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How to design a class appropriate for millions of allocations?


By : SardaFilm
Date : October 14 2020, 11:12 PM
it helps some times I don't think there's much to say about designing your class for millions of allocations. Yes, there's the obvious memory limit, so if you have a fix amount of memory this might be a real concern for you, otherwise you will always risk running out of memory. A pointer to the virtual table is just that, a pointer (4 or 8 bytes on 32 or 64 bit architecture), not sure this is the case in multiple inheritance. Calling virtual functions has the overhead of the virtual lookup (and extra cache miss, if you didn't use it recently), but only for virtual functions, and they may never be inlined.
If there's a lot of repeated values, you might want to look into having a separate data structure as well (flyweight pattern). And for efficiency, make sure you have a light-weight (inlined) constructor and assignment operators, especially if you intend to use stl vectors and similar.
code :


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DB Design for high amount of data (20 millions rows / day)


By : user3250314
Date : March 29 2020, 07:55 AM
This might help you I see a couple of things you may want to consider.
1) message queue - to drop a log line and let other part (worker) of the system to take care of it when time permits

is having millions of tables and millions of rows within them a common practice in MySQL database design?


By : rontgen
Date : March 29 2020, 07:55 AM
To fix the issue you can do 1 - Definitely not. Almost anyone you ask will tell you millions of tables is a terrible idea.
2 - Millions of ROWS is common, so just fine.

How best to fill a vector of vectors (avoiding wasting memory and unnecessary allocations & de-allocations)?


By : BleepBloop
Date : March 29 2020, 07:55 AM
I hope this helps .
Q1 Will the copy (made inside push_back) have capacity() == size() (what I want), or preserve whatever tmp had, or is this implementation dependent / undefined?
code :
std::vector<std::vector<big_data_type> > table;
for(auto i=0; i!=4242; ++i) {
  std::vector<big_data_type> tmp = make_vector(i); // copy elison
  tmp.shrink_to_fit();                             // shrink
  table.push_back(std::move(tmp));                 // move
}
std::vector<std::vector<big_data_type> > table;
table.reserve(N);
std::vector<big_data_type> tmp;
for(auto i=0; i!=N; ++i) {
  tmp = make_vector(i); // #1
  table.push_back(tmp); // #2
}
// #3
std::vector<std::vector<big_data_type> > table;
table.reserve(N);
for(auto i=0; i!=N; ++i) {
  auto tmp = make_vector(i);          // #1
  tmp.shrink_to_fit();                // #2
  table.emplace_back(std::move(tmp)); // #3
}

Creating unwanted allocations/ failing to release allocations


By : user2884361
Date : March 29 2020, 07:55 AM
I wish this helpful for you If you malloc() memory you are (usually) responsible for latter calling free() to release it. However from the documentation for CGBitmapContextCreate:

Is there a custom memory allocator design pattern that does not store metadata in its allocations?


By : Dave
Date : March 29 2020, 07:55 AM
wish helps you If all your small allocations are the same size or have a reasonable upper bound, then a fixed size pool allocator is a good pattern.
The idea is that the allocator grabs a big block using the system call then manages its own free list of fixed size blocks within the big block. Allocation is as easy as taking the block at the head of the free list. Deallocation is a little more complicated but can be implemented in different ways depending on your requirements.
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