From: John Stone (
Date: Thu Dec 17 2020 - 09:43:05 CST

  I tested this carefully last night and it seems that the issue is
caused by differences in how different versions of the Microsoft compilers
handle the state() system call on large files. With the new compilers
operating in 64-bit mode, stat() returns a failure on large files.

The DCD plugin previously used stat() to ascertain the size of the
DCD file (for both Unix and Windows platforms). Since this is now
failing on Windows with the new compilers in 64-bit mode, I've rewritten
the associated code to use different system calls to determine file
size, and that seems to have cured the problem.

I expect to build a new V4 installer later this morning after I
complete some further tests on other trajectory reader/writer plugins.

Best regards,
  John Stone

On Thu, Dec 17, 2020 at 01:35:18AM +0000, Jason Smith wrote:
> Hi,
> just installed this today (vmd194a50win64-SetupV3) and have been unable to
> open large trajectories :(. BTW I am very very excited to be able to
> address larger amounts of memory on a 64-bit version. Thank You!
> Through some trial and error it seems like the problem lies in the file
> size, not whether the file fits in memory. For e.g.
> 977 MB file in a50 opens, a 2.9 GB does not (28 GB free memory, 32
> installed). For 1.9.3 in the past I always found it would crash when
> trying to use more than around 1.1 - 1.3 GB of memory.
> What's more is that I can't use frame striding to get around it. In 1.9.3
> and 4a48 I can open up my 100 GB files using striding, but I can't open
> the 2.9 GB in a50 using striding.
> I also repeatedly opened a 750 MB DCD in a50 until task manager indicated
> 4.5 GB usage by VMD, so not a 32-bit memory limit. I also tried to open
> the files from HDD vs NVME in case it was a hardware issue.
> The error given is:
> dcdplugin) Could not access file 'E:/temp/6yb7_NPT_Production-2.dcd'.
> ERROR) Could not read file E:/temp/6yb7_NPT_Production-2.dcd
> Cheers,
> -
> Jason Smith
> Post-Doctoral Fellow
> Robert N. Young Lab, Simon Fraser University
> 8888 University Drive, Burnaby, BC, V5A-1S6
> Canada

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