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Hello all, I'm having some trouble running fnirt with the "--inwarp" option. In trying to figure out where the error was coming from, I've been trying a simple command: $ fnirt --in=dti_b0-bet --inwarp=b0_nl_MNI.reg --ref=MNI152_T2_2mm_brain.nii.gz --iout=b0_nlagain_MNI --cout=b0_nlagain_MNI.reg Error occured during estimation at first level of subsampling Exception thrown with message: SpMat::DiagPrecond: Cannot condition singular matrix This same command executes without trouble if I take out the "inwarp" option. I saw elsewhere that fnirt doesn't like volumes with "nan" values, but none of the volumes I'm using have any. Also, the command executes when run with an affine initialization instead of the inwarp. Any insight you could offer would be greatly appreciated! -benjamin