Developer Documentation

GPUCacheOptimizer.cc
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40 \*===========================================================================*/
41
42
43 #include "GPUCacheOptimizer.hh"
44 #include <cassert>
45 #include <cmath>
46 #include <vector>
47 #include <cstring>
48
49 //=============================================================================
50
51 namespace ACG
52 {
53
54 //=============================================================================
55
56 GPUCacheOptimizer::GPUCacheOptimizer( unsigned int NumTris, unsigned int NumVerts, unsigned int IndexSize, const void* pIndices) :
57 m_NumVerts(NumVerts),
58 m_NumTris(NumTris),
59 m_IndexSize(IndexSize),
60 m_pIndices(pIndices),
61 m_NumTransformations(0)
62 {
63 m_pTriMap = new unsigned int[m_NumTris];
64 }
65
66 GPUCacheOptimizer::~GPUCacheOptimizer(void)
67 {
68 delete [] m_pTriMap;
69 }
70
71 //=============================================================================
72
73 unsigned int GPUCacheOptimizer::GetIndex(unsigned int i) const
74 {
75 assert(i < m_NumTris * 3);
76
77 return GetIndex(i, m_IndexSize, m_pIndices);
78 }
79
80 unsigned int GPUCacheOptimizer::GetIndex(unsigned int i, unsigned int IndexSize, const void* pIB)
81 {
82 switch (IndexSize)
83 {
84 case 4: return ((const unsigned int*)pIB)[i]; break;
85 case 2: return ((const unsigned short*)pIB)[i]; break;
86 case 1: return ((const unsigned char*)pIB)[i]; break;
87 default:
88 assert(i == 1 || i == 2 || i == 4); // throw error
89 }
90 return 0xFFFFFFFF;
91 }
92
93 void GPUCacheOptimizer::SetIndex(unsigned int i, unsigned int val, unsigned int IndexSize, void* pIB)
94 {
95 switch (IndexSize)
96 {
97 case 4: ((unsigned int*)pIB)[i] = val; break;
98 case 2: ((unsigned short*)pIB)[i] = val; break;
99 case 1: ((unsigned char*)pIB)[i] = val; break;
100 default:
101 assert(i == 1 || i == 2 || i == 4); // throw error
102 }
103 }
104
105 //=============================================================================
106
107 void GPUCacheOptimizer::WriteIndexBuffer(unsigned int DstIndexSize, void* pDst)
108 {
109 assert(DstIndexSize == 1 ||DstIndexSize == 2 || DstIndexSize == 4);
110 // TODO: warning log, if DstIndexSize < m_IndexSize
111
112 // support for 'in-place' operation via tmpbuf copy
113 char* pSrc = (char*)m_pIndices;
114
115 int bTmpCopy = 0;
116 if (pDst == pSrc)
117 {
118 pSrc = new char[m_IndexSize * m_NumTris * 3];
119 memcpy(pSrc, m_pIndices, m_IndexSize * m_NumTris * 3);
120
121 bTmpCopy = 1;
122 }
123
124 for (unsigned int i = 0; i < m_NumTris; ++i)
125 {
126 for (int k = 0; k < 3; ++k)
127 {
128 unsigned int TriVertex = GetIndex(m_pTriMap[i] * 3 + k, m_IndexSize, pSrc);
129
130 // copy remapped tri indices
131 SetIndex(i * 3 + k, TriVertex, DstIndexSize, pDst);
132 }
133 }
134
135 if (bTmpCopy) delete [] pSrc;
136 }
137
138 //=============================================================================
139
140 void GPUCacheOptimizer::RemapVertices(unsigned int NumTris, unsigned int NumVerts,
141 const unsigned int* pVertMap,
142 unsigned int IndexSize, void* pInOutIndices,
143 unsigned int VertexStride, void* pInOutVertices)
144 {
145 if (pVertMap && pInOutIndices && pInOutVertices && VertexStride)
146 {
147 // make tmp vertex buffer copy
148 char* pTmpBuf = new char[VertexStride * NumVerts];
149 memcpy(pTmpBuf, pInOutVertices, VertexStride * NumVerts);
150
151 char* pVertexOut = (char*)pInOutVertices;
152
153 // apply on vertex buffer
154
155 for (unsigned int i = 0; i < NumVerts; ++i)
156 {
157 // some mapping destinations might be invalid
158 // this vertex is unused, ignore then
159 if (pVertMap[i] < NumVerts)
