dem — multilevel (GraphMG-style) momentum-conserving contact stabilization. More...

#include <Kokkos_Core.hpp>
#include <utility>
#include <vector>
#include "contact_preprocessing.hpp"
#include "solver_fused.hpp"
#include "solver_velocity.hpp"

Classes
struct	peclet::dem::ContactHierarchy
	Host-side description of one built hierarchy (offsets into the packed group pools). More...

struct	peclet::dem::MlScratch
	Device scratch for the multilevel pass, sized once (see Particles::allocate). More...

struct	peclet::dem::MlCoarseSweep
	The per-manifold coarse-PGS body (translation-only, e = 0, shared fine accumulator) lives in MlCoarseSweep so the per-colour launch loop and the fused whole-cycle kernel share it verbatim. More...

struct	peclet::dem::MlFusedMeta
	Host-POD description of a built hierarchy for the fused coarse-cycle kernel (fixed-size arrays: kernel argument by value). More...

struct	peclet::dem::MlFusedCtx
	Fused-coarse-cycle context: flat per-level colour offsets on device + barrier + meta. More...

Namespaces
namespace	peclet

namespace	peclet::dem

namespace	peclet::dem::mldetail

Functions
float	peclet::dem::mldetail::effMass (float invMass)
	Effective mass with fixed bodies (invMass == 0) mapped to a huge-but-finite mass so the momentum-weighted restriction stays finite and the group's inverse mass underflows to ~0.

bool	peclet::dem::mldetail::eligible (const ManifoldC &m, int idx, Kokkos::View< const int , CpMem > mColor, Kokkos::View< const float , CpMem > vn0, Kokkos::View< const float [3], CpMem > vt0, Kokkos::View< const unsigned char , CpMem > persistent, Kokkos::View< const float *[3], CpMem > posPred, F3 gHat, float qsThr, int gateMask)
	Coarse-eligibility of a manifold: active + base-coloured (non-dup) + quasi-static approach (\|vn0\| <= qsThr: a ballistic pair is never aggregated, so an impactor keeps its fine-level momentum-conserving physics), plus the gates selected in gateMask.

ContactHierarchy	peclet::dem::buildContactHierarchyKokkos (Kokkos::View< const ManifoldC , CpMem > manifolds, int numManifolds, Kokkos::View< const int , CpMem > realIdx, Kokkos::View< const int , CpMem > mColor, Kokkos::View< const float , CpMem > vn0, Kokkos::View< const float [3], CpMem > vt0, Kokkos::View< const unsigned char , CpMem > persistent, Kokkos::View< const float [3], CpMem > posPred, F3 gHat, Kokkos::View< const float , CpMem > invMass, float qsThr, int gateMask, int numReal, MlScratch &S, Kokkos::View< long long , CpMem > winner, Kokkos::View< std::uint64_t , CpMem > colorMask, bool excludeImmovable=false, Kokkos::View< const unsigned char *, CpMem > asleep={})
	Build the aggregation hierarchy + per-level crossing-manifold colorings.

void	peclet::dem::buildCoarseBucketsKokkos (const ContactHierarchy &H, MlScratch &S, int numManifolds, Kokkos::View< int , CpMem > colorScratch, Kokkos::View< int , CpMem > perm, Kokkos::View< int *, CpMem > cursor, std::vector< std::vector< int > > &offs)
	One multilevel stabilization cycle over an already-built hierarchy: fine colored smoothing is the caller's business; this runs the coarse leg (fine -> coarse), updating velPred in place.

MlFusedCtx	peclet::dem::demMakeMlFusedCtx (CpExec &space, const ContactHierarchy &H, const std::vector< std::vector< int > > &bkOffs, int numManifolds, int numReal, int coarseSweeps, Kokkos::View< int , CpMem > offsDev, Kokkos::View< unsigned , CpMem > bar)
	Build the fused-coarse-cycle context from an already-built hierarchy + its dense buckets: flatten the per-level colour offsets into the pooled device view (async upload) and record the grid-sizing work bound.

void	peclet::dem::multilevelCoarseCycleKokkos (Kokkos::View< const ManifoldC , CpMem > manifolds, int numManifolds, Kokkos::View< const int , CpMem > realIdx, Kokkos::View< const float , CpMem > invMass, Kokkos::View< float [3], CpMem > velPred, Kokkos::View< float , CpMem > lambdaAcc, Kokkos::View< float, CpMem > maxApproach, int numReal, const ContactHierarchy &H, MlScratch &S, int coarseSweeps, Kokkos::View< const float , CpMem > restRel={}, const std::vector< std::vector< int > > bkOffs=nullptr, Kokkos::View< const int , CpMem > bkPerm={}, const MlFusedCtx *fused=nullptr)

Variables
constexpr int	peclet::dem::kMlMaxLevels = 10
	6-bit colour slots per level in the packed word; slot value 63 = not crossing / not eligible at that level (skipped by the coarse sweeps).

constexpr int	peclet::dem::kMlSlotSkip = 63

constexpr int	peclet::dem::mldetail::kGatePersistent = 1
	Optional eligibility gates beyond the quasi-static approach test (a SELECTION, not a sink – impulses stay symmetric; gating only decides which contacts join the coarse problem): kGatePersistent – contact must have existed last substep (a fresh contact is an event).

constexpr int	peclet::dem::mldetail::kGateCone = 2

constexpr int	peclet::dem::mldetail::kGateSlip = 4

Detailed Description

dem — multilevel (GraphMG-style) momentum-conserving contact stabilization.

The principled replacement for the one-sided grounded pass: a collapsing column cannot be arrested by plain symmetric PGS (momentum moves ~one layer per sweep) and the one-sided pass arrests it by DELETING momentum (measured cost: it kills a ballistic impactor's rebound). The multilevel pass instead accelerates momentum TRANSPORT: greedy pairwise aggregation over the quasi-static contact graph builds super-bodies (summed mass, momentum-weighted velocity), and the fine manifolds crossing aggregate boundaries are re-solved with the AGGREGATE masses – the coarse analogue of the held lower side is the genuinely huge inertia of the supported chain, so a wall contact drains a whole column's momentum in one coarse impulse while every impulse stays symmetric (exact momentum conservation; the floor/walls are the only sink).

Structure per trigger (residual above the resting threshold after the main sweeps): build: L levels of matching (ballistic pairs |vn0| > qsThr and walls never merge; stop when matching stalls or the group count is small), per-level group masses, and a per-level graph coloring of the crossing manifolds (6 bits/level packed into one word per manifold; the coloring guarantees group-disjointness within a launch). cycle: per iteration, one fine colored-PGS smoothing sweep, then levels fine -> coarse: restrict (V_g = sum m v / sum m – momentum-conserving), a few colored coarse PGS sweeps (translation-only, e = 0, lambda >= 0 on the SHARED fine accumulator so the force-network ledger stays consistent for warm start + the friction cone's Coulomb bound), prolongate (v_i += dV_g: uniform per aggregate = mass-proportional impulse).

The inequality constraint is respected on every level (Kornhuber-style truncation reduces to: only compressed/quasi-static contacts aggregate or restrict; lambda >= 0 projection is the same accumulator projection as the fine sweep). Friction stays fine-level only.

Definition in file solver_multilevel.hpp.

Classes

Namespaces

Functions

Variables

Detailed Description