From: Rainer Deyke (rainerd_at_[hidden])
Date: 2008-08-29 16:53:28
troy d. straszheim wrote:
> Rainer Deyke wrote:
>> I don't think performance should be the overriding concern, especially
>> since byte-shuffling is very fast.
>
> But it isn't fast.
It is when compared to the overhead of IO (disk or socket, possibly even
memory).
> If the necessity of bitshuffling makes it impossible to
> serialize, say a vector<double> via the optimized array handling, you
> could easily be talking about a factor of 10 in speed.
I think here you are talking about the overhead of a single write
operation versus multiple write operations on the underlying stream,
correct?
It's true that the standard stream operations can be slow, but that is a
separate problem from the actual byte shuffling and should be solved
separately. Maybe this problem could be avoided by using a
std::vector<char> instead of a stream object for the actual
serialization and then dumping it all at once.
(It is not reasonable to just dump in-memory objects to a stream in any
portable format, binary or text.)
> The problem with option 3 is that it introduces a potential source of
> > bugs that only manifests when moving
>> between platforms with different endianness. I'd prefer option 1,
>> precisely because it requires shuffling on the most common platforms
>> so any bugs in the shuffling code are sure to be caught early.
>
> Actually this is very easy to test for, even if you don't have machines
> of the
> other endianness available. (the md5sum of the generated archive must
> match
> for all platforms, and these sums can be checked in to svn)
I though option 3 was to write little-endian archives on little-endian
machines and big-endian archives on big-endian machines? If so, the
generated archives would /not/ be the same. Hence the potential source
of bugs.
-- Rainer Deyke - rainerd_at_[hidden]