160 memcpy(pVertexOut + pVertMap[i] * VertexStride,
161 pTmpBuf + i * VertexStride, VertexStride);
162 }
163
164 // apply on index buffer
165
166 for (unsigned int i = 0; i < NumTris * 3; ++i)
167 {
168 // IndexBuffer[i] = VertMap[IndexBuffer[i]]
169
170 unsigned int v = GetIndex(i, IndexSize, pInOutIndices);
171 SetIndex(i, pVertMap[v], IndexSize, pInOutIndices);
172 }
173
174 delete [] pTmpBuf;
175 }
176 }
177
178 //=============================================================================
179
180 void GPUCacheOptimizer::OptimizeVertices(unsigned int NumTris, unsigned int NumVerts,
181 unsigned int IndexSize, const void* pIndices,
182 unsigned int* pVertMap)
183 {
184 // straight forward algorithm
185 // simply iterate over indices and increment vertex location if unvisited vertex found
186 unsigned int uCounter = 0; // vertex counter
187
188 memset(pVertMap, 0xFF, NumVerts * sizeof(unsigned int));
189
190 for (unsigned int i = 0; i < NumTris * 3; ++i)
191 {
192 unsigned int vertex;
193
194 if (IndexSize == 2) vertex = ((const unsigned short*)pIndices)[i];
195 else vertex = ((const unsigned int*)pIndices)[i];
196
197 if (pVertMap[vertex] == 0xFFFFFFFF)
198 pVertMap[vertex] = uCounter++;
199 }
200 }
201
202 //=============================================================================
203
204 unsigned int GPUCacheOptimizer::ComputeNumberOfVertexTransformations(unsigned int VertexCacheSize)
205 {
206 if (m_NumTransformations) return m_NumTransformations;
207
208 unsigned int NumIndices = 3 * m_NumTris;
209 if (!NumIndices) return 0;
210
211 unsigned int* Cache = new unsigned int[VertexCacheSize];
212 unsigned int NumSlotsInUse = 0;
213 unsigned int LastSlot = 0;
214 m_NumTransformations = 0;
215
216 for (unsigned int i = 0; i < m_NumTris; ++i)
217 {
218 unsigned int t = m_pTriMap[i];
219
220 // for each vertex of triangle t:
221 for (int k = 0; k < 3; ++k)
222 {
223 unsigned int Idx = GetIndex(t * 3 + k); // vertex index
224
225 int bInCache = 0;
226 for (unsigned int k = 0; k < NumSlotsInUse && !bInCache; ++k)
227 {
228 if (Cache[k] == Idx) bInCache = 1;
229 }
230
231 if (!bInCache)
232 {
233 ++m_NumTransformations;
234 if (NumSlotsInUse < VertexCacheSize)
235 {
236 Cache[NumSlotsInUse++] = Idx;
237 ++LastSlot;
238 }
239 else
240 {
241 if (LastSlot == VertexCacheSize) LastSlot = 0;
242 Cache[LastSlot++] = Idx;
243 }
244 }
245 }
246
247 }
248
249 delete [] Cache;
250
251 return m_NumTransformations;
252 }
253
254 //=============================================================================
255
256 float GPUCacheOptimizer::ComputeACMR(unsigned int VertexCacheSize)
257 {
258 unsigned int NumT = ComputeNumberOfVertexTransformations(VertexCacheSize);
259 return float(NumT) / float(m_NumTris);
260 }
261
262 //=============================================================================
263
264 float GPUCacheOptimizer::ComputeATVR(unsigned int VertexCacheSize)
265 {
266 unsigned int NumT = ComputeNumberOfVertexTransformations(VertexCacheSize);
267 return float(NumT) / float(m_NumVerts);
268 }
269
270 //=============================================================================
271
272 // forsyth's score function
273 void GPUCacheOptimizer::Opt_Vertex::FindScore(unsigned int MaxSizeVertexCache)
274 {
275
276
277
278 float fNewScore = -1.0f; // -1 : vertex unused
279 if (iNumTrisLeft > 0)
280 {
281 if (iCachePos < 0) fNewScore = 0.0f; // not in FIFO
282 else
283 {
284
285 if (iCachePos < 3){ // last tri => fixed score
286
287 const float LastTriScore = 0.75f;
288 fNewScore = LastTriScore;
289
290 } else
291 {
292 const float CacheDecayPower = 1.5f;
293
294 // check for cache_pos < MaxSizeCachePos here..
