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#1 2024-05-08 15:12:30
- vkj
- Member
- Registered: 2019-04-10
- Posts: 29
OpenMP doesnt work in latest master branch
Dear developers,
Compiling OpenMolcas with openmp (-DOPENMP=ON) doesn't seem to work. If i launch the a molcas calculation with OMP_NUM_THREADS and MKL_NUM_THREADS > 1, the output still says its using only 1 thread. I have older installations where OpenMP multiple threads worked in both SERIAL and MPI parallelized versions.
I confirmed that i switch to an older tag/v22.06 and compile in exactly the same environment and launch the same calculation I can see multiple threads running as reported in molcas output.
vkj
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#2 2024-05-13 08:48:59
- Ignacio
- Administrator
- From: Uppsala
- Registered: 2015-11-03
- Posts: 1,085
Re: OpenMP doesnt work in latest master branch
Try with MOLCAS_THREADS=X or "pymolcas -nt X"
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#3 2024-05-14 09:24:16
- vkj
- Member
- Registered: 2019-04-10
- Posts: 29
Re: OpenMP doesnt work in latest master branch
I confirm that the MOLCAS_THREADS option WORKS. I can see multiple threads being used as reflected in output and also processor usage monitored with top.
Unfortunately, atleast for my system/setup I cant see any advantages of OMP/MKL multiple threads speedups.
Calculation Information:
Number of basis functions: 444
RICD=ACTIVE
&RASSCF
Symm=1
charge=0
ras1=5
ras2=0
ras3=5
nactel=10 4 4
CIRoot=6 6 1
NOQUNE
THRS=1.0D-08 1.0D-02 1.0D-02
CIROOT=6 6 1
&CASPT2
xmultistate=ALL
IMAG = 0.2
IPEA = 0.0
System Information
2 X Intel(R) Xeon(R) CPU E5-2640 v4 @ 2.40GHz
Memory = 236 GB
Compilation
GCC - 7.3.1
Linear Algebra - MKL from parallelstudio2019 ; Openblas 0.2.20
Timings are given for SEWARD/RASSCF/CASPT2 in the format of :MINUTES/:MINUTES/HOURS:MINUTES
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
SERIAL NPROCS=2;THREADS=1 NPROCS=4;THREADS=1 NPROCS=1;THREADS=2 NPROCS=1;THREADS=4
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Internal :11/:24/07:45 :10/:13/04:58 :08/:07/03:29
OpenBLAS :03/:15/02:54 :03/:11/02:23 :02/:07/02:12 :03/:20/04:51 :03/:16/04:28
MKL :02/:14/02:50 :02/:10/02:07 :01/:06/02:08 :02/:18/03:29 :02/:18/03:44
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Its puzzling that the timings for Openmolcas_v22.06 are different when enabling multiple threads. I dont see speedups but also not so much slowdowns. I checked with ldd the various .exe are linked to proper libraries.
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
NPROCS=1;THREADS=4
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
OpenBLAS :03/:18/02:37
MKL :01/:17/02:35
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Last edited by vkj (2024-05-15 08:06:40)
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