Hello, I have recently installed Kwant using miniconda onto my own account (no root access). I installed Python and all its dependencies as well with your help. Thank you!! When I run a code on a single processor, it works fine. When I add more CPUs, each calculation takes longer time. Code builds a system with hopping, on-site repulsion and SOC, with leads, then I calculate the scattering matrix of it. I ran a check with no-Kwant function (a simple summation), calculation takes almost same time independent of number of CPUs. I understand Kwant itself is not a parallel program, but given the same task, it should take same time to finish regardless of how many times it has been called. The code I am using builds 2 systems and calculates 2 smatrices. I paste below the times it takes for each set of CPUs. I am guessing this is an issue with sharing the library, but I am not certain. The time increases faster than linear. Any ideas? Thanks Fatih Single CPU ----------------- hello world from process 0 done system 1 0 0.05028367042541504 done smatrix 1 0 0.23258066177368164 done system 2 0 3.244915723800659 done smatrix 2 0 13.960146427154541 Two CPUs --------------- hello world from process 1 done system 1 1 0.04906630516052246 done smatrix 1 1 0.23961257934570312 done system 2 1 3.5525107383728027 done smatrix 2 1 16.66365075111389 hello world from process 0 done system 1 0 0.045102834701538086 done smatrix 1 0 0.20883417129516602 done system 2 0 2.842400550842285 done smatrix 2 0 14.466880559921265 Four CPUs --------------- hello world from process 1 done system 1 1 0.09960174560546875 done smatrix 1 1 0.630927324295044 done system 2 1 3.514568328857422 done smatrix 2 1 119.35529565811157 hello world from process 2 done system 1 2 0.09219717979431152 done smatrix 1 2 0.8386905193328857 done system 2 2 4.74960732460022 done smatrix 2 2 119.06909513473511 hello world from process 3 done system 1 3 0.13100957870483398 done smatrix 1 3 0.860680341720581 done system 2 3 3.4969165325164795 done smatrix 2 3 120.44963669776917 hello world from process 0 done system 1 0 0.1307511329650879 done smatrix 1 0 0.8210744857788086 done system 2 0 4.6470348834991455 done smatrix 2 0 120.91561484336853 8 CPUs -------------- hello world from process 3 done system 1 3 0.08914065361022949 done smatrix 1 3 1.9215054512023926 done system 2 3 12.615397214889526 done smatrix 2 3 264.25777077674866 hello world from process 1 done system 1 1 0.05163288116455078 done smatrix 1 1 1.5547888278961182 done system 2 1 7.847089767456055 done smatrix 2 1 264.47394609451294 hello world from process 4 done system 1 4 0.05323219299316406 done smatrix 1 4 1.8263118267059326 done system 2 4 8.452224254608154 done smatrix 2 4 258.97272992134094 hello world from process 6 done system 1 6 0.0951833724975586 done smatrix 1 6 1.7297015190124512 done system 2 6 9.489607334136963 done smatrix 2 6 258.52338123321533 hello world from process 7 done system 1 7 0.052448272705078125 done smatrix 1 7 1.3691565990447998 done system 2 7 8.31990361213684 done smatrix 2 7 260.8307328224182 hello world from process 2 done system 1 2 0.0588071346282959 done smatrix 1 2 1.5174744129180908 done system 2 2 5.244871377944946 done smatrix 2 2 242.011638879776 hello world from process 5 done system 1 5 0.05212259292602539 done smatrix 1 5 1.5607316493988037 done system 2 5 5.980914831161499 done smatrix 2 5 251.20327258110046 hello world from process 0 done system 1 0 0.05146503448486328 done smatrix 1 0 1.4909172058105469 done system 2 0 5.17970871925354 done smatrix 2 0 246.73624682426453