add instructions in readme that you may have to install gsl libraries if building locally

[sbillinge]

...and give commands for macos and ubuntu. See Slack for info.

[bobleesj]

On MacOS (Worked for @bobleesj M1)

brew install gsl

On ubuntu (worked for @sbillinge )

sudo apt-get update
sudo apt-get install libgsl-dev

The error message before was:

clang++ -DNDEBUG -fwrapv -O2 -Wall -fPIC -O2 -isystem /Users/imac/miniconda3/envs/pdffit2_test/include -arch arm64 -fPIC -O2 -isystem /Users/imac/miniconda3/envs/pdffit2_test/include -arch arm64 -I/private/var/folders/yd/2758vf317zggm0n0mfmk0tpw0000gn/T/pip-install-dr9tinaa/diffpy-pdffit2_9a1c50a0b0e64854a8cff6bf93d0732f -I/Users/imac/miniconda3/envs/pdffit2_test/include/python3.11 -c src/extensions/libpdffit2/pdf.cc -o build/temp.macosx-11.0-arm64-cpython-311/src/extensions/libpdffit2/pdf.o -std=c++11 -Wall -Wno-write-strings -O3 -funroll-loops -ffast-math
      src/extensions/libpdffit2/pdf.cc:29:10: fatal error: 'gsl/gsl_errno.h' file not found
      #include <gsl/gsl_errno.h>
               ^~~~~~~~~~~~~~~~~
      1 error generated.
      error: command '/usr/bin/clang++' failed with exit code 1

[Tieqiong]

@sbillinge I'm not entirely sure but isn't gsl and g++ only required if we pip install? If people install from Conda (which we want them to do) then this doesn't seem necessary.

[sbillinge]

yes, that's right. It is maybe good enough to leave it here in the issues and then repost to diffpy-users if anyone asks about it?

[Tieqiong]

Just for reference, an easier way might be instead of installing gsl globally we can install it inside of the Conda environment by running conda install gsl. gsl is also one of the requirement for building for diffpy.pdffit2.

[sbillinge]

Just for reference, an easier way might be instead of installing gsl globally we can install it inside of the Conda environment by running conda install gsl. gsl is also one of the requirement for building for diffpy.pdffit2.

yes, even better if it works.