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Bricscad BIM laggy when closing files ? (Giving RAM back)

I am talking about Windows Version of Bricscad on Windows 10 20H2.
(Ryzen 3950X, NVme SSD, 64 GB DDR4, RX6800 16 GB)

I access and save my Files from a "Server" Drive in LAN.
1 GBit LAN, external Thunderbold enclosure, standard SATA 1 TB SSD
on a M1 Mac Mini.

OK, saving large Files from Bricscad is pretty slow,
but that could be Firewall/Network/Mac vs PC issues.
(No noticeable Problems from Vectorworks or other Apps though)

And for reasonable DWG File Sizes like up to 10-30 MB it QLSAVE seems quite ok.
t starts to get a bit annoying for 50+ MB DWG files sizes.
But I often have DWG sizes from crappy IFC/Revit Imports up to 980 MB.
Saving will take 5-10+ Minutes.
(No noticeable Problems from Vectorworks or other Apps though)

But what I really don't get ...
When I have Files from 50 MB - 1 TB DWG file size, and Bricscad may need up to 20 GB of RAM ...
When I save such File and wait my 10 minutes to save ...
don't do any changes ....
and just want to close that file from File Tabs ....

It will take at least another 10 Minutes until Bricscad finally just closes the File and frees RAM.

You can Watch Windows Task Manager how Bricscad will cozily free about 200 MB of RAM every second or so.
(No noticeable Problems from Vectorworks with similar (also compressed) File Sizes or other Apps though)

It looks like there is a certain File Size Limit where Bricscad will save and close Files in realtime,
but at something above 30 MB DWG size, it will start to take more time exponentially (?)

Has anybody else noted such behavior,
or is it again just my configuration or potentially AMD GPU ?


  • Hi, Michael,

    maybe it is related ... when using MultiThreading (MTFLAGS > 0), and you have lots of ACIS objects, then releasing that emory consumed by ACIS (in multiple threads) is rather slow, around 3x slower than without using MultiThreading;
    that seems to be an internal ACIS problem, how it releases MT-allocated memory ...
    so at Bricsys side we can't do really much here (except to ask Dassault/Spatial about).

    You might try with MTFLAGS=0, to see if releasing the memory (using same dwg) is faster with MTFLAGS=0 vs. MTFLAGS = 7.

    hope this can explain a bit ?
    many greetings !

  • Hi Torsten,

    sounds reasonable.
    I will try without MT again.

    Forgot to tell the workaround :
    Instead of closing the file,
    you can Exit Bricscad.
    Bricscad will disappear from screen but the BC Thread goes on running
    until it has worked its RAM game.

    But at that time you can open Bricscad again which will use a new Thread
    so you can go on with your work and load new files.

    A bit tedious but definitely faster.

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