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PERF: (partial) fix for np_datetime.c performance regression #57988

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PERF: (partial) fix for np_datetime.c performance regression #57988

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aecba4b
faster ifrac
dontgoto Mar 24, 2024
6f43de0
remove unnecessary statement
dontgoto Mar 24, 2024
47a0d9b
shorten <s assignment
dontgoto Mar 24, 2024
61c5cae
remove assignments
dontgoto Mar 24, 2024
e4c64b2
shorten frac assignments
dontgoto Mar 24, 2024
fa3ff63
shorten days logic
dontgoto Mar 24, 2024
9d768d6
remove unnecessary assignments
dontgoto Mar 24, 2024
c9f75b1
reuse td
dontgoto Mar 24, 2024
aba6c3a
fix regression for td close to int64 bounds
dontgoto Mar 25, 2024
e7c02e8
re-add unnecessary conversions
dontgoto Mar 25, 2024
6b464a5
Merge branch 'main' into 240324_57951_potential_regression_induced_by_re
dontgoto Mar 25, 2024
b3c0199
remove sign if
dontgoto Mar 25, 2024
5a04d8d
remove mod seconds if layer
dontgoto Mar 25, 2024
39c77ab
remove second negative check if layer
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2227b1b
duplicate larger than day check
dontgoto Mar 25, 2024
0171a7c
remove forgetten functions
dontgoto Mar 25, 2024
1492bc9
make days assignment conditions explicit
dontgoto Mar 25, 2024
2e670c0
directly flip out.days
dontgoto Mar 25, 2024
0316442
extract normalization to secs
dontgoto Mar 25, 2024
b61b71c
reintroduce sfrac, minimize casting
dontgoto Mar 25, 2024
c3b19e0
add comment
dontgoto Mar 26, 2024
80ce283
fix error
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c9a1efd
Merge remote-tracking branch 'origin/240324_57951_potential_regressio…
dontgoto Mar 26, 2024
322252e
remove uneven_in_seconds
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reintroduce sfrac, minimize casting
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@dontgoto
dontgoto committed Mar 25, 2024
commit b61b71c8e230ff56b1daa089189588ef70c0bcb4
58 changes: 27 additions & 31 deletions pandas/_libs/src/vendored/numpy/datetime/np_datetime.c
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Original file line number Diff line number Diff line change
Expand Up @@ -752,59 +752,55 @@ void pandas_timedelta_to_timedeltastruct(npy_timedelta td,
}

const npy_int64 per_day = sec_per_day * per_sec;
npy_int64 ifrac = td;
const int sign = td < 0 ? -1 : 1;
const int is_negative = td < 0 ? 1 : 0;
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@WillAyd WillAyd Mar 26, 2024

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You can use bool here - our minimum supported standard is C11
const int uneven_in_seconds = td % per_sec != 0 ? 1 : 0;
// put frac in seconds
td = td / per_sec;
npy_int64 sfrac = td / per_sec - is_negative * uneven_in_seconds;
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@WillAyd WillAyd Mar 26, 2024

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Am I reading this right that it just can add/subtract 1 when uneven_in_seconds is true? I might be missing the point but that feels a bit off - not sure we have full test coverage in all precisions
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@dontgoto dontgoto Mar 26, 2024

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Thanks for scratching your head at this. It's a leftover from a different optimisation route that was not successful in the end. I moved the subtraction into the if body again (same as in the main version) so it should be clearer now. Also now the speedup is at where I had it with the previous version that did not pass the tests.
if (sign < 0) {
td -= uneven_in_seconds;
// even fraction
if ((-td % sec_per_day) != 0) {
// days = td / sec_per_day - is_even_fraction
out->days = td / sec_per_day - 1;
td -= sec_per_day * out->days;
if ((-sfrac % sec_per_day) != 0) {
out->days = sfrac / sec_per_day - 1;
sfrac -= sec_per_day * out->days;
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@WillAyd WillAyd Mar 26, 2024

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Is this exactly the same as before? Previously it looks like out->days would be positive but this is now negative?

Sorry if misreading - again just want to be careful as I'm not sure how well our test cases are hitting all of these branches
} else {
if (td <= sec_per_day) {
out->days = td / sec_per_day;
td = -td;
td += out->days * sec_per_day;
} else {
td = -td;
if (sfrac <= sec_per_day) {
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@WillAyd WillAyd Mar 26, 2024

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This seems to add more branching than what we had before, so I'm a little hesitant to say this is faster overall even though it may show up in some of our benchmarks. What kind of difference are you seeing in the current state?
out->days = sfrac / sec_per_day;
sfrac -= out->days * sec_per_day;
}
sfrac = -sfrac;
}
} else if (td >= sec_per_day) {
out->days = td / sec_per_day;
td -= out->days * sec_per_day;
} else if (sfrac >= sec_per_day) {
out->days = sfrac / sec_per_day;
sfrac -= out->days * sec_per_day;
}

if (td >= sec_per_hour) {
out->hrs = (npy_int32)(td / sec_per_hour);
td %= sec_per_hour;
if (sfrac >= sec_per_hour) {
out->hrs = (npy_int32)(sfrac / sec_per_hour);
sfrac %= sec_per_hour;
}

if (td >= sec_per_min) {
out->min = (npy_int32)(td / sec_per_min);
td %= sec_per_min;
if (sfrac >= sec_per_min) {
out->min = (npy_int32)(sfrac / sec_per_min);
sfrac %= sec_per_min;
}

if (td >= 0) {
out->sec = (npy_int32)td;
if (sfrac >= 0) {
out->sec = (npy_int32)sfrac;
}

if (base > NPY_FR_s) {
ifrac = (ifrac - out->days * per_day) % per_sec;
npy_int32 ifrac = (npy_int32)((td - out->days * per_day) % per_sec);

if (base == NPY_FR_ms) {
out->ms = (npy_int32)ifrac;
out->ms = ifrac;
} else if (base == NPY_FR_us) {
out->ms = (npy_int32)(ifrac / 1000LL);
out->us = (npy_int32)(ifrac % 1000LL);
out->ms = ifrac / 1000LL;
out->us = ifrac % 1000LL;
} else if (base == NPY_FR_ns) {
out->ms = (npy_int32)(ifrac / (1000LL * 1000LL));
out->ms = ifrac / (1000LL * 1000LL);
ifrac = ifrac % (1000LL * 1000LL);
out->us = (npy_int32)(ifrac / 1000LL);
out->nanoseconds = (npy_int32)(ifrac % 1000LL);
out->us = ifrac / 1000LL;
out->nanoseconds = ifrac % 1000LL;
}
out->microseconds = out->ms * 1000 + out->us;
}
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