Julien's most updated code has all valence derivatives with the sign changed, so md_val needs to flip the sign. Also, the reader does not write "_d1, _d2" in the derivatives anymore for the new data files, so md_val does not look for "_d1, _d2". You need to select by hand which correlators are your valence derivatives, looking at the log file e.g.

This reverts commit f3531bef.

several functions, needs testing

functions for TSM runs.
read_mesons_correction -> read correction runs (exact + sloppy solutions)
corr_obs_TSM -> create Corr with <O_sloppy> + <O_correction>

Study and preliminary tests  on correlated fits