Problem with Vector/Shared Pointer

**Raigne** · 01-07-2009

I started using boost::shared_ptr to handle my pointer, then after applying it to my resource manager I realized I was losing a lot of performance in initialization, and shutdown was taking 10x as long to release my memory. So, I decided to make a test program to see what was happening, and I still can't figure it out. I am assuming it has something to do with the vector, but I am not sure.

Here is the test program to test speed. On release build it allocates 79,000k in task manager in about 3 seconds, and it takes my computer about 2 minutes to free it.
I am hoping someone can help me solve this issue. If not shared_ptr just isnt going to work for me.

Code:

template<class T>
struct SPtr
{
    typedef boost::shared_ptr<T> Type;
};

int main()
{
    std::vector<SPtr<int>::Type> Test;
    Test.resize(1000000);
    std::vector<SPtr<int>::Type>::iterator it = Test.begin();
    int x = 0;
    for ( ; it != Test.end(); ++it )
    {
        (*it).reset(new int(x));
        ++x;
    }
    system("pause");
    return 0;
}

Thank you for any assistance.

**anon** · 01-08-2009

Don't know. It takes slightly less time to free it for me and both happens in less than a second.

Did you also compare it against plain pointers?

Also, testing it with the simplest built-in type seems not very realistic: in real life the things you'd allocate dynamically would be more complex.

You might try profiling the code to see where it is slow.

**Raigne** · 01-08-2009

>>Also, testing it with the simplest built-in type seems not very realistic: in real life the things you'd allocate dynamically would be more complex.

Maybe so, but if it takes forever allocating/de-allocating built in data types, then naturally it will take even longer to do so with larger datatypes.

I am using VS C++ 9.0 sp1. Is there something with VS vector that makes it slow? ( such as debug stuff ) speed doesn't change from debug to release build.

I tried it with raw pointers (no vector/shared_ptr) and it is instantaneous .023 seconds. So, it has to be the vector I am assuming. I get a heap corruption error when creating a dynamic array of shared_ptr's.

I have been adding counters in my code that produce a message box with allocation/de-allocation times on different elements, and the speeds are ridiculous. 3 seconds to load 100 textures. approx. 10mb of data. Which with raw pointers is unnoticeable. ( This is not due to file streams. All data is contiguous in a single file. )

**C_ntua** · 01-08-2009

I believe there is bound checking for vectors in Visual C++. Don't know if this is not done in release mode. Don't know how to turn it off.

**laserlight** · 01-08-2009

Originally Posted by Raigne

I tried it with raw pointers (no vector/shared_ptr) and it is instantaneous .023 seconds. So, it has to be the vector I am assuming. I get a heap corruption error when creating a dynamic array of shared_ptr's.

The combination of shared_ptrs with vector might or might not be the problem, but boost::ptr_vector provides an alternative that might perform better.

Originally Posted by C_ntua

I believe there is bound checking for vectors in Visual C++. Don't know if this is not done in release mode. Don't know how to turn it off.

The bounds checking is enabled in the default release configuration as well, but can be disabled by setting _SECURE_SCL=0

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