[erlang-patches] new float_to_list/2

Serge Aleynikov <>
Fri Jan 11 16:55:53 CET 2013


Sorry the test case line was the "last moment" add on.  It is fixed now
in my branch below.

On 1/11/2013 10:44 AM, Fredrik wrote:
> Hey,
> Your patch does not build:
> "
> 
> emulator_test ../emulator_test/num_bif_SUITE.erl:130: illegal pattern
> "
> 
> 
> Please have a look at it, and give me notice when you are done.
> 
> 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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