# Xtrapol8

Calculation of Fourier difference maps, extrapolated structure factor
amplitudes (ESFAs) and occupancy estimation of low-occupancy triggered
states. Built on cctbx; needs licensed Phenix (>=1.19) and CCP4 at runtime.

- Upstream: https://github.com/ElkeDeZitter/Xtrapol8
- License: MIT

## How it is built

Upstream installation is just "clone or download, keep all files in one
directory". The recipe downloads the release tag tarball from GitHub and
untars it into `$PREFIX/bin`. Loading the module sets `XTRAPOL8_DIR`,
puts `$PREFIX/bin` on `PATH` and auto-loads phenix and ccp4.

Note: release tags switched format at 1.2.8 (`v.1.2.8` with a dot);
the default `urls:` matches the new style, so rebuilding <=1.2.5
versions (tagged `v1.x.y`) would need a per-version `urls:` override.

## Building on Ra

```sh
module use unstable && module load modbuild/2.1.3
cd Xtrapol8
modbuild build 1.2.9
module use MX unstable && module load Xtrapol8/1.2.9
```

## Verifying the install

```sh
which Fextr.py                       # -> .../Xtrapol8/<version>/bin
module list                          # phenix + ccp4 pulled in
phenix.python "$XTRAPOL8_DIR/bin/Fextr.py"   # prints the argument list
```

### Installation remarks

March 2026: From v1.2.6 on, seem to work with phenix/1.21 versions. v1.2.8 is compiled with phenix/1.21 version and needs to be tested to see whether it works.

According to Elke de Zitter (as of Spring 2024) Xtrapol8 only runs with the phenix/1.19 version. 
--> check for new releases...


### Runtime tips

The phenix module with be automatically loaded , but in order to open the GUI one has to do: 

phenix.python ${XTRAPOL8_DIR}/bin/X8_gui.py 

Exectuables in the ${XTRAPOL8_DIR}/bin/ folder are obviously directly callable if the module is loaded... (for instance Fextr.py)