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[NMusers] IMP and parallelisation

From: Dirk Garmann <dirk.garmann_at_bayer.com>
Date: Mon, 19 Sep 2016 17:29:53 +0000

Dear nmusers.
During a popPK analysis using the M3 method and IMP we observed an unexpect=
ed behavior and would be interested if anyone else observed the same and ca=
n provide guidance/explanations.

The IMP produces "strange" results in cases requiring a parallelization.
We observed a general (and strong) trend that with increasing number of n=
odes the OBF increases (!) which in my opinion is unexpected if the number=
 of samples in MC is sufficiently large.

The initial settings have been as follows:
Parse Type 1

$EST METHOD=IMP INTERACTION LAPLACIAN EONLY=0 ISAMPLE=300 NITER=100=
0 CTYPE=3 NOABORT GRD=SN(1,2) NOTHETABOUNDTEST PRINT=1
$EST METHOD=IMP INTERACTION NOABORT GRD=SN(1,2) EONLY=1 ISAMPLE=300=
0 NITER=30 PRINT=1

With 1 node the OBF decreased to ~- 1400
Using 16 nodes the OBF stabilized at ~ 1000
In both cases the OBF does not fluctuate much after 100 interations (monito=
ring of EM step) and seems to be stable (no clear hint for a local minima).
Interestingly the estimated residual error is higher using 1 node. With 16 =
nodes the variability seems to be shifted to the ETAS.

This behavior might be a concern for a covariate analysis using IMP
Our first assumption was that we need to increase iSAMPLE in the EM step, s=
ince a different seed might be used for each node. However even increasing =
ISAMPLE to 3000 in the first step did not change the results much.
My guess is that it points in the direction of how population values are up=
dated, but I am not an expert in the implementation of IMP in NONMEM

We would be highly interested in any guidance and explanation.

Many thanks in advance

Dirk

Freundliche Gre / Best regards,

Dirk Garmann
Head Quantitative Pharmacology


Bayer Pharma Aktiengesellschaft
BPH-DD-CS-CP-QP, Quantitative Pharmacology
Building 0431, 322
51368 Leverkusen, Germany

Tel: +49 202 365577
Fax:
Mobile: +49 175 3109407
E-mail: dirk.garmann_at_bayer.com
Web: http://www.bayer.com


Vorstand: Dieter Weinand, Vorsitzender | Christoph Bertram
Vorsitzender des Aufsichtsrats: Hartmut Klusik
Sitz der Gesellschaft: Berlin | Amtsgericht Charlottenburg, HRB 283 B




Received on Mon Sep 19 2016 - 13:29:53 EDT

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