New, better hash for floating point and complex

diff --git a/Objects/complexobject.c b/Objects/complexobject.c
index 175933a514e7a04f3ed8530d901ffa2902fd327c..14661f1262a212f5db0c36e7aa171dfb55800ea4 100644 (file)
--- a/Objects/complexobject.c
+++ b/Objects/complexobject.c
@@ -294,7 +294,7 @@ complex_hash(v)
 {
        double intpart, fractpart;
        int expo;
-       long x;
+       long hipart, x;
        /* This is designed so that Python numbers with the same
           value hash to the same value, otherwise comparisons
           of mapping keys will turn out weird */
@@ -309,7 +309,7 @@ complex_hash(v)
        fractpart = modf(v->cval.real, &intpart);
 #endif
 
-       if (fractpart == 0.0) {
+       if (fractpart == 0.0 && v->cval.imag == 0.0) {
                if (intpart > 0x7fffffffL || -intpart > 0x7fffffffL) {
                        /* Convert to long int and use its hash... */
                        object *w = dnewlongobject(v->cval.real);
@@ -323,8 +323,36 @@ complex_hash(v)
        }
        else {
                fractpart = frexp(fractpart, &expo);
-               fractpart = fractpart*2147483648.0; /* 2**31 */
-               x = (long) (intpart + fractpart) ^ expo; /* Rather arbitrary */
+               fractpart = fractpart * 2147483648.0; /* 2**31 */
+               hipart = (long)fractpart; /* Take the top 32 bits */
+               fractpart = (fractpart - (double)hipart) * 2147483648.0;
+                                               /* Get the next 32 bits */
+               x = hipart + (long)fractpart + (long)intpart + (expo << 15);
+                                               /* Combine everything */
+
+               if (v->cval.imag != 0.0) { /* Hash the imaginary part */
+                       /* XXX Note that this hashes complex(x, y)
+                          to the same value as complex(y, x).
+                          Still better than it used to be :-) */
+#ifdef MPW
+                       {
+                               extended e;
+                               fractpart = modf(v->cval.imag, &e);
+                               intpart = e;
+                       }
+#else
+                       fractpart = modf(v->cval.imag, &intpart);
+#endif
+                       fractpart = frexp(fractpart, &expo);
+                       fractpart = fractpart * 2147483648.0; /* 2**31 */
+                       hipart = (long)fractpart; /* Take the top 32 bits */
+                       fractpart =
+                               (fractpart - (double)hipart) * 2147483648.0;
+                                               /* Get the next 32 bits */
+                       x ^= hipart + (long)fractpart +
+                               (long)intpart + (expo << 15);
+                                               /* Combine everything */
+               }
        }
        if (x == -1)
                x = -2;

diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index f61eaeba58e6905c606e8493f7094144d0223310..1cebf8cecce266678cf5c865de129ae3d95d8cfb 100644 (file)
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -236,9 +236,16 @@ float_hash(v)
                x = (long)intpart;
        }
        else {
+               /* Note -- if you change this code, also change the copy
+                  in complexobject.c */
+               long hipart;
                fractpart = frexp(fractpart, &expo);
-               fractpart = fractpart*2147483648.0; /* 2**31 */
-               x = (long) (intpart + fractpart) ^ expo; /* Rather arbitrary */
+               fractpart = fractpart * 2147483648.0; /* 2**31 */
+               hipart = (long)fractpart; /* Take the top 32 bits */
+               fractpart = (fractpart - (double)hipart) * 2147483648.0;
+                                               /* Get the next 32 bits */
+               x = hipart + (long)fractpart + (long)intpart + (expo << 15);
+                                               /* Combine everything */
        }
        if (x == -1)
                x = -2;