[mnet-devel] FEC performance again

[Zooko]

Err.. hey waitasecond!  What were those numbers I posted?

Here are the times to encode a 256 MB file with different share sizes:

share size      num shares      time (secs)
----------      ----------      -----------
      2 MB             128              283
      4 MB              64              142
      8 MB              32               72
     16 MB              16               37
     32 MB               8               19
     64 MB               4               14
    128 MB               2               29
    256 MB               1               48

That's for a 256 MB file with 2x redundancy, so to store it on Mnet would 
require that you transfer (about) 512 MB.  So even if you generate 128 shares 
required (256 shares total), where each share is 2 MB, then you are generating 
1.8 MB/sec.

That's pretty good.

We may have been thinking that one has to wait all 283 seconds and *then* 
begin storing the file onto the Mnet filespace, but that's wrong.  Rizzo's 
fec.c and Myers's fecmodule.c are designed so that you generate one share at a 
time, which means we can be publishing the first share to blockservers right 
away.

--Z



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