/*
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/** @file Implementation of the post processing to improve the
* cache locality of a mesh.
*
* The algorithm is roughly basing on this paper:
* http://www.cs.princeton.edu/gfx/pubs/Sander_2007_%3ETR/tipsy.pdf
*/
// STL headers
#include
#include
#include
// public ASSIMP headers
#include "../include/DefaultLogger.h"
#include "../include/aiPostProcess.h"
#include "../include/aiMesh.h"
#include "../include/aiScene.h"
// internal headers
#include "ImproveCacheLocality.h"
#include "VertexTriangleAdjacency.h"
using namespace Assimp;
#if _MSC_VER >= 1400
# define sprintf sprintf_s
#endif
// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
ImproveCacheLocalityProcess::ImproveCacheLocalityProcess()
{
// nothing to do here
configCacheDepth = 12; // hardcoded to 12 at the moment
}
// ------------------------------------------------------------------------------------------------
// Destructor, private as well
ImproveCacheLocalityProcess::~ImproveCacheLocalityProcess()
{
// nothing to do here
}
// ------------------------------------------------------------------------------------------------
// Returns whether the processing step is present in the given flag field.
bool ImproveCacheLocalityProcess::IsActive( unsigned int pFlags) const
{
return (pFlags & aiProcess_ImproveCacheLocality) != 0;
}
// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void ImproveCacheLocalityProcess::Execute( aiScene* pScene)
{
DefaultLogger::get()->debug("ImproveCacheLocalityProcess begin");
for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
{
this->ProcessMesh( pScene->mMeshes[a],a);
}
DefaultLogger::get()->debug("ImproveCacheLocalityProcess finished. ");
}
// ------------------------------------------------------------------------------------------------
// Improves the cache coherency of a specific mesh
void ImproveCacheLocalityProcess::ProcessMesh( aiMesh* pMesh, unsigned int meshNum)
{
ai_assert(NULL != pMesh);
// check whether the input data is valid ->
// - there must be vertices and faces (haha)
// - all faces must be triangulated
if (!pMesh->HasFaces() || !pMesh->HasPositions())return;
// find the input ACMR ...
unsigned int* piFIFOStack = new unsigned int[this->configCacheDepth];
::memset(piFIFOStack,0xff,this->configCacheDepth*sizeof(unsigned int));
unsigned int* piCur = piFIFOStack;
const unsigned int* const piCurEnd = piFIFOStack + this->configCacheDepth;
// count the number of cache misses
unsigned int iCacheMisses = 0;
const aiFace* const pcEnd = pMesh->mFaces+pMesh->mNumFaces;
for (const aiFace* pcFace = pMesh->mFaces;pcFace != pcEnd;++pcFace)
{
if (3 != pcFace->mNumIndices)
{
DefaultLogger::get()->error("Unable to improve cache locality of non-triangulated faces");
delete[] piFIFOStack;
return;
}
// although it has not been tested, I'm quite sure degenerated triangles
// would crash if the algorithm was applied to them
#if (defined _DEBUG)
if (pcFace->mIndices[0] == pcFace->mIndices[1] ||
pcFace->mIndices[2] == pcFace->mIndices[1] ||
pcFace->mIndices[2] == pcFace->mIndices[0])
{
DefaultLogger::get()->error("ImproveCacheLocalityProcess: There may be no degenerated triangles ");
return;
}
#endif
for (unsigned int qq = 0; qq < 3;++qq)
{
bool bInCache = false;
for (unsigned int* pp = piFIFOStack;pp < piCurEnd;++pp)
{
if (*pp == pcFace->mIndices[qq])
{
// the vertex is in cache
bInCache = true;
break;
}
}
if (!bInCache)
{
++iCacheMisses;
if (piCurEnd == piCur)piCur = piFIFOStack;
*piCur++ = pcFace->mIndices[qq];
}
}
}
delete[] piFIFOStack;
float fACMR = (float)iCacheMisses / pMesh->mNumFaces;
if (3.0 == fACMR)
{
char szBuff[128]; // should be sufficiently large in every case
// the JoinIdenticalVertices process has not been executed on this
// mesh, otherwise this value would normally be at least minimally#
// smaller than 3.0 ...
