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-- This file is free software, which comes along with SmartEiffel. This
-- software is distributed in the hope that it will be useful, but WITHOUT
-- ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-- FITNESS FOR A PARTICULAR PURPOSE. You can modify it as you want, provided
-- this header is kept unaltered, and a notification of the changes is added.
-- You are allowed to redistribute it and sell it, alone or as a part of
-- another product.
--
-- Copyright(C) 1994-2002: INRIA - LORIA (INRIA Lorraine) - ESIAL U.H.P.
-- - University of Nancy 1 - FRANCE
-- Copyright(C) 2003: INRIA - LORIA (INRIA Lorraine) - I.U.T. Charlemagne
-- - University of Nancy 2 - FRANCE
--
-- Dominique COLNET, Suzanne COLLIN, Olivier ZENDRA,
-- Philippe RIBET, Cyril ADRIAN
--
-- http://SmartEiffel.loria.fr - SmartEiffel@loria.fr
--
expanded class HASH_TABLE_SIZE
--
-- Some useful features to deal with prime INTEGER values in order to
-- select an appropriate size for some hash table (used for example
-- by the DICTIONARY class as well as by the SET class).
--
feature
prime_number_ceiling(integer: INTEGER): INTEGER is
-- A good prime number, large enough, and no smaller than `integer'.
do
if integer <= 53 then
-- This seems to be a good minimum value to start hashing with.
Result := 53
elseif integer <= 97 then
Result := 97
elseif integer <= 193 then
Result := 193
elseif integer <= 389 then
Result := 389
elseif integer <= 769 then
Result := 769
elseif integer <= 1543 then
Result := 1543
elseif integer <= 3079 then
Result := 3079
elseif integer <= 6151 then
Result := 6151
elseif integer <= 12289 then
Result := 12289
elseif integer <= 24593 then
Result := 24593
elseif integer <= 49157 then
Result := 49157
elseif integer <= 98317 then
Result := 98317
elseif integer <= 196613 then
Result := 196613
elseif integer <= 393241 then
Result := 393241
elseif integer <= 786433 then
Result := 786433
elseif integer <= 1572869 then
Result := 1572869
elseif integer <= 3145739 then
Result := 3145739
elseif integer <= 6291469 then
Result := 6291469
elseif integer <= 12582917 then
Result := 12582917
elseif integer <= 25165843 then
Result := 25165843
elseif integer <= 50331653 then
Result := 50331653
elseif integer <= 100663319 then
Result := 100663319
elseif integer <= 201326611 then
Result := 201326611
elseif integer <= 402653189 then
Result := 402653189
elseif integer <= 805306457 then
Result := 805306457
else
Result := 1610612741
-- This should be enough !
end
ensure
Result >= integer
end
end
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