295 // Points for being high in the cache.
296 const float Scaler = 1.0f / (MaxSizeVertexCache - 3);
297 fNewScore = 1.0f - ( iCachePos - 3 ) * Scaler;
298 fNewScore = powf( fNewScore, CacheDecayPower);
299 }
300 }
301
302 // Bonus points for having a low number of tris still to
303 // use the vert, so we get rid of lone verts quickly.
304
305 const float ValenceBoostScale = 2.0f;
306 const float ValenceBoostPower = 0.5f;
307
308 float ValenceBoost = powf( float(iNumTrisLeft), -float(ValenceBoostPower));
309 fNewScore += ValenceBoostScale * ValenceBoost;
310 }
311
312 fScore = fNewScore;
313 }
314
315 void GPUCacheOptimizer::Opt_Vertex::RemoveTriFromList(unsigned int tri)
316 {
317 for (int k = 0; k < iNumTrisLeft; ++k)
318 {
319 // replace tri with last tri in this list
320 if (pTris[k] == tri)
321 {
322 pTris[k] = pTris[iNumTrisLeft-1];
323 break;
324 }
325 }
326 --iNumTrisLeft;
327 }
328
329 //=============================================================================
330 // tipsify
331
332 GPUCacheOptimizerTipsify::GPUCacheOptimizerTipsify(unsigned int CacheSize, unsigned int NumTris, unsigned int NumVerts, unsigned int IndexSize, const void *pIndices)
333 : GPUCacheOptimizer(NumTris, NumVerts, IndexSize, pIndices)
334 {
335 // optimization notes:
336 // - cache unfriendly layout of Opt_Vertex: high read/write access cost to Opt_vertex data
337
338 if (NumVerts < 3 || !NumTris) return;
339
340 Opt_Vertex* pVerts = new Opt_Vertex[NumVerts];
341 Opt_Tris* pTris = new Opt_Tris[NumTris];
342
343 // OPTIMIZATION: memset vs constructor initialization: memset - 400 ms, constructor - 770 ms (at 10 mil vertices)
344 memset(pVerts, 0, sizeof(Opt_Vertex) * NumVerts);
345
346 // build adjacency, same start as in forsyth class
347 for (unsigned int i = 0; i < NumTris; ++i)
348 {
349 // copy vertex indices of this tri
350 Opt_Tris* pThisTri = pTris + i;
351
352 // copy vertex indices of this tri
353 for (unsigned int k = 0; k < 3; ++k)
354 {
355
356 const unsigned int idx = GetIndex(i * 3 + k);
357 pThisTri->v[k] = idx;
358
359 // count # tris per vertex
360 ++pVerts[idx].iNumTrisTotal;
361 }
362 }
363
364 // OPTIMIZATION: allocate one buffer for the complete vertex adjacency list (instead of allocating a new buffer for each vertex)
365 const unsigned int vertexTriAdjBufSize = NumTris * 3;
366 unsigned int vertexTriAdjBufOffset = 0;
367 unsigned int* vertexTriAdjBuf = new unsigned int[vertexTriAdjBufSize];
368
369 // create list of tris per vertex
370 for (unsigned int i = 0; i < NumTris; ++i)
371 {
372 // add this tri to per vertex tri list
373 for (int k = 0; k < 3; ++k)
374 {
375 Opt_Vertex* pV = pVerts + pTris[i].v[k];
376 if (!pV->pTris) {
377 pV->pTris = vertexTriAdjBuf + vertexTriAdjBufOffset;
378 vertexTriAdjBufOffset += pV->iNumTrisTotal;
379 }
380
381 // abuse <numTrisLeft> as temporal up counter
382 // (automatically sums to numTris, exactly what we want)
383 pV->pTris[pV->iNumTrisLeft++] = i;
384
385 pV->iCachePos = 0;
386 }
387 }
388
389 // use the cache_pos of the OptFaces_Vertex as the time stamp
390
391 //=============================================================================
392 // OPTIMIZATION:
393 // push and pop on DeadEndVertexStack greatly increases processing time