::sprintf(szBuff,"Mesh %i: JIV-Step has not been executed properly (precondition)",meshNum);
DefaultLogger::get()->warn(szBuff);
return;
}
// first we need to build a vertex-triangle adjacency list
VertexTriangleAdjacency adj(pMesh->mFaces,pMesh->mNumFaces, pMesh->mNumVertices,true);
// build a list to store per-vertex caching time stamps
unsigned int* const piCachingStamps = new unsigned int[pMesh->mNumVertices];
::memset(piCachingStamps,0x0,pMesh->mNumVertices*sizeof(unsigned int));
// allocate an empty output index buffer. We store the output
// indices in one large array. Since the number of triangles
// won't change the input faces can be reused. This is how we save
// thousands of redundant mini allocations for aiFace::mIndices
const unsigned int iIdxCnt = pMesh->mNumFaces*3;
unsigned int* const piIBOutput = new unsigned int[iIdxCnt];
unsigned int* piCSIter = piIBOutput;
// allocate the flag array to hold the information
// whether a face has already been emitted or not
std::vector abEmitted(pMesh->mNumFaces,false);
// dead-end vertex index stack
std::stack sDeadEndVStack;
// create a copy of the piNumTriPtr buffer
unsigned int* const piNumTriPtr = adj.mLiveTriangles;
const unsigned int* const piNumTriPtrNoModify = new unsigned int[pMesh->mNumVertices];
::memcpy(const_cast (piNumTriPtrNoModify),piNumTriPtr,
pMesh->mNumVertices * sizeof(unsigned int));
// get the largest number of referenced triangles
// and allocate the "candidate buffer"
unsigned int iMaxRefTris = 0;
{
const unsigned int* piCur = adj.mLiveTriangles;
const unsigned int* const piCurEnd = adj.mLiveTriangles+pMesh->mNumVertices;
for (;piCur != piCurEnd;++piCur)
iMaxRefTris = std::max(iMaxRefTris,*piCur);
}
unsigned int* piCandidates = new unsigned int[iMaxRefTris*3];
iCacheMisses = 0;
/** PSEUDOCODE for the algorithm
A = Build-Adjacency(I) Vertex-triangle adjacency
L = Get-Triangle-Counts(A) Per-vertex live triangle counts
C = Zero(Vertex-Count(I)) Per-vertex caching time stamps
D = Empty-Stack() Dead-end vertex stack
E = False(Triangle-Count(I)) Per triangle emitted flag
O = Empty-Index-Buffer() Empty output buffer
f = 0 Arbitrary starting vertex
s = k+1, i = 1 Time stamp and cursor
while f >= 0 For all valid fanning vertices
N = Empty-Set() 1-ring of next candidates
for each Triangle t in Neighbors(A, f)
if !Emitted(E,t)
for each Vertex v in t
Append(O,v) Output vertex
Push(D,v) Add to dead-end stack
Insert(N,v) Register as candidate
L[v] = L[v]-1 Decrease live triangle count
if s-C[v] > k If not in cache
C[v] = s Set time stamp
s = s+1 Increment time stamp
E[t] = true Flag triangle as emitted
Select next fanning vertex
f = Get-Next-Vertex(I,i,k,N,C,s,L,D)
return O
*/
int ivdx = 0;
int ics = 1;
int iStampCnt = this->configCacheDepth+1;
while (ivdx >= 0)
{
unsigned int icnt = piNumTriPtrNoModify[ivdx];
unsigned int* piList = adj.GetAdjacentTriangles(ivdx);
unsigned int* piCurCandidate = piCandidates;
// get all triangles in the neighborhood
for (unsigned int tri = 0; tri < icnt;++tri)
{
// if they have not yet been emitted, add them to the output IB
const unsigned int fidx = *piList++;
if (!abEmitted[fidx])
{
// so iterate through all vertices of the current triangle
const aiFace* pcFace = &pMesh->mFaces[ fidx ];
const unsigned int* const p2 = pcFace->mIndices+3;
for (unsigned int* p = pcFace->mIndices;p != p2;++p)
{
const unsigned int dp = *p;
// the current vertex won't have any free triangles after this step
if (ivdx != dp)
{
// append the vertex to the dead-end stack
sDeadEndVStack.push(dp);
// register as candidate for the next step
*piCurCandidate++ = dp;
// decrease the per-vertex triangle counts
piNumTriPtr[dp]--;
}
// append the vertex to the output index buffer
*piCSIter++ = dp;
// if the vertex is not yet in cache, set its cache count
if (iStampCnt-piCachingStamps[dp] > this->configCacheDepth)
{
piCachingStamps[dp] = iStampCnt++;
++iCacheMisses;
}
}
// flag triangle as emitted
abEmitted[fidx] = true;
}
}
// the vertex has now no living adjacent triangles anymore
piNumTriPtr[ivdx] = 0;
// get next fanning vertex
ivdx = -1;
int max_priority = -1;
for (unsigned int* piCur = piCandidates;piCur != piCurCandidate;++piCur)
{
register const unsigned int dp = *piCur;
// must have live triangles
if (piNumTriPtr[dp] > 0)
{
int priority = 0;
// will the vertex be in cache, even after fanning occurs?
unsigned int tmp;
if ((tmp = iStampCnt-piCachingStamps[dp]) + 2*piNumTriPtr[dp] <= this->configCacheDepth)
priority = tmp;
// keep best candidate
if (priority > max_priority)
{
max_priority = priority;
ivdx = dp;
}
}
}
// did we reach a dead end?
if (-1 == ivdx)
{
// need to get a non-local vertex for which we have a good
// chance that it is still in the cache ...
while (!sDeadEndVStack.empty())
{
unsigned int iCachedIdx = sDeadEndVStack.top();
sDeadEndVStack.pop();
if (piNumTriPtr[ iCachedIdx ] > 0)
{
ivdx = iCachedIdx;
break;
}
}
if (-1 == ivdx)
{
// well, there isn't such a vertex. Simply get the next
// vertex in input order and hope it is not too bad ...
while (ics < (int)pMesh->mNumVertices)
{
++ics;
if (piNumTriPtr[ics] > 0)
{
ivdx = ics;
break;
}
}
}
}
}
if (!DefaultLogger::isNullLogger())
{
char szBuff[128]; // should be sufficiently large in every case
float fACMR2 = (float)iCacheMisses / pMesh->mNumFaces;
::sprintf(szBuff,"Mesh %i | ACMR in: %f out: %f | ~%.1f%%",meshNum,fACMR,fACMR2,
((fACMR - fACMR2) / fACMR) * 100.f);
DefaultLogger::get()->info(szBuff);
}
// sort the output index buffer back to the input array
piCSIter = piIBOutput;
for (aiFace* pcFace = pMesh->mFaces; pcFace != pcEnd;++pcFace)
{
pcFace->mIndices[0] = *piCSIter++;
pcFace->mIndices[1] = *piCSIter++;
pcFace->mIndices[2] = *piCSIter++;
}
// delete temporary storage
delete[] piCachingStamps;
delete[] piIBOutput;
delete[] piCandidates;
delete[] piNumTriPtrNoModify;
}