Purging cache in Affinity Photo?

[Sofa Gas Rue]

Question:
In Affinity Photo, is it possible to purge the cache / memory, similar to Adobe Photoshop's Purge Cache function?

Issue/situation:
I mostly work with focus stacked product images from the Hasselblad 100 camera which means the files often bounce around 1.5GB ( in full resolution and focus stacked ), and it would be a great help if I can purge the cache as I've notice Affinity Photo hogs up a lot of HDD space ( assuming for caches etc ) and on occasion I'm getting error messages that I am running low on space. 

I try and keep the open documents to a minimum but when doing client review and editing I need to flip between 2 - 10 different documents which is an issue. It has to be noted I do not have a large SSD but it's sufficient for everything else except when Affinity Photo churns through space for caches. 

Tried:
I've searched the forum but not conclusive threads on the matter.

Operating system:
OSX Catalina 10.15.3

Affinity Photo:
Version 1.8.3

Any help or input on this matter is much appreciated, as I'm considering moving from other editors to Affinity Photo.

Thank you in advance.

PS: if this post is in the wrong forum, then please let me know, and I will submit it in another.

[carl123]

No way to purge the cache as far as I am aware

But you may be able to redirect the "cache/scratch" files to another, bigger, drive if you have one spare

There were a couple of threads on this in the past 

[R C-R]

I don't think there is anything equivalent to Photoshop's Purge Cache function in the Affinity apps, mostly because they do not use memory (real & virtual) in the same way. For one thing, Affinity tries to avoid keeping all of a document's data in memory at the same time, for example (as I understand it) by using mipmaps as sort of proxies for full-sized images.

Also, in the Mac OS the amount of memory reserved for the exclusive use of an app (its private memory) is generally much less than its real or total memory use, so even if an Affinity app did have a purge function, it probably would not be able to release as much memory as you might think.

Of course, the real question is what happens if or when whatever could be purged needs to be reused -- if it is frequently needed data then it would be pointless (& probably counterproductive) to dump it.

[Sofa Gas Rue]

On 4/19/2020 at 1:17 PM, carl123 said:

No way to purge the cache as far as I am aware

But you may be able to redirect the "cache/scratch" files to another, bigger, drive if you have one spare

There were a couple of threads on this in the past 

Thanks for the input. I've already thought of having a seperate scratch / temp disc, but it seems to be overkill for this Affinity. The other posts on here I read through did not have a specific solution either.

[Sofa Gas Rue]

On 4/19/2020 at 2:14 PM, R C-R said:

I don't think there is anything equivalent to Photoshop's Purge Cache function in the Affinity apps, mostly because they do not use memory (real & virtual) in the same way. For one thing, Affinity tries to avoid keeping all of a document's data in memory at the same time, for example (as I understand it) by using mipmaps as sort of proxies for full-sized images.

Also, in the Mac OS the amount of memory reserved for the exclusive use of an app (its private memory) is generally much less than its real or total memory use, so even if an Affinity app did have a purge function, it probably would not be able to release as much memory as you might think.

Of course, the real question is what happens if or when whatever could be purged needs to be reused -- if it is frequently needed data then it would be pointless (& probably counterproductive) to dump it.

Hi R C-R,

To be honest I have zero understanding of memory management, and if I understand you correctly you are referring to RAM?
My issue is that I've experience a few times my hard disk almost running out of space when I am working on Affinity Photo, and once I close the application I regain the space. That is why I am assuming there must be cache / temp files created for each document I have open.    

As far as I know the Purge function in Photoshop allows me to 'dump' the data ( history and undos etc ) for each document to free up space, but at my own risk so to speak - which I am fine with and I don't see any issues in doing so if it's me doing it ( it would be a different matter should the application do it on its own )

Alternative to a purge function would be an option to set up a dedicated scratch disk as Carl123 mentioned, again Adobe has that option ( https://helpx.adobe.com/photoshop/using/scratch-disks-preferences.html )

At any rate I will continue to work on fewer documents at the same time and frequently close the application to free up space, though it's a ball to do so.

 

[R C-R]

1 hour ago, Sofa Gas Rue said:

To be honest I have zero understanding of memory management, and if I understand you correctly you are referring to RAM?

No, I am referring both to "real memory" (RAM) and to virtual memory, the memory management technique that enables paging chunks of data between RAM & disk to create a 'virtual memory space' far larger than RAM alone could provide.

As for understanding the details of how it works in the Mac OS, it is well documented but incredibly complicated. See for example this Apple Developer document. It's old, last updated in 2013, but it covers the basic details like backing stores, swapping/paging, VM objects, wired memory, & so on. I do not know of any more approachable, less technical article than that one. Even so, I understand only parts of it, just enough to know that trying to force purging app data from RAM is probably more likely to decrease performance than improve it.

[Lorox]

On 4/22/2020 at 8:23 AM, Sofa Gas Rue said:

Thanks for the input. I've already thought of having a seperate scratch / temp disc, but it seems to be overkill for this Affinity. The other posts on here I read through did not have a specific solution either.

Is there actually an option in the Affinity apps to set a specific volume or disk partition to be the scratch/temp disk? If there is, it certainly has eluded me up to now...

While working with Photoshop I always had set aside a 25–50 GB partition exclusively as a scratch/temp disk for Photoshop. Would be nice to be able to do this for Photo or Desiger as well!

[R C-R]

3 hours ago, Lorox said:

Is there actually an option in the Affinity apps to set a specific volume or disk partition to be the scratch/temp disk?

There is no such option, in part because the Affinity apps do not use dedicated scratch disks like Photoshop does.

Unlike most apps, Photoshop uses its own built-in memory & disk management scheme instead of (or sometimes in addition to) the one built into the OS. It must do this because it tries to keep all document-related data constantly present in its own private memory space, which can easily exceed by several orders of magnitude the actual amount of physical memory (RAM) installed on the computer. (This is why sometimes Photoshop is referred to disparagingly as a "memory hog.")

The Affinity apps do not do this. Not only do they rely exclusively on the memory & disk management scheme built-into the OS, they also use novel techniques like mipmaps to reduce the document's memory 'footprint.'