[erlang-patches] new float_to_list/2

Fredrik fredrik@REDACTED
Fri Jan 11 15:29:55 CET 2013 

Thanks,
It's building in 'master-pu' now!

BR Fredrik Gustafsson
Erlang OTP Team
On 01/11/2013 03:11 PM, Serge Aleynikov wrote:
> Ok. Here's the patch rebased to master:
>
> git fetch https://github.com/saleyn/otp/tree/float_to_list_2
>
> https://github.com/saleyn/otp/compare/master...float_to_list_2
> https://github.com/saleyn/otp/compare/master...float_to_list_2.patch
>
> Regards,
>
> Serge
>
> On 1/11/2013 8:53 AM, Björn-Egil Dahlberg wrote:
>> On 2013-01-11 14:24, Serge Aleynikov wrote:
>>> While looking at this I see that the code in folder
>>> "erts/emulator/sys/vxworks" is present in maint but missing in the
>>> master branch.  Is this intentional?  If so, should I remove the part of
>>> the patch designed for vxworks?
>> Yes. Any and all vxworks support has been removed in R16 from OTP except
>> for epmd, erl_interface and ic.
>>
>> // Björn-Egil
>>> On 1/11/2013 3:52 AM, Fredrik wrote:
>>>> Hey,
>>>> Could you please rebase this on current 'master' branch?
>>>>
>>>> BR Fredrik Gustafsson
>>>> Erlang OTP Team
>>>> On 01/11/2013 04:06 AM, Serge Aleynikov wrote:
>>>>> I implemented Lukas's recommendations that were presenting an
>>>>> acceptance
>>>>> issue of the new function, so the current version of the patch does:
>>>>>
>>>>> 1. float_to_list/1 is backwards compatible.
>>>>> 2. float_to_list(X,[]) gives the same result as float_to_list(X).
>>>>> 3. float_to_list(X,[{decimals,N}]) uses the new fast implementation
>>>>> (with the optional compact option).
>>>>> 4. float_to_list(X,[{scientific,M}]) gives the same result as
>>>>> float_to_list(X) with the ability to control the number of decimals.
>>>>>
>>>>> The only item from Lucas's list that I left unchanged was the
>>>>> modification to erts/lib_src/common/erl_printf_format.c to take
>>>>> advantage of the speed improvement of the new implementation.  I am
>>>>> including a patch in this email that implements this logic, but I
>>>>> decided to leave the integration task to the OTP team since
>>>>> erl_printf_format.c is actually compiled into a liberts_internal.a
>>>>> library and I didn't want to introduce a dependency of it on other code
>>>>> - this should be decided by maintainers.
>>>>>
>>>>> The test cases of float_to_list/{1,2} have been updated.
>>>>>
>>>>> git fetch https://github.com/saleyn/otp/tree/float_to_list_2
>>>>>
>>>>> https://github.com/saleyn/otp/compare/maint...float_to_list_2
>>>>> https://github.com/saleyn/otp/compare/maint...float_to_list_2.patch
>>>>>
>>>>> Regards,
>>>>>
>>>>> Serge
>>>>>
>>>>> On 8/23/2012 5:10 AM, Lukas Larsson wrote:
>>>>>> Hi,
>>>>>>
>>>>>> I'll put it in the backlog and we'll see if it gets prioritized for
>>>>>> R16B.
>>>>>>
>>>>>> As always if you (or someone else) wants make sure it gets in, the
>>>>>> best
>>>>>> way to ensure that is to send an updated patch.
>>>>>>
>>>>>> Lukas
>>>>>>
>>>>>>
>>>>>> On 22/08/12 21:17, Serge Aleynikov wrote:
>>>>>>> I am certainly very happy to hear that you finally agreed to include
>>>>>>> this in the distribution.  The changes proposed below seem reasonable
>>>>>>> and simple.  Will the OTP team be able to modify my patch to
>>>>>>> implement
>>>>>>> them?
>>>>>>>
>>>>>>> On 8/22/2012 12:01 PM, Lukas Larsson wrote:
>>>>>>>> Hello Serge!
>>>>>>>>
>>>>>>>> I think we have finally agreed how we want this functionality to
>>>>>>>> work.
>>>>>>>>
>>>>>>>> float_to_list/1 should be left as it is now for backwards
>>>>>>>> compatibility.
>>>>>>>> float_to_list(1.0,[]) should give the same as float_to_list(1.0).
>>>>>>>> float_to_list(1.0,[{decimals,X}]) should use your faster
>>>>>>>> implementation
>>>>>>>> (with the optional compact option).
>>>>>>>> float_to_list(1.0,[{scientific,Y}]) should give the same as
>>>>>>>> float_to_list(1.0) if Y is 20.
>>>>>>>>
>>>>>>>> We would also like the string rendering part of
>>>>>>>> sys_double_to_chars_fast
>>>>>>>> to be put into
>>>>>>>> erts/lib_src/common/erl_printf_format.c:fmt_double. This
>>>>>>>> way other parts of the vm which print floats will benefit from your
>>>>>>>> changes!
>>>>>>>>
>>>>>>>> I hope our indecisiveness have not caused you to shy away from
>>>>>>>> taking
>>>>>>>> this feature into Erlang/OTP. If you have any further questions or
>>>>>>>> ponderings just let me know.
