[ANSYS Meshing] Mesher uses 100% CPU while writing completed mesh and freezes

jones007 · August 5, 2023, 18:27

On a new install of Ansys 2023 R1 I've run into a pretty consistent problem with mashes over a few million nodes where the Mesher ramps up to 100% CPU usage after it has completed the meshing and is trying to save the mesh. Usually the Mesher window goes black, and in the task manager the Mesher shows up as "not responding." In some cases it will recover after a few seconds to a minute, and then everything is fine. Other times it hangs, and never recovers.

I've been using Ansys for about a decade, and with previous versions I've been able to get meshes of 20 million nodes or so without issue. I'm not sure what is different now.

Any suggestions?

Edit: The above was running on a Core I9 with 64GB RAM. I copied the project over to a machine with Dual Xeon CPUs and 96 GB RAM, and I also get 100% CPU usage during the last moments of the mesh generation, and the Mesher screen goes black for a bit, but so far, the Mesher recovers and I get a valid mesh. For what it's worth, it's a 6-block mesh and the total node count is under 910k.

jones007 · August 8, 2023, 17:12

Does nobody else have this problem? I get it on multiple machines, and it seems to be more problematic with multi-block meshes than with node count. I can have the mesher hang with meshes well under 1 million nodes if there are several blocks. If I mesh one block at a time, sometimes i can get the job done, but if I let it mesh all blocks simultaneously, that's a recipe for disaster. I can make meshes with several million nodes if it's a single block. The actual meshing works fine - it's only after all faces and volumes are complete, when it tries to save the data that it hangs.

Gert-Jan · August 9, 2023, 01:37

Did you ask ANSYS?

I never install R1 releases. Generally these contain bugs, that are corrected in R2 releases. Therefore I solely use R2 releases.
I installed 2023R2 last week. If I observe the same in the coming month, I will let you know.

jones007 · August 9, 2023, 14:06

Thanks, that's good to know. So in general R1 is roughly a Beta version?

Edit: Thanks - that seems to have resolved the problem.

Edit 2: Shoot - not quite resolved. If I have enough blocks and enough nodes. it will still hang with a black screen. However, I found a couple of fixes that seem to help.
1). Generate meshes in smaller groups of blocks at a time, rather than the whole thing. If one block is really large, occasionally this will still hang.
2). If it hangs, find the DSBrowserService.exe process and kill it. Definitely an ad hoc fix, but it seems to work. Mesher returns. You can go back and try (1) to get a complete mesh.

Gert-Jan · August 10, 2023, 02:43

That is good to hear.

I would not say R1-releases are beta versions. Every year ANSYS has a new version which comes with releases R1, R2 and sometimes even R3. And as every software contains bugs, generally speaking R1 contains more bugs than R2 and R3 versions.
Since I don't rely on features in new versions, I can wait for R2 version.

jones007 · August 10, 2023, 12:42

If I had a choice, I would have delayed, as 2022R2 definitely had everything iIneed, but we teach with it, and our IT people already installed 2023R1 on all the student machines.

siw · August 11, 2023, 03:21

Just as another datapoint, I also skip the R1 versions at my work Ansys installations (FEA and CFD) for the same reasons as Gert-Jan said, although I still read each release's Highlights presentations and documents to see the new stuff.

evcelica · August 22, 2023, 14:39

I believe I may have experienced this issue a long time ago, and it was related to RAM. Very large meshes that max out the RAM were problematic, which is why meshing smaller blocks can be helpful. Did you check RAM usage at the time?
I'm not sure if limiting the CPU cores would help, nor how to do it.

August 5, 2023, 18:27	Mesher uses 100% CPU while writing completed mesh and freezes	#1
jones007 New Member Kevin Jones Join Date: Feb 2011 Posts: 17 Rep Power: 15	On a new install of Ansys 2023 R1 I've run into a pretty consistent problem with mashes over a few million nodes where the Mesher ramps up to 100% CPU usage after it has completed the meshing and is trying to save the mesh. Usually the Mesher window goes black, and in the task manager the Mesher shows up as "not responding." In some cases it will recover after a few seconds to a minute, and then everything is fine. Other times it hangs, and never recovers. I've been using Ansys for about a decade, and with previous versions I've been able to get meshes of 20 million nodes or so without issue. I'm not sure what is different now. Any suggestions? Edit: The above was running on a Core I9 with 64GB RAM. I copied the project over to a machine with Dual Xeon CPUs and 96 GB RAM, and I also get 100% CPU usage during the last moments of the mesh generation, and the Mesher screen goes black for a bit, but so far, the Mesher recovers and I get a valid mesh. For what it's worth, it's a 6-block mesh and the total node count is under 910k.

August 9, 2023, 14:06		#4
jones007 New Member Kevin Jones Join Date: Feb 2011 Posts: 17 Rep Power: 15	Thanks, that's good to know. So in general R1 is roughly a Beta version? Edit: Thanks - that seems to have resolved the problem. Edit 2: Shoot - not quite resolved. If I have enough blocks and enough nodes. it will still hang with a black screen. However, I found a couple of fixes that seem to help. 1). Generate meshes in smaller groups of blocks at a time, rather than the whole thing. If one block is really large, occasionally this will still hang. 2). If it hangs, find the DSBrowserService.exe process and kill it. Definitely an ad hoc fix, but it seems to work. Mesher returns. You can go back and try (1) to get a complete mesh. Last edited by jones007; August 10, 2023 at 12:37. Reason: Update

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August 8, 2023, 17:12		#2
jones007 New Member Kevin Jones Join Date: Feb 2011 Posts: 17 Rep Power: 15	Does nobody else have this problem? I get it on multiple machines, and it seems to be more problematic with multi-block meshes than with node count. I can have the mesher hang with meshes well under 1 million nodes if there are several blocks. If I mesh one block at a time, sometimes i can get the job done, but if I let it mesh all blocks simultaneously, that's a recipe for disaster. I can make meshes with several million nodes if it's a single block. The actual meshing works fine - it's only after all faces and volumes are complete, when it tries to save the data that it hangs.

August 9, 2023, 01:37		#3
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	Did you ask ANSYS? I never install R1 releases. Generally these contain bugs, that are corrected in R2 releases. Therefore I solely use R2 releases. I installed 2023R2 last week. If I observe the same in the coming month, I will let you know.

August 10, 2023, 02:43		#5
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	That is good to hear. I would not say R1-releases are beta versions. Every year ANSYS has a new version which comes with releases R1, R2 and sometimes even R3. And as every software contains bugs, generally speaking R1 contains more bugs than R2 and R3 versions. Since I don't rely on features in new versions, I can wait for R2 version.

August 10, 2023, 12:42		#6
jones007 New Member Kevin Jones Join Date: Feb 2011 Posts: 17 Rep Power: 15	If I had a choice, I would have delayed, as 2022R2 definitely had everything iIneed, but we teach with it, and our IT people already installed 2023R1 on all the student machines.

August 11, 2023, 03:21		#7
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 733 Rep Power: 25	Just as another datapoint, I also skip the R1 versions at my work Ansys installations (FEA and CFD) for the same reasons as Gert-Jan said, although I still read each release's Highlights presentations and documents to see the new stuff.

August 22, 2023, 14:39		#8
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,167 Rep Power: 23	I believe I may have experienced this issue a long time ago, and it was related to RAM. Very large meshes that max out the RAM were problematic, which is why meshing smaller blocks can be helpful. Did you check RAM usage at the time? I'm not sure if limiting the CPU cores would help, nor how to do it.