Hm, I think I figured out the problem…
When having multicomponent system, the adsorption driving force or the source term is Free sites = (effective capacity) − (already bound protein). The effective capacity changes depending on the ACT parameters. Under certain parameter set, effective capacity drops too quickly and the free sites become slightly negative. At first I thought this is fine because this is just desorption, but desorption is actually controlled by the sink term (k_d*q). So a negative source term becomes unphysical. Whenever this happens, IDAS line search starts to linger.
Considering physically the source term can’t be negative, my current fix is to implement a softplus function that regularizes the value of free sites, so it does not drop below zero. After this fix your simulation started to work and the simulation time becomes normal. Results are below:
It might take a while to test, document and release this patch. If you need a version that works urgently, please let me know and I can send you a pre-compiled version of cadet-cli.exe via DM.