+ yaz_log(YLOG_LOG,"Normalizing client %d: scorefield=%d count=%d range=%f %f",
+ norm->num, norm->scorefield, norm->count, norm->min, norm->max);
+ norm->a = 1.0; // default normalizing factors, no change
+ norm->b = 0.0;
+ if ( norm->scorefield != scorefield_none &&
+ norm->scorefield != scorefield_position )
+ { // have something to normalize
+ double range = norm->max - norm->min;
+ int it = 0;
+ double a,b; // params to optimize
+ double as,bs; // step sizes
+ double chi;
+ char *branch = "?";
+ // initial guesses for the parameters
+ if ( range < 1e-6 ) // practically zero
+ range = norm->max;
+ a = 1.0 / range;
+ b = abs(norm->min);
+ as = a / 10;
+ bs = b / 10;
+ chi = squaresum( norm->records, a,b);
+ while (it++ < maxiterations) // safeguard against things not converging
+ {
+ double aplus = squaresum(norm->records, a+as, b);
+ double aminus= squaresum(norm->records, a-as, b);
+ double bplus = squaresum(norm->records, a, b+bs);
+ double bminus= squaresum(norm->records, a, b-bs);
+ double prevchi = chi;
+ if ( aplus < chi && aplus < aminus && aplus < bplus && aplus < bminus)
+ {
+ a = a + as;
+ chi = aplus;
+ as = as * (1.0 + stepchange);
+ branch = "aplus ";
+ }
+ else if ( aminus < chi && aminus < aplus && aminus < bplus && aminus < bminus)
+ {
+ a = a - as;
+ chi = aminus;
+ as = as * (1.0 + stepchange);
+ branch = "aminus";
+ }
+ else if ( bplus < chi && bplus < aplus && bplus < aminus && bplus < bminus)
+ {
+ b = b + bs;
+ chi = bplus;
+ bs = bs * (1.0 + stepchange);
+ branch = "bplus ";
+ }
+ else if ( bminus < chi && bminus < aplus && bminus < bplus && bminus < aminus)
+ {
+ b = b - bs;
+ chi = bminus;
+ branch = "bminus";
+ bs = bs * (1.0+stepchange);
+ }
+ else
+ { // a,b is the best so far, adjust one step size
+ // which one? The one that has the greatest effect to chi
+ // That is, the average of plus and minus is further away from chi
+ double adif = 0.5 * ( aplus + aminus ) - prevchi;
+ double bdif = 0.5 * ( bplus + bminus ) - prevchi;
+ if ( fabs(adif) > fabs(bdif) )
+ {
+ as = as * ( 1.0 - stepchange);
+ branch = "step a";
+ }
+ else
+ {
+ bs = bs * ( 1.0 - stepchange);
+ branch = "step b";
+ }
+ }
+ yaz_log(YLOG_LOG,"Fitting %s it=%d: a=%f %f b=%f %f chi=%f ap=%f am=%f, bp=%f bm=%f p=%f",
+ branch, it, a, as, b, bs, chi,
+ aplus, aminus, bplus, bminus, prevchi );
+ norm->a = a;
+ norm->b = b;
+ if ( fabs(as) * enough < fabs(a) &&
+ fabs(bs) * enough < fabs(b) ) {
+ break; // not changing much any more
+
+ }
+ }
+ yaz_log(YLOG_LOG,"Fitting done: it=%d: a=%f / %f b=%f / %f chi = %f",
+ it-1, a, as, b, bs, chi );
+ yaz_log(YLOG_LOG," a: %f < %f %d",
+ fabs(as)*enough, fabs(a), (fabs(as) * enough < fabs(a)) );
+ yaz_log(YLOG_LOG," b: %f < %f %d",
+ fabs(bs)*enough, fabs(b), (fabs(bs) * enough < fabs(b)) );