performance - Fastest type to use for comparing hashes in matlab -


i have table in matlab columns representing 128 bit hashes.

i match rows, 1 or more rows, based on these hashes.

currently, hashes represented hexadecimal strings, , compared strcmp(). still, takes many seconds process table.

what fastest way compare 2 hashes in matlab?

i have tried turning them categorical variables, slower. matlab far know not have 128 bit numerical type. nominal , ordinal types deprecated.

are there others work?

the code below analogous doing:

nodetype = { 'type1'; 'type2'; 'type1'; 'type2' }; hash = {'d285e87940fb9383ec5e983041f8d7a6'; 'd285e87940fb9383ec5e983041f8d7a6'; 'ec9add3cf0f67f443d5820708adc0485'; '5dbdfa232b5b61c8b1e8c698a64e1cc9' };  entries = table(categorical(nodetype),hash,'variablenames',{'type','hash'});  %nodes match. filter type or other way rows don't match %themselves. = entries(entries.type=='type1',:); b = entries(entries.type=='type2',:);  %pick node/row hash find counterparts of row_to_match_in_a = a(1,:); matching_rows_in_b = b(strcmp(b.hash,row_to_match_in_a.hash),:);  % stuff matching rows... disp(matching_rows_in_b);

the hash strings faithful representations of using, not read or stored strings in original source. converted purpose because fastest way comparison.

optimization nice, if need it. try out , measure performance gain relevant test cases.

some suggestions:

  • sorted arrays easier/faster search

  • matlab's default numbers double, but can construct integers. why not use 2 uint64's instead of 128bit column? first search upper 64bit, lower; or better: use ismember row option , put hashes in rows:

    a = uint64([0 0;             0 1;             1 0;             1 1;             2 0;             2 1]); srch = uint64([1 1;                0 1]); [ismatch, loc] = ismember(srch, a, 'rows')         > loc =      4      2

  • look compare functions use (eg edit ismember) , strip out unnecessary operations (eg sort) , safety checks know in advance won't pose problem. like solution does. or if intend call search function multiple times, sort in advance , skip check/sort in search function later on.


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