a The predicted results obtained by the memristor-based parallel RC system, where the black line represents the ideal target and the red line represents the experimental output from the RC system. Test parameters are set to be M = 4, N = 25, Vmax = 2.5 V and Vmin = −0.8 V. b, c 2-D display of the predicted results under different test parameters, where the M and Vmax in b and c are 4, 2.5 V and 25, 2.0 V, respectively. Vmin and the total reservoir size (M × N) remain unchanged at −0.8 V and 100, respectively. d The prediction error varies with the two test parameters M (1–100) and Vmax (2.0–3.0 V), where the color bar represents the NRMSE (values >0.13 are shown in black in the figure). Vmin and M × N remain unchanged. e The NRMSE changes with the reservoir size in different RC systems including the standard ESN (results in ref. 40), memristor-based parallel RC, and software-simulated one. In both experiment and simulation, the mask length remains constant at 4, and the total reservoir size is adjusted by changing the number of parallel reservoirs N.