Problems with treebuild -- setting the TREE_NUM_BEFORE_NODESPLIT

From: Weiguang Cui <cuiweiguang_at_gmail.com>
Date: Sat, 21 Aug 2021 09:10:39 +0100

Dear all,

I recently met another problem with the 2048^3, 200 mpc/h run.

treebuild in SUBFIND requires a higher value for TREE_NUM_BEFORE_NODESPLIT:
==========================================================
SUBFIND: We now execute a parallel version of SUBFIND.
SUBFIND: Previous subhalo catalogue had approximately a size 2.42768e+09,
and the summed squared subhalo size was 8.42698e+16
SUBFIND: Number of FOF halos treated with collective SubFind algorithm = 1
SUBFIND: Number of processors used in different partitions for the
collective SubFind code = 2
SUBFIND: (The adopted size-limit for the collective algorithm was 9631634
particles, for threshold size factor 0.6)
SUBFIND: The other 10021349 FOF halos are treated in parallel with serial
code
SUBFIND: subfind_distribute_groups() took 0.044379 sec
SUBFIND: particle balance=1.10537
SUBFIND: subfind_exchange() took 30.2562 sec
SUBFIND: particle balance for processing=1
SUBFIND: root-task=0: Collectively doing halo 0 of length 10426033 on 2
 processors.
SUBFIND: subdomain decomposition took 8.54527 sec
SUBFIND: serial subfind subdomain decomposition took 6.0162 sec
SUBFIND: root-task=0: total number of subhalo coll_candidates=1454
SUBFIND: root-task=0: number of subhalo candidates small enough to be done
with one cpu: 1453. (Largest size 81455)
Code termination on task=0, function treebuild_insert_group_of_points(),
file src/tree/tree.cc, line 489: It appears we have reached the bottom of
the tree because there are more than TREE_NUM_BEFORE_NODESPLIT=16 particles
in the smallest tree node representable for BITS_FOR_POSITIONS=64.
Either eliminate the particles at (nearly) indentical coordinates, increase
the setting for TREE_NUM_BEFORE_NODESPLIT, or possibly enlarge
BITS_FOR_POSITIONS if you have really not enough dynamic range
==============================================

But, if I increase the TREE_NUM_BEFORE_NODESPLIT to 64, FMM seems not
working:
=============================================================
Sync-Point 19835, Time: 0.750591, Redshift: 0.332284, Systemstep:
5.27389e-05, Dloga: 7.02657e-05, Nsync-grv: 31415, Nsync-hyd:
 0
ACCEL: Start tree gravity force computation... (31415 particles)
TREE: Full tree construction for all particles. (presently
allocated=7626.51 MB)
GRAVTREE: Tree construction done. took 13.4471 sec <numnodes>=206492
 NTopnodes=115433 NTopleaves=101004 tree-build-scalability=0.441627
FMM: Begin tree force. timebin=13 (presently allocated=0.5 MB)
Code termination on task=0, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=887, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=40, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=888, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=889, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=3, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=890, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=6, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=891, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=9, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=892, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=893, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=894, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
Code termination on task=20, function gravity_fmm(), file src/fmm/fmm.cc,
line 1879: Can't even process a single particle
======================================

I don't think fine-tuning the value for TREE_NUM_BEFORE_NODESPLIT is a
solution.
I can try to use BITS_FOR_POSITIONS=128 by setting POSITIONS_IN_128BIT, but
I am afraid that the code may not be able to run from restart files.
Any suggestions?
Many thanks.

Best,
Weiguang

-------------------------------------------
https://weiguangcui.github.io/
Received on 2021-08-21 10:11:22

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