[erlang-questions] Fast binary reverse

[Ward Bekker]

Hi Michael,


Yes, Funs will give overhead. Badly chosen example code on my part.


But still the rev2 example is on my machine still twice or trice as slow (YMMV) than a list:reverse. 


I want to see what can be done to bring a binary reverse on par with a list reverse. I would, naïvely, expect a binary reverse to be faster than a erlang list reverse.


Regards,


Ward



  _____  

From: Michael Uvarov [mailto:freeakk@REDACTED]
To: Ward Bekker [mailto:ward@REDACTED]
Sent: Thu, 27 Oct 2011 10:33:12 +0200
Subject: Re: [erlang-questions] Fast binary reverse

Just don't use anonymous functions.
  
  <code>
  -module(bin).
  -export([rev1/1, rev2/1]).
  
  
  rev1(B) ->
      S = size(B)*8,
      <<X:S/integer-little>>=B,
      <<X:S/integer-big>>.
  
  rev2(B) ->
      binary:list_to_bin(
          lists:reverse(
              binary:bin_to_list(B))).
  </code>
  
  
  29>  timer:tc(bin,rev2,[<<"teribly">>]).
  {5,<<"ylbiret">>}
  30>  timer:tc(bin,rev1,[<<"teribly">>]).
  {11,<<"ylbiret">>}
  
  --
  Best regards,
  Uvarov Michael
    
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