Excel using 30-40% of CPU after running macro

[BristolJGM]

Has anyone else experienced this/ do people know what the cause is?

I have a large/ complex spreadsheet with lots of VLOOKUPs. I use a macro to produce the spreadsheet from a template (broadly, the macro takes some input data and 'works up' a template based on it).

The first time I run the macro, Excel uses 100% of CPU to calculate the workbook.

I then use the macro to 'calculate' a second workbook. Excel CPU usage then drops and it drops again if I do it with a third workbook.

What is particularly curious is that a near-identical macro run on a very similar template does not produce the same result. Even stranger, the Excel slowdown continues even if I close Excel and open a new instance of it. Excel only speeds up again if I reboot the system.

It seems peculiar that the slowdown can last even after I've closed and reopened Excel. I thought it might be some temporary file or similar - I tried using Disk Cleanup but it didn't help at all.

I can post the macro - I know people will disapprove of it as it includes use of the Select function a lot (and other things). However, a near-identical macro with a similar level of 'Select' use doesn't produce the same result on a near-identical workbook.

Can anyone help?

 

[mrshl9898]

Are the workbooks file sizes similar?

 

[BristolJGM]

Are the workbooks file sizes similar?

The workbook in question is 36MB. The structure of the other one is very similar but it has more data and is 120MB.

 

[BristolJGM]

The workbook in question is 36MB. The structure of the other one is very similar but it has more data and is 120MB.

(In other words - it is actually the smaller workbook that this is happening with).

I was wondering if it was something about the structure of the workbook so I've tried to make it as similar as possible to the other workbook, but with no success.

I can't share the workbooks - they are confidential.

To add to the confusion - the workbook will consistently get 100% CPU usage on my older Microsoft i5 computer (8 cores). On my current computer (AMD 5950x 16 cores) it initially gets 100% CPU usage but this drops after running the macro too often.

 

[mrshl9898]

Frustrating. I was hoping other issues were with main (slower) book... Given the file sizes that's an unexpected result

 

[BristolJGM]

In principle, what could there possibly be that causes a CPU slowdown which endures after Excel has been closed and re-opened?

As in - I open a file, it uses 100% CPU, but eventually drops to 40% for the reasons above. Close Excel, run disk cleanup to remove any temporary files, re-open the exact same file and 40% CPU usage.

Reboot Windows and it goes back to 100%.

And this only happens on an AMD computer rather than an Intel one. Something about how a 16 core AMD computer interacts with Windows compared to an 8 core Intel one?

It is admittedly a complex workbook (can't share it for confidentiality reasons).

 

[mrshl9898]

Bumping in hope someone can help. I haven't had this experience before, if anything when there is alot of strain it just gets worse