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The thermal history of cosmic gas in the Dark Ages remains largely unknown.It is important to quantify the impact of relevant physics on the IGMtemperature between $z=10$ and $z \sim 30$, in order to interpret recent andoncoming observations, including results reported by EDGES. We revisit the gasheating due to structure formation shocks in this era, using a set of fixedgrid cosmological hydrodynamical simulations performed by three differentcodes. In all our simulations, the cosmic gas is predicted to be in multiphasestate since $z>30$. The gas surrounding high density peaks gradually develops arelation more sharp than $T \propto \rho^{2/3}$, approximately $T \propto\rho^{2}$, from $z=30$ to $z=11$, might due to shock heating. Meanwhile, thegas in void region tends to have a large local mach number, and their thermalstate varies significantly from code to code. In the redshift range $11-20$,the mass fraction of gas shock heated above the CMB temperature in oursimulations is larger than previous semi-analytical results by a factor of 2 to8. At $z=15$, the fraction varies from $\sim 19\%$ to $52 \%$ among differentcodes. Between $z=11$ and $z=20$, the gas temperature $<1/T_{\rm{K}}>_M^{-1}$is predicted to be $\sim 10-20$ K by two codes, much higher than the adiabaticcooling model and some previous works. However, in our simulations performed byRAMSES, $<1/T_{\rm{K}}>_M^{-1}$ is predicted to be even below the temperaturerequired to explain result of the EDGES. Given the fact that different codesgive different predictions, currently, it seems a challenge to make solidprediction on the temperature of gas at $z \sim 17$ in simulations.

The temperature of IGM at high redshifts: shock heating and high mach problem