Request: increase maximum allowed pressure

[gmboyer]

The maximum pressure hard-coded into EQ3/6 is 10 kb. I assume this is because the program originally assumed users were using SUPCRT and IAPWS water models that are applicable up to 5 kb and 10 kb, respectively. Unfortunately, this hard-coded cap does not allow users to take advantage of the Deep Earth Water (DEW) model that takes calculations up to 60 kb. By increasing the pressure cap, speciation calculations can successfully be performed in an EQ3/6 backend using the DEW water model (for example, pyDEW and aqequil).

The pressure cap can be increased to 90 kb with edits to the following two files:

git clone https://github.com/39alpha/eq3_6.git
cd eq3_6
sed -i 's/data presmx \/10000.\//data presmx \/90000.\//' src/eq3nr/src/eq3nr.f
sed -i 's/data presmx \/10000.\//data presmx \/90000.\//' src/eq6/src/gpress.f
make
sudo make install

I request that the pressure maximum be increased to 90 kb (or at least 60 kb) to provide support for DEW speciation calculations.

[dglmoore]

@gmboyer I can take a stab at this. My only concern would be validating the change. Up to this point, we've treated the original {d,3,6}* files from the v8 release as "ground truth" for testing purposes. Do you have any suggestions for how I might sensibly test the output for a system outside that range?

One possibility would be to produce d0, 3i and 6i inputs, generate the outputs and manually validate them. They then serve as the ground truth above 10kb going forward.

Thoughts?

[gmboyer]

@dglmoore I typically assume the work of Dimitri Sverjensky and Simon Matthews to represent the "ground truth" when it comes to the DEW model. Dimitri wrote the original DEW paper and Simon works closely with him on the technical side.

Do you have any suggestions for how I might sensibly test the output for a system outside that range?

The "Resources" page of the DEW community website has a section called EQ CODES with a bunch of zip files containing EQ3/6 data0 files and example input and output files for a variety of temperatures and pressures up to 1000 degrees C and 50 kb. The downside is that (I think) these files were all created using EQ3/6 version 7 and aren't compatible with version 8. This makes it difficult to reproduce these DEW examples.

Another avenue is to attempt to reproduce the example in this pyDEW tutorial created by Simon Matthews. Here's the mybinder link. It allows you to create data0 files, input, and output files using (I think) EQ3/6 v8 at whatever temperature and pressure you want. I'll email you some files I created at 500 K and 8.5 kb and 50 kb. You might be able to run these directly with runeqpt and then runeq3 using v8 after increasing the pressure cap.

[dglmoore]

Thanks for the information, @gmboyer.

I am working on improving the quality of our test suite at the moment. That's a slightly higher priority for me as a.) the test suite we have is hacky and broken (cross-platform tests for floating-point computations are tricky, as I'm sure you know) and b.) I'd like to at least have some false confidence that I'm not breaking anything when I make changes.

Once that is done, I will knock this issue out.

[gmboyer]

@dglmoore Sounds good!

[dglmoore]

@gmboyer There's a draft PR for this change: #16.

Existing tests all pass, but it's going to take a bit for me to get specialized tests for the feature setup. The files you provided seem to be in an older format, so I'm going to have to convert them.

In the meantime, feel free to take the changes for a spin.

[gmboyer]

@dglmoore Excellent! Thank you.