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This patch addresses two main issues: (1) There exist some non-fatal

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errors in some of the hash algorithms. For exmaple, in float_hash and
complex_hash a certain part of the value is not included in the hash
calculation. See Tim's, Guido's, and my discussion of this on
python-dev in May under the title "fix float_hash and complex_hash for
64-bit *nix"

(2) The hash algorithms that use pointers (e.g. func_hash, code_hash)
are universally not correct on Win64 (they assume that sizeof(long) ==
sizeof(void*))

As well, this patch significantly cleans up the hash code. It adds the
two function _Py_HashDouble and _PyHash_VoidPtr that the various
hashing routine are changed to use.

These help maintain the hash function invariant: (a==b) =>
(hash(a)==hash(b))) I have added Lib/test/test_hash.py and
Lib/test/output/test_hash to test this for some cases.
This commit is contained in:
Fred Drake 2000-06-29 19:17:04 +00:00
parent b46696c0ed
commit 13634cf7a4
10 changed files with 126 additions and 49 deletions
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37
Objects/complexobject.c
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@ -285,8 +285,7 @@ complex_hash(v)
PyComplexObject *v;
{
double intpart, fractpart;
int expo;
long hipart, x;
long 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 */
@ -302,7 +301,7 @@ complex_hash(v)
#endif
if (fractpart == 0.0 && v->cval.imag == 0.0) {
if (intpart > 0x7fffffffL || -intpart > 0x7fffffffL) {
if (intpart > LONG_MAX || -intpart > LONG_MAX) {
/* Convert to long int and use its hash... */
PyObject *w = PyLong_FromDouble(v->cval.real);
if (w == NULL)
@ -314,36 +313,18 @@ complex_hash(v)
x = (long)intpart;
}
else {
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 */
x = _Py_HashDouble(v->cval.real);
if (x == -1)
return -1;
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 */
long y = _Py_HashDouble(v->cval.imag);
if (y == -1)
return -1;
x += y;
}
}
if (x == -1)