---
name: DIALS core meeting 2021-01-28
tags: core meeting
---

# DIALS core meeting 2021-01-28

[](https://hackmd.io/AvPg_nqbRA2Mkwi_8qdFew)

## Previous Actions

* [ ] MG+ND: write a proposal for ['overall architecture discussion'](https://dials.github.io/kb/core/20200903) and ['new installer'](https://dials.github.io/kb/core/20200903)
* [ ] MG+ND: Come up with a proposal to [move away from all code being in header files](https://dials.github.io/kb/core/20201001) and consolidate into a single library
* [x] ND: update `CONTRIBUTING` to include a soft-imposition of [stable master](https://dials.github.io/kb/core/20200903#stable-master-branch), [dials#1353](https://github.com/dials/dials/issues/1353).
* [x] MG to look into and see if we can make a reasonable change otherwise we can drop it
* [ ] MG: organise a [typing intro lecture](https://dials.github.io/kb/core/20200917#typing-mypy), likely to happen in Q2.
* [ ] [cbflib conda-forge package](https://dials.github.io/kb/core/20201125#cbflib-conda-forge-package)
* [ ] ND to prepare an agenda for the HDRMX meeting in March
* [ ] ASB to organise a side-meeting next to the HDRMX workshop
* [ ] ASB to explore what should happen to cbflib maintenance in the future
* [ ] ND to set up a [`cbflib_adaptbx` pull request](https://dials.github.io/kb/core/20201125#cbflib_adaptbx-dependency) for MAR detector fixes. Verify with `labelit_regression`.
* [x] GW: write [dxtbx rewrite project proposal](https://dials.github.io/kb/core/20201209#discussion).
* [x] DLS: review [Multiple stills view (#1463)](https://github.com/dials/dials/pull/1463) by next meeting. If not happened, [merge straight in pending news](https://dials.github.io/kb/core/20210114#dials).
* [x] MG/ND/ASB: merge [`is_stills` PR (#1508)](https://github.com/dials/dials/pull/1508) with MG to refactor test, ND to add newsfragment, [ASB to merge. Proviso to please add a ticket](https://dials.github.io/kb/core/20210114#dials) that we will review this as part of the dx2 work.

## Agenda

### Per-image analysis-related PRs

Bug fix (critical):
PR [dxtbx#289](https://github.com/cctbx/dxtbx/pull/289) Ensure format instance is cached when first read
- Format classes constructed directly by the PIA service do not take advantage of the format cache, causing construction twice. On subsequent images, still always constructed the format class to identify (and then used cache for actual spotfinding)
- Also fixes [dxtbx#245](https://github.com/cctbx/dxtbx/pull/245) (format_instance caching leads to wrong data when reading the same file twice)
- ASB: will review today

Performance:
PR [dxtbx#279](https://github.com/cctbx/dxtbx/pull/279) NeXus: avoid unnecessarily walking the full tree

Housekeeping - not so critical:
* PR [dxtbx#286](https://github.com/cctbx/dxtbx/pull/286) DataFactory: if VDS don't also include individual external datasets
* PR [dxtbx#288](https://github.com/cctbx/dxtbx/pull/288) Construct Experiments directly rather than via DataBlocks
* ASB to run xfel-regression tests [as per comment](https://github.com/cctbx/dxtbx/pull/288#issuecomment-769206024)

### Soft-stable master ([dials#1560](https://github.com/dials/dials/issues/1560))
The process we agreed in [dials#1353](https://github.com/dials/dials/issues/1353) was to go soft-stable master for a month, then reevaluate whether to make it a requirement.

PR [dials#1560](https://github.com/dials/dials/issues/1560) changes the contribution guidelines to that effect.

PR [dxtbx#287](https://github.com/cctbx/dxtbx/pull/287) is a half-move towards stable master in dxtbx.

Outcome: Both can go in.

### Drop Python 2 idioms and compatibility fixes ([dials#1567](https://github.com/dials/dials/pull/1567))

There is no further benefit to keeping old constructs around, so this pull request cleans out a couple 1000 lines of old code.

Outcome:
* ASB to add xfel test instructions to the PR (xfel-regression, ucmetrics, simtbx, etc.), for GW to test.
* If tests pass according to instructions PR can be merged.

### dx2 proposal

* Move proposal into a `.md` in the dx2 repository?
* MG's migration proposal:
* Install `dx2` next to, and in addition to `dxtbx`.
* Eventually dxtbx and dx2 need to be able to co-exist anyway.
* Remove C++ code from `dx2` for now, as that fixes conflicts with flex types. Then we can get started with `dx2` right away.
* `dx2` can import the C++ bits from `dxtbx` in the first instance
* Allows us to figure out how to build C++ in `dx2` with `dx2` being a normal python package.
* Tricky bit comes in once we need to diverge in C++ land. I guess it might help that we want to base data structures primarily off numpy rather than flex?

Conversation on this is still ongoing on the mailing list
* Overall the plan is to leave dxtbx in place so that existing software doesnt have to be changed.
* There is no plan to drop format class support.
* ASB to reply on list
* GW to merge all the different discussion strains together

### dials.index: create new experiments
*not discussed in this meeting*

dials.index should (or should not) create new experiments with crystals in rather than modifying in place existing experiments [as proposed in this issue](https://github.com/dials/dials/issues/1029)

### Next meeting

Thursday, February 11th, 4pm UK time, 8am PDT.