Inastemp: A Novel Intrinsics-as-Template Library for Portable SIMD-Vectorization

Code 15

Code extract of the particle interactions example taken from Inastemp and introduced in Section 6.3.

(1) // Scalar interaction

(2) const RealType dx = positionsX[idxTarget] − positionsX[idxSource];

(3) const RealType dy = positionsY[idxTarget] − positionsY[idxSource];

(4) const RealType dz = positionsZ[idxTarget] − positionsZ[idxSource];

(5)

(6) const RealType distance = std::sqrt(dxdx + dydy + dzdz);

(7) const RealType inv_distance = 1/distance;

(8)

(9) if(distance < cutDistance)

(10) potentials[idxTarget] += ( inv_distance physicalValues[idxSource] );

(11) potentials[idxSource] += ( inv_distance physicalValues[idxTarget] );

(12)

(13) else

(14) potentials[idxTarget] += ( inv_distance (physicalValues[idxSource]−constantIfCut) );

(15) potentials[idxSource] += ( inv_distance (physicalValues[idxTarget]−constantIfCut) );

(16)

(17)

(18) // Vectorized using advanced branch manager

(19) const VecType dx = targetX − VecType(&positionsX[idxSource]);

(20) const VecType dy = targetY − VecType(&positionsY[idxSource]);

(21) const VecType dz = targetZ − VecType(&positionsZ[idxSource]);

(22)

(23) const VecType distance = VecType(dxdx + dydy + dzdz).sqrt();

(24) const VecType inv_distance = VecOne/distance;

(25)

(26) const typename VecType::MaskType testRes = (distance < VecCutDistance);

(27)

(28) const VecType sourcesPhysicalValue = VecType(&physicalValues[idxSource]);

(29)

(30) targetPotential += inv_distance VecType::If(testRes).Then([&]()

(31) return sourcesPhysicalValue;

(32) ).Else([&]()

(33) return sourcesPhysicalValue−VecConstantIfCut;

(34) );

(35) const VecType resSource = inv_distance VecType::If(testRes).Then([&]()

(36) return targetPhysicalValue;

(37) ).Else([&]()

(38) return targetPhysicalValue−VecConstantIfCut;

(39) );

(40)

(41) const VecType currentSource = VecType(&potentials[idxSource]);

(42) (resSource+currentSource).storeInArray(&potentials[idxSource]);