Re: [boost] [Block Pointer] Up to 600% faster than Shared Pointer

Subject: Re: [boost] [Block Pointer] Up to 600% faster than Shared Pointer
From: Phil Bouchard (philippeb8_at_[hidden])
Date: 2016-03-13 11:14:02

On 03/13/2016 12:00 AM, Glen Fernandes wrote:
> On Sat, Mar 12, 2016 at 10:12 PM, Phil Bouchard wrote:
>> On 03/12/2016 09:22 PM, Glen Fernandes wrote:
>>>
>>> To add to our earlier discussion, you should also include the
>>> benchmark for allocate_shared() with fast_pool_allocator.
>>>
>>
>>
>> Good point, I was not aware it could be used this way.  I just added
>> fast_pool_allocator<>() to the benchmark so now the comparison is fair and
>> block_ptr<> still is faster by 125%:
>
> Hi Phil,
>
> The other thing I observed in your benchmarks is the distinction
> between 'new T' and 'new T()'. i.e. make_shared() and
> allocate_shared() (and make_unique() too) all value-initialize. 'new
> T' (and T is 'int' in your example) is default-initialization (while
> 'new T()' would be value-initialization).
>
> You can use boost::make_shared_noinit() and
> boost::allocate_shared_noinit() (and boost::make_unique_noinit() also)
> if you want default-initialization. Or you can use 'new T()' instead
> of 'new T' and have value-initialization.

There is not much difference, now block_ptr<> is still 132% faster than 
shared_ptr<>:

make:
auto_ptr:                   25564043 ns
shared_ptr:                 26421429 ns

make alloc:
shared_ptr:                 11725542 ns

make alloc noinit:
shared_ptr:                 11665724 ns <-

new:
auto_ptr:                   23546857 ns
shared_ptr:                 49000954 ns
block_ptr:                   8791379 ns <-

> (I haven't looked at the implementation of block_ptr yet, or the
> design, or the purpose of it, I just saw the thread on benchmarks and
> examined your benchmark program source).

I keep cleaning up the code and now I think it is very easy to understand:

proxy_ptr<node> x;
block_ptr<node> v = block_ptr<node>(x, new block<node>(x));
v->next = v;

You have 2 types of pointers: proxy_ptr<> and block_ptr<>.  proxy_ptr<> 
is the root of the tree block_ptr<> will build on.  When proxy_ptr<> 
gets deleted then all block_ptr<> associated to it will be wiped out as 
well.  The purpose of block_ptr<> is to delete cyclic pointers.