394 // -> replace with fixed size ring stack
395 // std::vector<unsigned int> DeadEndVertexStack;
396 // DeadEndVertexStack.reserve(2048);
397 RingStack DeadEndVertexStack(128);
398
399
400 int f = 0; // arbitrary starting index (vertex)
401 int iTimeStamp = CacheSize + 1;
402 unsigned int i = 1; // cursor
403
404 unsigned int numTrisAdded = 0;
405
406 std::vector<unsigned int> N; // 1-ring of next candidates
407 N.reserve(2048);
408
409 while (f >= 0)
410 {
411 N.clear();
412
413 // this vertex
414 Opt_Vertex* pV = pVerts + f;
415
416 // for each adjacent tri of this vertex
417 for (int m = 0; m < pV->iNumTrisTotal; ++m)
418 {
419 Opt_Tris* pT = pTris + pV->pTris[m];
420
421 if (!pT->bAdded)
422 {
423 // append
424 m_pTriMap[numTrisAdded++] = pV->pTris[m];
425
426 for (int k = 0; k < 3; ++k)
427 {
428 // push to cache
429 const unsigned int v = pT->v[k];
430 // DeadEndVertexStack.push_back(pT->v[k]);
431 DeadEndVertexStack.push(v);
432
433 // insert
434 N.push_back(v);
435
436 Opt_Vertex* adjV = pVerts + v;
437
438 --adjV->iNumTrisLeft;
439
440 if (iTimeStamp - adjV->iCachePos > (int)CacheSize)
441 adjV->iCachePos = iTimeStamp++;
442 }
443 pT->bAdded = 1;
444 }
445 }
446
447
448 // select next fanning vertex
449 // Get-Next-Vertex
450 {
451 int n = -1, p = -1; // best candidate and priority
452 for (unsigned int k = 0; k < N.size(); ++k)
453 {
454 // for each vertex in N
455 Opt_Vertex* pV = pVerts + N[k];
456
457 if (pV->iNumTrisLeft > 0)
458 {
459 // error here in pseudo code:
460 // literal p should be named m here
461 // to find the best vertex
462 int m = 0;
463 if (iTimeStamp - pV->iCachePos + 2 * pV->iNumTrisLeft <= (int)CacheSize)
464 m = iTimeStamp - pV->iCachePos;
465
466 if (m > p)
467 {
468 p = m;
469 n = N[k];
470 }
471 }
472 }
473
474 if (n == -1)
475 {
476 // Skip-Dead-End
477 while (DeadEndVertexStack.length() && (n == -1))
478 {
479 // unsigned int d = DeadEndVertexStack.back();
480 // DeadEndVertexStack.pop_back();
481 const unsigned int d = DeadEndVertexStack.pop();
482
483 if (pVerts[d].iNumTrisLeft > 0)
484 n = d;
485 }
486
487 while (i+1 < NumVerts && (n == -1))
488 {
489 ++i;
490 if (pVerts[i].iNumTrisLeft > 0)
491 n = i;
492 }
493 }
494
495 f = n;
496 }
497 }
498
499 // debugging purpose
500 // int capac = N.capacity();
501 // capac = DeadEndVertexStack.capacity();
502
503 delete [] vertexTriAdjBuf;
504
505 delete [] pVerts;
506 delete [] pTris;
507 }
508
509 //=============================================================================
510
511 GPUCacheEfficiencyTester::GPUCacheEfficiencyTester(unsigned int NumTris, unsigned int NumVerts,
512 unsigned int IndexSize, const void* pIndices)
513 : GPUCacheOptimizer(NumTris, NumVerts, IndexSize, pIndices)
514 {
515 for (unsigned int i = 0; i < NumTris; ++i) m_pTriMap[i] = i;
516 }
517
518 //=============================================================================
519
520
521 }
ACG::GPUCacheOptimizer::Opt_Vertex::FindScore
void FindScore(unsigned int MaxSizeVertexCache)
forsyth&#39;s score function
Definition: GPUCacheOptimizer.cc:273
ACG::GPUCacheOptimizer::Opt_Vertex::iNumTrisTotal
int iNumTrisTotal
tris using this vertex
Definition: GPUCacheOptimizer.hh:215
ACG
Namespace providing different geometric functions concerning angles.
