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Issue #23517: fromtimestamp() and utcfromtimestamp() methods of

Browse source 
datetime.datetime now round microseconds to nearest with ties going to nearest
even integer (ROUND_HALF_EVEN), as round(float), instead of rounding towards
-Infinity (ROUND_FLOOR).

pytime API: replace _PyTime_ROUND_HALF_UP with _PyTime_ROUND_HALF_EVEN. Fix
also _PyTime_Divide() for negative numbers.

_PyTime_AsTimeval_impl() now reuses _PyTime_Divide() instead of reimplementing
rounding modes.
This commit is contained in:
Victor Stinner 2015-09-09 01:02:23 +02:00
parent 69cc487df4
commit 7667f58151
8 changed files with 148 additions and 185 deletions
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71
Python/pytime.c
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@ -61,18 +61,15 @@ _PyLong_FromTime_t(time_t t)
}
double
_PyTime_RoundHalfUp(double x)
_PyTime_RoundHalfEven(double x)
{
/* volatile avoids optimization changing how numbers are rounded */
volatile double d = x;
if (d >= 0.0)
d = floor(d + 0.5);
else
d = ceil(d - 0.5);
return d;
double rounded = round(x);
if (fabs(x-rounded) == 0.5)
/* halfway case: round to even */
rounded = 2.0*round(x/2.0);
return rounded;
}
static int
_PyTime_DoubleToDenominator(double d, time_t *sec, long *numerator,
double denominator, _PyTime_round_t round)
@ -84,8 +81,8 @@ _PyTime_DoubleToDenominator(double d, time_t *sec, long *numerator,
floatpart = modf(d, &intpart);
floatpart *= denominator;
if (round == _PyTime_ROUND_HALF_UP)
floatpart = _PyTime_RoundHalfUp(floatpart);
if (round == _PyTime_ROUND_HALF_EVEN)
floatpart = _PyTime_RoundHalfEven(floatpart);
else if (round == _PyTime_ROUND_CEILING)
floatpart = ceil(floatpart);
else
@ -140,8 +137,8 @@ _PyTime_ObjectToTime_t(PyObject *obj, time_t *sec, _PyTime_round_t round)
volatile double d;
d = PyFloat_AsDouble(obj);
if (round == _PyTime_ROUND_HALF_UP)
d = _PyTime_RoundHalfUp(d);
if (round == _PyTime_ROUND_HALF_EVEN)
d = _PyTime_RoundHalfEven(d);
else if (round == _PyTime_ROUND_CEILING)
d = ceil(d);
else
@ -266,8 +263,8 @@ _PyTime_FromFloatObject(_PyTime_t *t, double value, _PyTime_round_t round,
d = value;
d *= to_nanoseconds;
if (round == _PyTime_ROUND_HALF_UP)
d = _PyTime_RoundHalfUp(d);
if (round == _PyTime_ROUND_HALF_EVEN)
d = _PyTime_RoundHalfEven(d);
else if (round == _PyTime_ROUND_CEILING)
d = ceil(d);
else
@ -351,14 +348,16 @@ _PyTime_AsNanosecondsObject(_PyTime_t t)
}
static _PyTime_t
_PyTime_Divide(_PyTime_t t, _PyTime_t k, _PyTime_round_t round)
_PyTime_Divide(const _PyTime_t t, const _PyTime_t k,
const _PyTime_round_t round)
{
assert(k > 1);
if (round == _PyTime_ROUND_HALF_UP) {
_PyTime_t x, r;
if (round == _PyTime_ROUND_HALF_EVEN) {
_PyTime_t x, r, abs_r;
x = t / k;
r = t % k;
if (Py_ABS(r) >= k / 2) {
abs_r = Py_ABS(r);
if (abs_r > k / 2 || (abs_r == k / 2 && (Py_ABS(x) & 1))) {
if (t >= 0)
x++;
else
@ -369,11 +368,15 @@ _PyTime_Divide(_PyTime_t t, _PyTime_t k, _PyTime_round_t round)
else if (round == _PyTime_ROUND_CEILING) {
if (t >= 0)
return (t + k - 1) / k;
else
return t / k;
}
else {
if (t >= 0)
return t / k;
else
return (t - (k - 1)) / k;
}
else
return t / k;
}
_PyTime_t
@ -392,17 +395,12 @@ static int
_PyTime_AsTimeval_impl(_PyTime_t t, struct timeval *tv, _PyTime_round_t round,
int raise)
{
const long k = US_TO_NS;
_PyTime_t secs, ns;
int res = 0;
int usec;
secs = t / SEC_TO_NS;
ns = t % SEC_TO_NS;
if (ns < 0) {
ns += SEC_TO_NS;
secs -= 1;
}
#ifdef MS_WINDOWS
/* On Windows, timeval.tv_sec is a long (32 bit),
@ -427,23 +425,12 @@ _PyTime_AsTimeval_impl(_PyTime_t t, struct timeval *tv, _PyTime_round_t round,
res = -1;
#endif
if (round == _PyTime_ROUND_HALF_UP) {
_PyTime_t r;
usec = (int)(ns / k);
r = ns % k;
if (Py_ABS(r) >= k / 2) {
if (ns >= 0)
usec++;
else
usec--;
}
usec = (int)_PyTime_Divide(ns, US_TO_NS, round);
if (usec < 0) {
usec += SEC_TO_US;
tv->tv_sec -= 1;
}
else if (round == _PyTime_ROUND_CEILING)
usec = (int)((ns + k - 1) / k);
else
usec = (int)(ns / k);
if (usec >= SEC_TO_US) {
else if (usec >= SEC_TO_US) {
usec -= SEC_TO_US;
tv->tv_sec += 1;
}