Re: [ppsp] [Spam] 回复: Re:回复: Re: Proposal to resolve Issue 10 + 13

[Arno Bakker <[e-mail]>]

On 18/04/2012 12:34, zhangyunfei wrote:
> Hi Arno，
> Pls see inline.Thanks.

Hi all

this landed in my spam box, so sorry for the late reply. See inline.

> [Yunfei] This is what I worry about. We cannot assure that each time we 
> can request
> chunks in groups of powers of 2, as it's dependent on what the serving 
> peers have, which
> is hard to ensure that the number of available chunks being powers of 2. 

IMHO, chunks will be requested in powers of 2. First, one will likely
request more than 1 chunk at a time to be able to fill the pipeline from
sender to receiver (cf. delay-bandwidth product). Requesting 1K and then
waiting for it will not be efficient. Second, as we're computer
scientists we'll use base 2 (32K, 64K, etc) when using multiples ;o)


> In such cases, requsting
> a range of chunks needs no more bits than bin number. What's worse, if 
> the chunks peer A has is
> sparsely distributed, i.e., the chunkmap is likely to be 10001011110, 
> bin numbering needs more bits.

Bins are actually more efficient than (start,end) in this example. With
bin numbers, you'll in the worst case need an integer for every 1 in the
bitmap, so 6 in this case. In a better case we might be able to address
the 4 ones at the end as a single bin. However, if you use (start,end)
addressing, you'll actually need 2 integers per 1 bit, or 12 integers.

CU,
    Arno