Add information about Scalar::Util::blessed.

[p5sagit/p5-mst-13.2.git] / dump.c

diff --git a/dump.c b/dump.c
index 9d2a017..9d2595f 100644 (file)
--- a/dump.c
+++ b/dump.c
@@ -195,7 +195,7 @@ Perl_sv_peek(pTHX_ SV *sv)
        unref++;
     }
     else if (DEBUG_R_TEST && SvREFCNT(sv) > 1) {
-       Perl_sv_catpvf(aTHX_ t, "<%u>", SvREFCNT(sv));
+       Perl_sv_catpvf(aTHX_ t, "<%"UVuf">", (UV)SvREFCNT(sv));
     }
 
 
@@ -1044,15 +1044,24 @@ Perl_do_sv_dump(pTHX_ I32 level, PerlIO *file, SV *sv, I32 nest, I32 maxnest, bo
                }
             }
            PerlIO_putc(file, ')');
-           /* Now calculate quality wrt theoretical value */
+           /* The "quality" of a hash is defined as the total number of
+              comparisons needed to access every element once, relative
+              to the expected number needed for a random hash.
+
+              The total number of comparisons is equal to the sum of
+              the squares of the number of entries in each backet.
+              For a random hash of n keys into k backets, the expected
+              value is
+                               n + n(n-1)/2k
+           */
+
            for (i = max; i > 0; i--) { /* Precision: count down. */
                sum += freq[i] * i * i;
             }
            while ((keys = keys >> 1))
                pow2 = pow2 << 1;
-           /* Approximate by Poisson distribution */
            theoret = HvKEYS(sv);
-           theoret += theoret * theoret/pow2;
+           theoret += theoret * (theoret-1)/pow2;
            PerlIO_putc(file, '\n');
            Perl_dump_indent(aTHX_ level, file, "  hash quality = %.1"NVff"%%", theoret/sum*100);
        }