Definition: BaseObjectData.hh:68
ACG::GPUCacheOptimizer::Opt_Tris
Definition: GPUCacheOptimizer.hh:226
ACG::GPUCacheOptimizer::OptimizeVertices
static void OptimizeVertices(unsigned int NumTris, unsigned int NumVerts, unsigned int IndexSize, const void *pIndices, unsigned int *pVertMap)
Reorders vertex buffer to minimize memory address jumps.
Definition: GPUCacheOptimizer.cc:180
ACG::GPUCacheOptimizer::RemapVertices
static void RemapVertices(unsigned int NumTris, unsigned int NumVerts, const unsigned int *pVertMap, unsigned int IndexSize, void *pInOutIndices, unsigned int VertexStride, void *pInOutVertices)
Applies the remap table of OptimizeVertices to a vertex and index buffer.
Definition: GPUCacheOptimizer.cc:140
ACG::GPUCacheOptimizerTipsify::GPUCacheOptimizerTipsify
GPUCacheOptimizerTipsify(unsigned int CacheSize, unsigned int NumTris, unsigned int NumVerts, unsigned int IndexSize, const void *pIndices)
The actual computation happens here in this constructor.
Definition: GPUCacheOptimizer.cc:332
ACG::GPUCacheOptimizer
Definition: GPUCacheOptimizer.hh:64
ACG::GPUCacheOptimizer::ComputeATVR
float ComputeATVR(unsigned int VertexCacheSize=16)
Measures the efficiency use of the vertex cache. ATVR: Average Transform to Vertex Ratio similar to A...
Definition: GPUCacheOptimizer.cc:264
ACG::GPUCacheOptimizer::WriteIndexBuffer
void WriteIndexBuffer(unsigned int DstIndexSize, void *pDst)
Applies the remapping on the initial pIndices constructor&#39;s param and stores the result in the given ...
Definition: GPUCacheOptimizer.cc:107
ACG::GPUCacheOptimizer::Opt_Tris::v
unsigned int v[3]
vertices of this triangle
Definition: GPUCacheOptimizer.hh:235
ACG::GPUCacheOptimizer::Opt_Vertex::iNumTrisLeft
int iNumTrisLeft
tris left to add to final result
Definition: GPUCacheOptimizer.hh:217
ACG::GPUCacheOptimizer::m_pTriMap
unsigned int * m_pTriMap
Definition: GPUCacheOptimizer.hh:192
ACG::GPUCacheOptimizerTipsify::RingStack::length
unsigned int length() const
current stack length
Definition: GPUCacheOptimizer.hh:318
ACG::GPUCacheOptimizer::ComputeNumberOfVertexTransformations
unsigned int ComputeNumberOfVertexTransformations(unsigned int VertexCacheSize=16)
Returns the total number of vertex transforms performed with a certain VertexCache.
Definition: GPUCacheOptimizer.cc:204
ACG::GPUCacheOptimizer::ComputeACMR
float ComputeACMR(unsigned int VertexCacheSize=16)
Measures the efficiency use of the vertex cache. ACMR: Average Cache Miss Ratio.
Definition: GPUCacheOptimizer.cc:256
ACG::GPUCacheOptimizerTipsify::RingStack
Simple and fast fixed size stack used in tipsify implementation.
Definition: GPUCacheOptimizer.hh:277
ACG::GPUCacheOptimizer::Opt_Vertex
Definition: GPUCacheOptimizer.hh:207