Fix pedantic warnings in LangevinSampler
Fix pedantic warnings in LangevinSampler

chunshen1987/DistributionSampling,chunshen1987/DistributionSampling,chunshen1987/DistributionSampling,chunshen1987/DistributionSampling,chunshen1987/DistributionSampling,chunshen1987/DistributionSampling