`im_sv_dumps` produces empty (0-byte) files in tissue simulations

Question

In a tissue opencarp run, imp_region[0].im_sv_dumps creates one file per state variable but every file stays 0 bytes, even though the run completes and 'vm.igb' is written correctly. No warning printed.

## parameters.par ##

num_imp_regions                         = 1

imp_region[0].im                           = tenTusscherPanfilov

imp_region[0].num_IDs                = 1

imp_region[0].ID[0]                      = 1

imp_region[0].im_sv_dumps       = "Cai,D,F,F2,H"

gregion[0].num_IDs                      = 1

gregion[0].ID[0]                        = 1

gregion[0].g_il                         = 0.056

gregion[0].g_it                         = 0.056

gregion[0].g_in                         = 0.056

gregion[0].g_el                         = 0.056

gregion[0].g_et                         = 0.056

gregion[0].g_en                         = 0.056

num_stim                                = 1

stimulus[0].stimtype                    = 0

stimulus[0].strength                    = 100

stimulus[0].duration                    = 2

stimulus[0].npls                        = 1

meshname                                = mesh1/block

simID                                   = 2026-09-07_TT06

tend                                    = 500.0

dt                                      = 100.0

spacedt                                 = 1.0

timedt                                  = 5.0

bidomain                                = 0

Answer 1

Thanks for the clear report. I reproduced it, and it's a bug in openCARP, not a problem with your setup.

In tissue simulations, im_sv_dumps opens one output file per state variable, but the routine that writes to them is only called by the single-cell tool bench. openCARP never calls it, so the files stay empty. The files were created, which means your variable names are valid. I've opened an issue to fix it: https://git.opencarp.org/openCARP/openCARP/-/work_items/539

Until then, please use gvec output instead. It writes one .igb file per state variable every spacedt, like vm.igb:

num_gvecs      = 5

gvec[0].name   = Cai

gvec[0].ID[0]  = Cai

gvec[1].name   = D

gvec[1].ID[0]  = D

gvec[2].name   = F

gvec[2].ID[0]  = F

gvec[3].name   = F2

gvec[3].ID[0]  = F2

gvec[4].name   = H

gvec[4].ID[0]  = H

gvec[i].ID[j] is the variable name in imp region j, so with more imp regions you set one ID per region. You can read the resulting files with igbextract, or in meshalyzer/ParaView like vm.igb.