Add flexibility to VDC

[am1808]

Hi Richard, I was thinking to tweak VDC to allow the possibility for the user to specify which snapshots to process. Is it OK?

[richard-evans]

Hi Andrea, yes indeed - but please base off the VDC branch. There are a few changes in there that will be moved into develop shortly (but default colour space is currently broken and waiting for Daniel to fix it). maybe add a --snapshot command line option, taking individual numbers or ranges, comma separated?

[am1808]

OK. I have created the branch "vdc_based_on_vdc_upstream" which I have just pushed. Could you have a look at it? If it is fine I will do a pull request.

I have created two distinct command line arguments "--frame-start" and "--frame-final" to allow an independent control of the initial and final snapshots to render.

[daniel-meilak]

I've noticed an issue with how vdc processes the spin metadata files. Without the --frame-final parameter provided manually, the program doesn't know the actual number of files and always gives the error "Error! Spins metadata file spins-000000xx.meta cannot be opened. Exiting".

This happens because the vdc_final_file_id is set to a large number by default and never gets changed.

I'm not sure how to fix this since none of the input files say how many meta data files there are.

[daniel-meilak]

I think I found out how to fix it. Looks like I had made a small change to spins.cpp with the aim of helping that actually caused this issue

[daniel-meilak]

So, I added an Error massage that triggered if you provided a "--frame-final" which was larger than the number of frames availible. Unfortunately, this would always trigger if frame-final wasn't provided since the default value is 99999.

It would be nice if we could set the default value of frame-final internally but I'm guessing this is difficult to implement since the number of spin meta files changes according to the number of processors used int the simulation?

[richard-evans]

Yep, the problem is that the spin file parsing exits when it can't find the next file - it should actually fail silently at this step (an error should only be triggered if a data file cannot be found). The following patch fixes the bug.

diff --git a/util/vdc/spins.cpp b/util/vdc/spins.cpp
index 43d6836..de84a67 100644
--- a/util/vdc/spins.cpp
+++ b/util/vdc/spins.cpp
@@ -114,9 +114,10 @@ bool read_spin_metadata(unsigned int file_id){

// check for open file, if not open then end program, end of snapshots
if(!smfile.is_open()){

•  std::cerr << "Error! Spins metadata file spins-" << std::setfill('0') << std::setw(8)
  

•  << file_id << ".meta cannot be opened. Exiting" << std::endl;
  

•  exit(1);
  

•  //std::cerr << "Error! Spins metadata file spins-" << std::setfill('0') << std::setw(8)
  

•  //<< file_id << ".meta cannot be opened. Exiting" << std::endl;
  

•  //exit(1);
  

•  return false;
  

  }