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plurals

POTemplates as an alternative to virtual functions in C++
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Id
9240168
data
AcceptedAnswerId
9240221
AnswerCount
2
ClosedDate
CommentCount
6
CommunityOwnedDate
CreationDate
2012-02-11T12:21:44.673
FavoriteCount
1
LastActivityDate
2012-02-11T14:37:45.480
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LastEditorUserId
0
OwnerUserId
1203683
ParentId
0
PostTypeId
1
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0
ViewCount
1170
LastEditorDisplayName
text
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I have an expensive function defined in a base class, which depends on low level information from its derived classes: <pre><code>class BaseClass{ ... // Defined in derived class virtual int low_level(int)=0; // Expensive function depending on the pure virtual function void myExpensiveFunction(){ for(...){ for(...){ for(...){ ... = low_level(...); ... } } } } }; class DerivedClass : public BaseClass{ // A very cheap operation that can be inlined: inline virtual int low_level(int i){ return a[i]; } // Calling the base class function void test(){ myExpensiveFunction(); } }; </code></pre> If I understand things correctly, the fact that the low-level function is virtual prevents it from being inlined in the code above. Now, I was thinking about a way to get around this and thought of the following solution, where I pass a pointer to the derived class member function as a template parameter: <pre><code>class BaseClass{ ... // The function is now templated by the derived function: template<typename D, int (D::*low_level)(int)> void myExpensiveFunction(){ for(...){ for(...){ for(...){ ... = static_cast<D*>(this)->low_level(...); ... } } } } }; class DerivedClass : public BaseClass{ // A very cheap operation that can be inlined: inline int low_level(int i){ return a[i]; } // Calling the base class function void test(){ myExpensiveFunction<DerivedClass,&DerivedClass::low_level>(); } }; </code></pre> Does this strategy make sense? I imagine that the low level operation will be inlined when the expensive base class function is expanded in the derived class. I tested implementing it and it compiles and works, but I haven't seen any noticeable differences in performance. Kind regards, Joel
Tags
<c++>
Title
Templates as an alternative to virtual functions in C++
singulars
PostAcceptedAnswerId
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
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1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. This table or related slice is empty.
UserOwnerUserId
1. USJoel
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PostLinksPostIdRelatedPostId
1. PL
 singulars
 LinkTypeLinkTypeId
 LTLinked
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
2. PO
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 PostTypePostTypeId
 PTAnswer
VotesPostIdCreationDate
1. VO
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 PostPostId
 POTemplates as an alternative to virtual functions in C++
 UserUserId
 USEddy Pronk
 VoteTypeVoteTypeId
 VTFavorite
CommentsPostId

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