p.Chaos.XPBDBending.ISPC.ParallelBatchSize
p.Chaos.XPBDBending.ISPC.ParallelBatchSize
#Overview
name: p.Chaos.XPBDBending.ISPC.ParallelBatchSize
This variable is created as a Console Variable (cvar).
- type:
Var - help:
Parallel batch size for ISPC XPBDBending constraints
It is referenced in 5 C++ source files.
#Summary
#Usage in the C++ source code
The purpose of p.Chaos.XPBDBending.ISPC.ParallelBatchSize is to control the parallel batch size for ISPC (Intel SPMD Program Compiler) XPBDBending constraints in Unreal Engine’s Chaos physics system. This setting variable is specifically used in the anisotropic bending constraints implementation for soft body simulation.
This setting variable is primarily used in the Chaos module, which is part of Unreal Engine’s experimental physics system. It’s specifically utilized in the XPBDAnisotropicBendingConstraints implementation.
The value of this variable is set using an FAutoConsoleVariableRef, which allows it to be modified at runtime through console commands. It’s initialized with a default value of 1028.
The associated variable Chaos_XPBDBending_ISPC_ParallelBatchSize directly interacts with p.Chaos.XPBDBending.ISPC.ParallelBatchSize. They share the same value, with Chaos_XPBDBending_ISPC_ParallelBatchSize being the actual variable used in the code.
Developers must be aware that this variable affects the parallelization of XPBD anisotropic bending constraint calculations. It determines the size of batches processed in parallel, which can impact performance and potentially simulation accuracy.
Best practices when using this variable include:
- Adjusting it based on the specific hardware and scene complexity to optimize performance.
- Testing different values to find the optimal balance between parallelization overhead and computation efficiency.
- Considering the relationship with Chaos_XPBDBending_ISPC_MinNumParallelBatches when tuning performance.
Regarding the associated variable Chaos_XPBDBending_ISPC_ParallelBatchSize:
- Its purpose is the same as p.Chaos.XPBDBending.ISPC.ParallelBatchSize, serving as the actual variable used in the code.
- It’s used in the Chaos physics system, specifically in the XPBDAnisotropicBendingConstraints implementation.
- Its value is set by the console variable p.Chaos.XPBDBending.ISPC.ParallelBatchSize.
- It directly interacts with calculations determining batch sizes for parallel processing of bending constraints.
- Developers should be aware that modifying the console variable will affect this associated variable’s value.
- Best practices include monitoring its impact on performance and adjusting it in conjunction with other related variables for optimal results.
#References in C++ code
#Callsites
This variable is referenced in the following C++ source code:
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/Chaos/XPBDAnisotropicBendingConstraints.cpp:26
Scope (from outer to inner):
file
namespace Chaos::Softs
Source code excerpt:
static int32 Chaos_XPBDBending_ISPC_ParallelBatchSize = 1028;
static int32 Chaos_XPBDBending_ISPC_MinNumParallelBatches = 1028; // effectively disabled for now
FAutoConsoleVariableRef CVarChaosXPBDBendingISPCParallelBatchSize(TEXT("p.Chaos.XPBDBending.ISPC.ParallelBatchSize"), Chaos_XPBDBending_ISPC_ParallelBatchSize, TEXT("Parallel batch size for ISPC XPBDBending constraints"));
FAutoConsoleVariableRef CVarChaosXPBDBendingISPCMinNumParallelBatches(TEXT("p.Chaos.XPBDBending.ISPC.MinNumParallelBatches"), Chaos_XPBDBending_ISPC_MinNumParallelBatches, TEXT("Min number of batches to invoke parallelFor ISPC XPBDBending constraints"));
FXPBDAnisotropicBendingConstraints::FXPBDAnisotropicBendingConstraints(const FSolverParticlesRange& InParticles,
const FTriangleMesh& TriangleMesh,
const TArray<TVec3<FVec2f>>& FaceVertexPatternPositions,
const TMap<FString, TConstArrayView<FRealSingle>>& WeightMaps,
#Associated Variable and Callsites
This variable is associated with another variable named Chaos_XPBDBending_ISPC_ParallelBatchSize. They share the same value. See the following C++ source code.
