From: Gerrit Renker Date: Sun, 3 Dec 2006 16:52:01 +0000 (-0200) Subject: [DCCP] tfrc: Fix small error in reverse lookup of p for given f(p) X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=90fb0e60dd9178dbca2e42c682c483cdb7ea9f2d;p=openwrt%2Fstaging%2Fblogic.git [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 Acked-by: Ian McDonald Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/net/dccp/ccids/lib/tfrc_equation.c b/net/dccp/ccids/lib/tfrc_equation.c index 57665e979308..78bdf3489162 100644 --- a/net/dccp/ccids/lib/tfrc_equation.c +++ b/net/dccp/ccids/lib/tfrc_equation.c @@ -667,9 +667,9 @@ u32 tfrc_calc_x_reverse_lookup(u32 fvalue) ctr++; if (small) - return TFRC_CALC_X_SPLIT * ctr / TFRC_CALC_X_ARRSIZE; + return (ctr + 1) * TFRC_CALC_X_SPLIT / TFRC_CALC_X_ARRSIZE; else - return 1000000 * ctr / TFRC_CALC_X_ARRSIZE; + return (ctr + 1) * 1000000 / TFRC_CALC_X_ARRSIZE; } EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup);