libsvm-284 源代码分析.doc

?libsvm-2.84 源代码分析（一）——cache类收藏 /*=============================================libsvm 2.84 代码分析 分析模块：cache类 分析者：ByronE-Mail: byronm@分析日期：2007年8月2日 ==============================================*///// Kernel Cache//// l is the number of total data items// size is the cache size limit in bytes//class Cache{public:?Cache(int l,long int size); ?//构建Cache的参数，包含l(数据个数)和size(空间大小)?????// l is the number of total data items?????// size is the cache size limit in bytes?~Cache();//析构函数 ?// request data [0,len)?// return some position p where [p,len) need to be filled?// (p = len if nothing needs to be filled)?int get_data(const int index, Qfloat **data, int len);//读取数据?void swap_index(int i, int j);?// future_optionprivate:?int l;?long int size; ?struct head_t???{??head_t *prev, *next;?// a cicular list 双向链表??Qfloat *data;??int len;??// data[0,len) is cached in this entry?}; ?head_t *head;????head_t lru_head;?void lru_delete(head_t *h);?void lru_insert(head_t *h);}; //cache保证索引结构的大小，余下的大小用来存放数据//size最后被修改为可以存放Qfloat类型数据的大小Cache::Cache(int l_,long int size_):l(l_),size(size_){?head = (head_t *)calloc(l,sizeof(head_t));?//initialized to 0，分配所有数据结构所需内存（地址连续）?size /= sizeof(Qfloat);????//Qfloat 类型的个数，（size 的 意义已经由数据空间大小变为数据个数）?size -= l * sizeof(head_t) / sizeof(Qfloat);?//除结构体所占用的空间外，剩下用于存放数据的个数?size = max(size, (long int) 2*l);??//cache must be large enough for two columns?lru_head.next = lru_head.prev = lru_head;} Cache::~Cache()//释放内存数据区，然后释放结构{?for(head_t *h = lru_head.next; h != lru_head; h=h-next)??free(h-data);?free(head);} void Cache::lru_delete(head_t *h){?// delete from current location?h-prev-next = h-next;?h-next-prev = h-prev;} //循环链表插入void Cache::lru_insert(head_t *h){?// insert to last position?h-next = lru_head;?h-prev = lru_head.prev;?h-prev-next = h;?h-next-prev = h;} // request data [0,len)// return some position p where [p,len) need to be filled // (p = len if nothing needs to be filled)?//返回cache的