|CosmoChord:||PolyChord + CosmoMC for cosmological parameter estimation and evidence calculation|
Description and installation
CosmoChord is a fork of CosmoMC, which adds nested sampling provided by PolyChord.
.. bash:: git clone --recursive https://github.com/williamjameshandley/CosmoChord cd CosmoChord make export OMP_NUM_THREADS=1 ./cosmomc test.ini
To run, you should add
action=5 to your ini file, and include
batch3/polychord.ini. Consider modifying
If you wish to use Planck data, you should follow the CosmoMC planck instructions, and then run
make clean; make after
You can see the key changes by running:
.. bash:: git remote add upstream https://github.com/cmbant/CosmoMC git fetch upstream git diff --stat upstream/master git diff upstream/master source
The changes to CosmoMC are minor:
- Nested sampling heavily samples the tails of the posterior. This means that there need to be more corrections for these regions that are typically unexplored by the default metropolis hastings tool. This is now implemented by separate CAMB git submodule
- You should not use openmp parallelisation, as this in inefficient when using PolyChord. Instead, you should use pure MPI parallelisation, and you may use as many cores as you have live points.