Fix a test to not expect NaNs to be bitwise identical.

Fix a test to not expect NaNs to be bitwise identical.

Different implementations may use different bit-patterns for NaN. e.g. NAN from math.h can be different from 0.0/0.0 (which is used in double.dart)

We should assert that NaNs are bitwise identical in general.

BUG=#26887
R=lrn@google.com

Committed: https://github.com/dart-lang/sdk/commit/2d5e87482c5e680978b7b58b3f2f6450764dd744

[Florian Schneider, 2016-08-12 23:30:31]

Description was changed from

==========
Fix a test to not expect NaNs to be bitwise identical.

BUG=
==========

to

==========
Fix a test to not expect NaNs to be bitwise identical.

Different implementations may use different bit-patterns for NaN. e.g. NAN from
math.h can be different from 0.0/0.0 (which is used in double.dart)

We should assert that NaNs are bitwise identical in general.

BUG=#26887
==========

[Florian Schneider, 2016-08-12 23:30:31]

fschneider@google.com changed reviewers:
+ lrn@google.com

[Lasse Reichstein Nielsen, 2016-08-12 23:52:38]

https://codereview.chromium.org/2247553002/diff/1/tests/lib/math/double_pow_t...
File tests/lib/math/double_pow_test.dart (right):

https://codereview.chromium.org/2247553002/diff/1/tests/lib/math/double_pow_t...
tests/lib/math/double_pow_test.dart:121: Expect.equals(pow(0.0, d), pow(-0.0,
d));
I'm not sure that's what we want.

If the problem is with different payload NaNs not being identical, then they are
probably not equal either (since NaN isn't even equal to itself).

According to https://api.dartlang.org/stable/1.18.1/dart-math/pow.html, we only
get NaN for a NaN input or pow(finite-negative, non-integer) so these tests
shouldn't be affected at all.

https://codereview.chromium.org/2247553002/diff/1/tests/lib/math/double_pow_t...
tests/lib/math/double_pow_test.dart:139: Expect.equals(1/pow(d, Infinity),
pow(d, -Infinity));
Again, this should hold, and if it doesn't because of different payload NaNs,
equals shouldn't work either.

[Florian Schneider, 2016-08-13 00:01:30]

https://codereview.chromium.org/2247553002/diff/1/tests/lib/math/double_pow_t...
File tests/lib/math/double_pow_test.dart (right):

https://codereview.chromium.org/2247553002/diff/1/tests/lib/math/double_pow_t...
tests/lib/math/double_pow_test.dart:121: Expect.equals(pow(0.0, d), pow(-0.0,
d));
On 2016/08/12 23:52:38, Lasse Reichstein Nielsen wrote:
> I'm not sure that's what we want.
> 
> If the problem is with different payload NaNs not being identical, then they
are
> probably not equal either (since NaN isn't even equal to itself).
> 
> According to https://api.dartlang.org/stable/1.18.1/dart-math/pow.html, we
only
> get NaN for a NaN input or pow(finite-negative, non-integer) so these tests
> shouldn't be affected at all.

Never mind my first attempt: Can't use == on NaN in any case.

I can only check that both sides are NaN or not, but I don't want to rely on a
specific bit pattern.

[Lasse Reichstein Nielsen, 2016-08-13 12:14:59]

That looks correct. LGTM.

I'm still a little sad that we actually generate different NaNs. We shouldn't be
generating a payload out of nothing, so I'm guessing it's mainly the sign that
differs (because -d doesn't check for NaN), and we have lived with that so far.

[Florian Schneider, 2016-08-16 22:57:50]

Description was changed from

==========
Fix a test to not expect NaNs to be bitwise identical.

Different implementations may use different bit-patterns for NaN. e.g. NAN from
math.h can be different from 0.0/0.0 (which is used in double.dart)

We should assert that NaNs are bitwise identical in general.

BUG=#26887
==========

to

==========
Fix a test to not expect NaNs to be bitwise identical.

Different implementations may use different bit-patterns for NaN. e.g. NAN from
math.h can be different from 0.0/0.0 (which is used in double.dart)

We should assert that NaNs are bitwise identical in general.

BUG=#26887
R=lrn@google.com

Committed:
https://github.com/dart-lang/sdk/commit/2d5e87482c5e680978b7b58b3f2f6450764dd744
==========

[Florian Schneider, 2016-08-16 22:57:51]

Committed patchset #2 (id:20001) manually as
2d5e87482c5e680978b7b58b3f2f6450764dd744 (presubmit successful).