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Meshing -- time and memory
Posted 19 ago 2011, 03:47 GMT-4 Mesh Version 4.2 1 Reply
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Hi Everyone,
I have a reasonably complex geometry over which I want to create a mesh. Just to see what would happen, I selected "extremely coarse mesh" and hit build all. The result was that my computer spend about two hours allocating more and more memory and topped out at about 4.3 GB for Comsol private memory. Since this peak in memory, the memory usage is declining very slowly. About 18 hours after the peak, the memory usage was 3.2 GB.
My computer has 6GB RAM, so the RAM is large enough to fit this mesh. I have an i7 920 chip, which is a quad-core that supports a further division into two virtual cores per core, so effectively an octacore from the software point of view. During this entire computation, the total CPU load was exactly 12.5% all the time. This seems that Comsol is using one of the chips totally and none of the others. My OS is 64-bit Windows 7 Ultimate.
The questions in this are:
1. Why is Comsol using so little CPU power?
2. Why is meshing taking so long?
3. What meaning does it have that the mesh is at first large and then get smaller?
4. What can I do to provide Comsol with the full CPU speed and to hurry up the meshing?
5. If I select something other than "extremely coarse mesh" can I expect to finish in reasonable time, even if I upgrade my RAM?
Thank you!!
I have a reasonably complex geometry over which I want to create a mesh. Just to see what would happen, I selected "extremely coarse mesh" and hit build all. The result was that my computer spend about two hours allocating more and more memory and topped out at about 4.3 GB for Comsol private memory. Since this peak in memory, the memory usage is declining very slowly. About 18 hours after the peak, the memory usage was 3.2 GB.
My computer has 6GB RAM, so the RAM is large enough to fit this mesh. I have an i7 920 chip, which is a quad-core that supports a further division into two virtual cores per core, so effectively an octacore from the software point of view. During this entire computation, the total CPU load was exactly 12.5% all the time. This seems that Comsol is using one of the chips totally and none of the others. My OS is 64-bit Windows 7 Ultimate.
The questions in this are:
1. Why is Comsol using so little CPU power?
2. Why is meshing taking so long?
3. What meaning does it have that the mesh is at first large and then get smaller?
4. What can I do to provide Comsol with the full CPU speed and to hurry up the meshing?
5. If I select something other than "extremely coarse mesh" can I expect to finish in reasonable time, even if I upgrade my RAM?
Thank you!!
1 Reply Last Post 19 ago 2011, 07:44 GMT-4
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Posted:
1 decade ago
Hi
there is no easy reply, there are many and model dependent I would say
1) meshing is from my knowledge a 1 processor job, still today, and I'm by far not sure its so "easy" to parallelise. Not all task can be efficiently parellelised
2) depending on your model, if you do not tell COMSOL in details, and "coarse" is a summary for 5-6 different parameters settings, COMSOL will try to resolve everything, hence easily make a 1-2M element mesh for a slightly complex objects, but where often 99% of the mes details is of no use
My way around is mostly to mesh complex geometries manually, you gain time, if not when meshing at least when solving. But do not forget that meshing is moe an art than a science ;)
--
Good luck
Ivar
there is no easy reply, there are many and model dependent I would say
1) meshing is from my knowledge a 1 processor job, still today, and I'm by far not sure its so "easy" to parallelise. Not all task can be efficiently parellelised
2) depending on your model, if you do not tell COMSOL in details, and "coarse" is a summary for 5-6 different parameters settings, COMSOL will try to resolve everything, hence easily make a 1-2M element mesh for a slightly complex objects, but where often 99% of the mes details is of no use
My way around is mostly to mesh complex geometries manually, you gain time, if not when meshing at least when solving. But do not forget that meshing is moe an art than a science ;)
--
Good luck
Ivar