>>>>>>>>
>>>>>>>> Lukas
>>>>>>>>
>>>>>>>> On 18/07/12 20:47, Serge Aleynikov wrote:
>>>>>>>>> On 7/18/2012 5:18 AM, Lukas Larsson wrote:
>>>>>>>>>> However, I would also like the fast functionality to be used by
>>>>>>>>>> float_to_list_1 as well, is possible to do this and stay backwards
>>>>>>>>>> compatible? Hopefully you just have to shift the comma and add
>>>>>>>>>> e+XX at
>>>>>>>>>> the end of the optimized case and call sys_double_to_chars for the
>>>>>>>>>> unoptimized.
>>>>>>>>> See my comments below regarding 'scientific' option.  Since
>>>>>>>>> float_to_list_2 is a new function I would think that you are
>>>>>>>>> questioning
>>>>>>>>> the issue of backward compatibility only in terms of converting
>>>>>>>>> float_to_list_1 to use float_to_list_2 implementation.  However, I
>>>>>>>>> think
>>>>>>>>> that this will have adverse performance tax on float_to_list_2,
>>>>>>>>> which
>>>>>>>>> will diminish the benefit.  It's been a while however, since I
>>>>>>>>> wrote
>>>>>>>>> that patch, perhaps there's a way to retrofit scientific notation
>>>>>>>>> without a performance penalty.
>>>>>>>>>
>>>>>>>>> It's more than simple shifting of the comma, since there's also
>>>>>>>>> rounding
>>>>>>>>> involved.
>>>>>>>>>
>>>>>>>>> This case is easy:
>>>>>>>>>
>>>>>>>>> 4>  float_to_list(1.01234).
>>>>>>>>> "1.01234000000000001762e+00"
>>>>>>>>> 5>  float_to_list(1.01234, [{decimals, 20}]).
>>>>>>>>> "1.01234000000000001762"
>>>>>>>>>
>>>>>>>>> This case is a bit more complex (illustration of rounding impact):
>>>>>>>>>
>>>>>>>>> 7>  float_to_list(10123412345.0123451234).
>>>>>>>>> "1.01234123450123443604e+10"
>>>>>>>>> 8>  float_to_list(10123412345.0123451234, [{decimals, 20}]).
>>>>>>>>> "10123412345.01234436035156250000"
>>>>>>>>>
>>>>>>>>>> Also float_to_list(1.0) should return the same thing as
>>>>>>>>>> float_to_list(1.0,[]), otherwise the API will be inconsistent
>>>>>>>>>> with how
>>>>>>>>>> other such APIs work.
>>>>>>>>> Actually if you trace this subject back there was another
>>>>>>>>> request that
>>>>>>>>> the default number of decimals is chosen to be consistent with what
>>>>>>>>> printf() does, so I changed the implementation to accommodate that
>>>>>>>>> request:
>>>>>>>>>
>>>>>>>>> Eshell V5.9  (abort with ^G)
>>>>>>>>> 1>  float_to_list(1.0, []).
>>>>>>>>> "1.000000"
>>>>>>>>>
>>>>>>>>> Which is different from the default of float_to_list/1:
>>>>>>>>>
>>>>>>>>> 2>  float_to_list(1.0).
>>>>>>>>> "1.00000000000000000000e+00"
>>>>>>>>>
>>>>>>>>> Maybe one could introduce a 'scientific' option to
>>>>>>>>> float_to_list/2, to
>>>>>>>>> use the float_to_list/1 implementation?
>>>>>>>>>
>>>>>>>>> Serge
>>>>>>>>>
>>>>>>>>>> On 24/05/12 16:02, Serge Aleynikov wrote:
>>>>>>>>>>> Henrik,
>>>>>>>>>>>
>>>>>>>>>>> Fetch:    git fetch
>>>>>>>>>>> https://github.com/saleyn/otp/tree/float_to_list_2
>>>>>>>>>>> Diff:    https://github.com/saleyn/otp/compare/float_to_list_2
>>>>>>>>>>>
>>>>>>>>>>> I added the definition for the new BIF to make the type checker
>>>>>>>>>>> happy:
>>>>>>>>>>> https://github.com/saleyn/otp/commit/f9ddbeda5426ca83cda03c06a9860220ea4a22c7
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Once you do the "otp_build tests", how do you execute all tests
>>>>>>>>>>> suites
>>>>>>>>>>> in $ERL_TOP or if possible only tests in a given SUITE?  I
>>>>>>>>>>> tried the
>>>>>>>>>>> following but all tests fail:
>>>>>>>>>>>
>>>>>>>>>>> [otp/erts/emulator/test]$ ../../../bin/erl -noshell -s
>>>>>>>>>>> test_server_ctrl
>>>>>>>>>>> run_test DIR "." -s erlang halt
>>>>>>>>>>>
>>>>>>>>>>> I did however run individual tests in bif_SUIT:types to make
>>>>>>>>>>> sure my
>>>>>>>>>>> patch didn't break anything.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Serge
>>>>>>>>>>>
>>>>>>>>>>> On 5/24/2012 5:17 AM, Henrik Nord wrote:
>>>>>>>>>>>> Hi again.
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> This test is not passing: emulator/bif_SUIT:types
>>>>>>>>>>>>
>>>>>>>>>>>> No type information:
>>>>>>>>>>>>
>>>>>>>>>>>> [{erlang,float_to_list,2}]
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> On 04/21/2012 07:19 AM, Serge Aleynikov wrote:
>>>>>>>>>>>>> git fetch https://github.com/saleyn/otp/tree/float_to_list_2
>>>>>>>>>>> _______________________________________________
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