under $ERROR, but it did not resolve the halt=
:
FLAG=0

IF (F.EQ.0) FLAG=1

Y=((1-FLAG)*F+FLAG*0.001)*(1+EPS(1))

  * Supplying lower and upper bounds on relevant theta('s) seems to remov=
e the halt.

We are wondering if this is a bug in the Linux version. Even if convergence=
 cannot be achieved, we think that the search process needs to timeout itse=
lf. Any suggestion?

P.S. Please let me know if an example set of control stream and datafile is=
 desired.

Thanks and regards,
Matthew


Received on Thu Dec 27 2018 - 23:44:56 EST

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