Mobility: first idea for fast pow implementation (3ee9e10e) · Commits · XRFLab109 / Allpix Squared

src/physics/Mobility.hpp

+40 −1

Original line number	Diff line number	Diff line
		@@ -87,7 +87,6 @@ namespace allpix {
		double hole_Vm_;
		double hole_Beta_;

		private:
		double electron_Ec_;
		double hole_Ec_;
		};
		@@ -106,6 +105,44 @@ namespace allpix {
		}
		};

		/**
		* @ingroup Models
		* @brief Canali mobility model
		*
		* This model differs from the Jacoboni version only by the value of the electron v_m. The difference is most likely a
		* typo in the Jacoboni reproduction of the parametrization, so this one can be considered the "original".
		*/
		class CanaliFast : virtual public Canali {
		public:
		explicit CanaliFast(SensorMaterial material, double temperature)
		: JacoboniCanali(material, temperature), Canali(material, temperature) {
		LOG(WARNING) << "This mobility model uses an approximative pow implementation and might be less accurate.";
		}

		double operator()(const CarrierType& type, double efield_mag, double) const override {
		// Compute carrier mobility from constants and electric field magnitude
		if(type == CarrierType::ELECTRON) {
		return electron_Vm_ / electron_Ec_ /
		fastPow(1. + fastPow(efield_mag / electron_Ec_, electron_Beta_), 1.0 / electron_Beta_);
		} else {
		return hole_Vm_ / hole_Ec_ / fastPow(1. + fastPow(efield_mag / hole_Ec_, hole_Beta_), 1.0 / hole_Beta_);
		}
		};

		private:
		// Fast approximative pow implementation from
		// https://martin.ankerl.com/2012/01/25/optimized-approximative-pow-in-c-and-cpp/
		inline double fastPow(double a, double b) const {
		union {
		double d;
		int x[2];
		} u = {a};
		u.x[1] = static_cast<int>(b * (u.x[1] - 1072632447) + 1072632447);
		u.x[0] = 0;
		return u.d;
		};
		};

		/**
		* @ingroup Models
		* @brief Hamburg (Klanner-Scharf) parametrization for <100> silicon
		@@ -557,6 +594,8 @@ namespace allpix {
		model_ = std::make_unique<JacoboniCanali>(material, temperature);
		} else if(model == "canali") {
		model_ = std::make_unique<Canali>(material, temperature);
		} else if(model == "canali_fast") {
		model_ = std::make_unique<CanaliFast>(material, temperature);
		} else if(model == "hamburg") {
		model_ = std::make_unique<Hamburg>(material, temperature);
		} else if(model == "hamburg_highfield") {