1 // This file is part of meshoptimizer library; see meshoptimizer.h for version/license details 2 #include "meshoptimizer.h" 3 4 #include <assert.h> 5 #include <string.h> 6 meshopt_analyzeVertexFetch(const unsigned int * indices,size_t index_count,size_t vertex_count,size_t vertex_size)7meshopt_VertexFetchStatistics meshopt_analyzeVertexFetch(const unsigned int* indices, size_t index_count, size_t vertex_count, size_t vertex_size) 8 { 9 assert(index_count % 3 == 0); 10 assert(vertex_size > 0 && vertex_size <= 256); 11 12 meshopt_Allocator allocator; 13 14 meshopt_VertexFetchStatistics result = {}; 15 16 unsigned char* vertex_visited = allocator.allocate<unsigned char>(vertex_count); 17 memset(vertex_visited, 0, vertex_count); 18 19 const size_t kCacheLine = 64; 20 const size_t kCacheSize = 128 * 1024; 21 22 // simple direct mapped cache; on typical mesh data this is close to 4-way cache, and this model is a gross approximation anyway 23 size_t cache[kCacheSize / kCacheLine] = {}; 24 25 for (size_t i = 0; i < index_count; ++i) 26 { 27 unsigned int index = indices[i]; 28 assert(index < vertex_count); 29 30 vertex_visited[index] = 1; 31 32 size_t start_address = index * vertex_size; 33 size_t end_address = start_address + vertex_size; 34 35 size_t start_tag = start_address / kCacheLine; 36 size_t end_tag = (end_address + kCacheLine - 1) / kCacheLine; 37 38 assert(start_tag < end_tag); 39 40 for (size_t tag = start_tag; tag < end_tag; ++tag) 41 { 42 size_t line = tag % (sizeof(cache) / sizeof(cache[0])); 43 44 // we store +1 since cache is filled with 0 by default 45 result.bytes_fetched += (cache[line] != tag + 1) * kCacheLine; 46 cache[line] = tag + 1; 47 } 48 } 49 50 size_t unique_vertex_count = 0; 51 52 for (size_t i = 0; i < vertex_count; ++i) 53 unique_vertex_count += vertex_visited[i]; 54 55 result.overfetch = unique_vertex_count == 0 ? 0 : float(result.bytes_fetched) / float(unique_vertex_count * vertex_size); 56 57 return result; 58 } 59