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/Chaos/XPBDAnisotropicBendingConstraints.cpp:24
Scope (from outer to inner):
file
namespace Chaos::Softs
Source code excerpt:
extern int32 Chaos_XPBDBending_ParallelConstraintCount;
static int32 Chaos_XPBDBending_ISPC_ParallelBatchSize = 1028;
static int32 Chaos_XPBDBending_ISPC_MinNumParallelBatches = 1028; // effectively disabled for now
FAutoConsoleVariableRef CVarChaosXPBDBendingISPCParallelBatchSize(TEXT("p.Chaos.XPBDBending.ISPC.ParallelBatchSize"), Chaos_XPBDBending_ISPC_ParallelBatchSize, TEXT("Parallel batch size for ISPC XPBDBending constraints"));
FAutoConsoleVariableRef CVarChaosXPBDBendingISPCMinNumParallelBatches(TEXT("p.Chaos.XPBDBending.ISPC.MinNumParallelBatches"), Chaos_XPBDBending_ISPC_MinNumParallelBatches, TEXT("Min number of batches to invoke parallelFor ISPC XPBDBending constraints"));
FXPBDAnisotropicBendingConstraints::FXPBDAnisotropicBendingConstraints(const FSolverParticlesRange& InParticles,
const FTriangleMesh& TriangleMesh,
const TArray<TVec3<FVec2f>>& FaceVertexPatternPositions,
const TMap<FString, TConstArrayView<FRealSingle>>& WeightMaps,
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/Chaos/XPBDAnisotropicBendingConstraints.cpp:692
Scope (from outer to inner):
file
function void FXPBDAnisotropicBendingConstraints::Apply
Source code excerpt:
const int32 ColorStart = ConstraintsPerColorStartIndex[ConstraintColorIndex];
const int32 ColorSize = ConstraintsPerColorStartIndex[ConstraintColorIndex + 1] - ColorStart;
if (ColorSize >= Chaos_XPBDBending_ISPC_ParallelBatchSize * Chaos_XPBDBending_ISPC_MinNumParallelBatches)
{
const int32 NumBatches = FMath::DivideAndRoundUp(ColorSize, Chaos_XPBDBending_ISPC_ParallelBatchSize);
PhysicsParallelFor(NumBatches, [this, &Particles, ColorStart, ColorSize,
ParallelBatchSize = Chaos_XPBDBending_ISPC_ParallelBatchSize,
Dt, &ExpStiffnessValue, &ExpBucklingValue, DampingRatioValue](const int32 BatchIndex)
{
const int32 BatchStart = BatchIndex * ParallelBatchSize;
const int32 BatchEnd = FMath::Min((BatchIndex + 1) * ParallelBatchSize, ColorSize);
ispc::ApplyXPBDAnisotropicBendingDampingConstraints(
(ispc::FVector4f*)Particles.GetPAndInvM().GetData(),
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/Chaos/XPBDAnisotropicBendingConstraints.cpp:752
Scope (from outer to inner):
file
function void FXPBDAnisotropicBendingConstraints::Apply
Source code excerpt:
const int32 ColorStart = ConstraintsPerColorStartIndex[ConstraintColorIndex];
const int32 ColorSize = ConstraintsPerColorStartIndex[ConstraintColorIndex + 1] - ColorStart;
if (ColorSize >= Chaos_XPBDBending_ISPC_ParallelBatchSize * Chaos_XPBDBending_ISPC_MinNumParallelBatches)
{
const int32 NumBatches = FMath::DivideAndRoundUp(ColorSize, Chaos_XPBDBending_ISPC_ParallelBatchSize);
PhysicsParallelFor(NumBatches, [this, &Particles, ColorStart, ColorSize,
ParallelBatchSize = Chaos_XPBDBending_ISPC_ParallelBatchSize,
Dt, &ExpStiffnessValue, &ExpBucklingValue, DampingRatioValue](const int32 BatchIndex)
{
const int32 BatchStart = BatchIndex * ParallelBatchSize;
const int32 BatchEnd = FMath::Min((BatchIndex + 1) * ParallelBatchSize, ColorSize);
ispc::ApplyXPBDAnisotropicBendingConstraintsWithDamping(
(ispc::FVector4f*)Particles.GetPAndInvM().GetData(),
#Loc: <Workspace>/Engine/Source/Runtime/Experimental/Chaos/Private/Chaos/XPBDAnisotropicBendingConstraints.cpp:812
Scope (from outer to inner):
file
function void FXPBDAnisotropicBendingConstraints::InitColor
function void FXPBDAnisotropicBendingConstraints::Apply
Source code excerpt:
const int32 ColorStart = ConstraintsPerColorStartIndex[ConstraintColorIndex];
const int32 ColorSize = ConstraintsPerColorStartIndex[ConstraintColorIndex + 1] - ColorStart;
if (ColorSize >= Chaos_XPBDBending_ISPC_ParallelBatchSize * Chaos_XPBDBending_ISPC_MinNumParallelBatches)
{
const int32 NumBatches = FMath::DivideAndRoundUp(ColorSize, Chaos_XPBDBending_ISPC_ParallelBatchSize);
PhysicsParallelFor(NumBatches, [this, &Particles, ColorStart, ColorSize,
ParallelBatchSize = Chaos_XPBDBending_ISPC_ParallelBatchSize,
Dt, &ExpStiffnessValue, &ExpBucklingValue](const int32 BatchIndex)
{
const int32 BatchStart = BatchIndex * ParallelBatchSize;
const int32 BatchEnd = FMath::Min((BatchIndex + 1) * ParallelBatchSize, ColorSize);
ispc::ApplyXPBDAnisotropicBendingConstraints(
(ispc::FVector4f*)Particles.GetPAndInvM().GetData(),