[DCCP] tfrc: Fix small error in reverse lookup of p for given f(p)
This fixes the following small error in tfrc_calc_x_reverse_lookup. 1) The table is generated by the following equations: lookup[index][0] = g((index+1) * 1000000/TFRC_CALC_X_ARRSIZE); lookup[index][1] = g((index+1) * TFRC_CALC_X_SPLIT/TFRC_CALC_X_ARRSIZE); where g(q) is 1E6 * f(q/1E6) 2) The reverse lookup assigns an entry in lookup[index][small] 3) This index needs to match the above, i.e. * if small=0 then p = (index + 1) * 1000000/TFRC_CALC_X_ARRSIZE * if small=1 then p = (index+1) * TFRC_CALC_X_SPLIT/TFRC_CALC_X_ARRSIZE These are exactly the changes that the patch makes; previously the code did not conform to the way the lookup table was generated (this difference resulted in a mean error of about 1.12%). Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
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net/dccp/ccids/lib
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@ -667,9 +667,9 @@ u32 tfrc_calc_x_reverse_lookup(u32 fvalue)
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ctr++;
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if (small)
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return TFRC_CALC_X_SPLIT * ctr / TFRC_CALC_X_ARRSIZE;
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return (ctr + 1) * TFRC_CALC_X_SPLIT / TFRC_CALC_X_ARRSIZE;
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else
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return 1000000 * ctr / TFRC_CALC_X_ARRSIZE;
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return (ctr + 1) * 1000000 / TFRC_CALC_X_ARRSIZE;
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}
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EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup);
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