【发布时间】：2019-10-30 20:11:25
【问题描述】：
首先，对于糟糕的格式，我很抱歉，我是新手，知道我没有把它做得漂亮。
我正在实施一个系统来跟踪我以块形式存储的订单，但我还没有获得使用模板来完全理解参考文档的经验。 （我已尽我所能通读，并赢得了对 Joaquin 的极大尊重。似乎没有排名复合键的示例）
struct Block{//Variable types apart from the bool are immutable, values may be modified though
/*
This is to replace the previous lookup structure consisting of a map of buys and sells, to a map of products, to a map of prices, to a map of priorities, pointing to a struct holding the blockID and quantity
For a modify, if they are changing products or prices, it will create a new order, else they can shrink quantity desired without changing the priorityAtPrice
If they want to increase the quantity they lose their priority, but the order will keep the other values
*/
const int32_t productID; //One of ~20 different products
mutable uint32_t orderQuantity;//Number of products wanted at that price
const int64_t desiredPrice; //Prices are not unique
mutable uint64_t priorityAtPrice;//It's a global priority, in case someone alters their order
const uint64_t blockID;//Unique to every block
bool buy;//Tag to note if they are a looking to sell or buy
bool operator<(const Block& lilBlock)const{return blockID<lilBlock.blockID>}
};
struct idHash{
uint64_t operator()(const Block& lilBlock)const{
return lilBlock.blockID;
}
}
struct ObtainElementByBlockID {};
struct ObtainSublistByProductAndPrice {};
struct PlaceInLine {};
struct randomAccess {};
typedef boost::multi_index_container<
Block*,//Data type being stored, in this case, it is a pointer to Block.
//I'd like to store the block objects in an array[size uint64_t] indexed by the BlockIDs, since they are unique and will be accessed often, so keeping as much in cache is desirable
boost::multi_index::indexed_by<
boost::multi_index::hashed_unique<//Ideally should be fed an ID and retrieve the orderBlock in O(1) time
//It is never needed to compare IDs beyond checking if that is the ID being queried for
boost::multi_index::tag<ObtainElementByBlockID>
,boost::multi_index::member<Block,uint64_t, blockID>
,idHash
>
,boost::multi_index::random_access<
boost::multi_index::tag<randomAccess>
,boost::multi_index::member<Block,uint64_t,blockID>
>
,boost::multi_index::ordered_non_unique<//Should return a sublist at a product/price pair ordered by priorityAtPrice
boost::multi_index::tag<ObtainSublistByProductAndPrice>
,boost::multi_index::composite_key<
Block,
boost::multi_index::member<Block, int32_t, &Block::productID>
,boost::multi_index::member<Block, int64_t, &Block::desiredPrice>
,boost::multi_index::member<Block, uint64_t, &Block::priorityAtPrice>
>
,boost::multi_index::composite_key_compare<
std::equal<int32_t>
,std::equal<uint64_t>
,std::less<uint64_t>
>
>
/*
I think what I want has to do with rank
At product/price/buy, the value returned should be the sum of the quantities with a lower priority.
Say at [chairs, 5$, buy=true] there are orders(priority,quantity)
such that {(2,5),(6,12),(896, 3)}
with block IDs {753, 54, 712}
Querying for the place in line of a block, given the blockID 712
It should return 17, since there are orders ahead of block 712 with quantities 5+12=17
(It might actually need to return 18, but that's trivial)
*/
,boost::multi_index::ranked_non_unique<
boost::multi_index::tag<PlaceInLine>
,boost::multi_index::composite_key<
Block,
boost::multi_index::member<Block, int32_t, &Block::productID>
,boost::multi_index::member<Block, int64_t, &Block::desiredPrice>
,boost::multi_index::member<Block,priorityAtPrice>
>
,boost::multi_index::composite_key_compare<
std::equal<int32_t>
,std::equal<uint64_t>
,std::less<uint64_t>
>
>
> BlockDatabase;
我需要帮助确保我的 multi_index 格式正确。
附： - 任何有关能够从给定产品/价格中快速提取购买或销售数量总和的帮助将不胜感激。
【问题讨论】：
标签： c++ boost multi-index latency boost-multi-index