Cannot run hi_class with alpha_b ~ -0.56, alpha_m ~ 1.32

[matteograsso98]

Hi,

I am trying to calculate the growth factor for Horndeski gravity, for alpha_b and alpha_m equal to parameters_smg__2 ~ -0.56, parameters_smg__3 ~ 1.32 (propto_omega parameterisation). However, I don't understand why I run into an error message as those values come from my best-fit chain (Montepython + hi_class for CMB x KiDS x BOSS). I don't think I should have problem with stability checks because, as I said, I got those values from my best-fit chain.

The error message reads:

Traceback (most recent call last):
  File "prova.py", line 35, in <module>
    cosmo.compute()
  File "classy.pyx", line 344, in classy.Class.compute
classy.CosmoComputationError: 

Error in Class: perturb_init(L:362) :error in perturb_solve(ppr, pba, pth, ppt, index_md, index_ic, index_k, pppw[thread]);
=>perturb_solve(L:2397) :error in generic_evolver(perturb_derivs, interval_limit[index_interval], interval_limit[index_interval+1], ppw->pv->y, ppw->pv->used_in_sources, ppw->pv->pt_size, &ppaw, ppr->tol_perturb_integration, ppr->smallest_allowed_variation, perturb_timescale, ppr->perturb_integration_stepsize, ppt->tau_sampling, tau_actual_size, perturb_sources, perhaps_print_variables, ppt->error_message);
=>evolver_ndf15(L:379) :error in (*derivs)(tnew,ynew+1,f0+1,parameters_and_workspace_for_derivs,error_message);
=>perturb_derivs(L:6870) :error in perturb_einstein(ppr, pba, pth, ppt, index_md, k, tau, y, ppw);
=>perturb_einstein(L:5201) :condition (isnan(ppw->pvecmetric[ppw->index_mt_vx_prime_prime_smg])) is true;  Isnan v_X'' at a =7.475100e-09 !