On 14.03.2013 01:03, Daniel Shahaf wrote: > Branko Čibej wrote on Thu, Mar 14, 2013 at 00:43:24 +0100: >> On 14.03.2013 00:07, Bo Chen wrote: >>> Can anyone help me make clear this question? In SVN, if I have two >>> versions A and B. I compute a delta of B against A, i.e., I can >>> recover B by A and this delta. My question is, can I recover A by >>> using B and the same delta? >> No. It's theoretically possible to reverse a delta, but to do that, you >> must have both A and B available. > If you have A and B, you can just do (A-B) to get a reversed delta. > > Or maybe you mean that (A-B) can be computed more efficiently given > (A,B,B-A) than given (A,B)?
I believe it can be more efficient in terms of the cost for producing the inverse delta in some cases, but I never researched that in detail because its clear that the /size/ of such a delta would not be optimal. -- Brane -- Branko Čibej Director of Subversion | WANdisco | www.wandisco.com
