[vtk-developers] Call for Comments: Ascii representation of floats and doubles in files

Thu Mar 29 01:58:55 EDT 2018

VTK's ThirdParty api is different than ITK's . I almost have it
building except when Kits are enabled on windows with shared libs.
I'll ask for help tomorrow.

I did use a similar ITK API for the VTK class

On Wed, Mar 28, 2018 at 8:36 PM, Andras Lasso <lasso at queensu.ca> wrote:
> ITK already uses DoubleConversion library. Could VTK include it the same way?
>
> Andras
>
> -----Original Message-----
> From: vtk-developers <vtk-developers-bounces at vtk.org> On Behalf Of Bill Lorensen
> Sent: Wednesday, March 28, 2018 8:55 PM
> To: Utkarsh Ayachit <utkarsh.ayachit at kitware.com>
> Cc: VTK Developers <vtk-developers at vtk.org>; Will Schroeder <will.schroeder at kitware.com>; David Gobbi <david.gobbi at gmail.com>
> Subject: Re: [vtk-developers] Call for Comments: Ascii representation of floats and doubles in files
>
> I'm having problems on a Windows platform. I'll be asking for help.
>
> The ThirdParty stuff is tricky since not all ThirdParty packages follow the recommended way.
>
> Bill
>
> On Wed, Mar 28, 2018 at 5:19 PM, Utkarsh Ayachit <utkarsh.ayachit at kitware.com> wrote:
>> Funny coincidence, I just got bit but this double-string precision
>> problem in a ParaView issue [1]. Looks forward to having this library
>> in VTK so we can use it. Bill, if you need help with the 3rd party
>> stuff, just holler.
>>
>> Utkarsh
>>
>>
>> [1]
>> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitla
>> b.kitware.com%2Fparaview%2Fparaview%2Fissues%2F18083&data=02%7C01%7Cla
>> sso%40queensu.ca%7Cab25aee0e0ae47e090b608d5950fa5ec%7Cd61ecb3b38b142d5
>> 82c4efb2838b925c%7C1%7C0%7C636578816799629721&sdata=%2F1yBI%2B25wC1xr7
>> Z2agKh1IslyksB6y1k0GUKpfp8PtQ%3D&reserved=0
>>
>> On Wed, Mar 21, 2018 at 8:10 PM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
>>> I'm still working in the MR. It works great but I'm having cmake
>>> issues on Windows. Adding a new third party library is tricky.
>>>
>>> On Mar 21, 2018 2:08 PM, "Isaiah Norton" <isaiah.norton at gmail.com> wrote:
>>>>
>>>> +1. I needed this recently in Slicer, and ended up using ITK's
>>>> +version
>>>> because we link it anyway.
>>>>
>>>>>
>>>>> Not sure if we need to add a new third-party library for this,
>>>>> though, especially one that duplicates so much of C++'s built-in machinery.
>>>>
>>>>
>>>>  Grisu3 (double-conversion) appears to be ~13x faster than the C++
>>>> stream functions (and 6x faster than sprintf):
>>>>
>>>>
>>>> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit
>>>> hub.com%2Fmiloyip%2Fdtoa-benchmark&data=02%7C01%7Classo%40queensu.ca
>>>> %7Cab25aee0e0ae47e090b608d5950fa5ec%7Cd61ecb3b38b142d582c4efb2838b92
>>>> 5c%7C1%7C0%7C636578816799629721&sdata=XjioME1t%2F1TwLSUObFB5GGG9d%2B
>>>> S8f4%2ByVls1%2B5oB1q4%3D&reserved=0
>>>>
>>>> Those numbers are on VS2013/Windows, but that code is easy to build
>>>> locally. The sprintf vs double-conversion conclusion holds on 2015
>>>> macbook with 10.12 SDK. The C++ stream functionality is somewhat closer to sprintf.
>>>>
>>>> [usual benchmark NaCl disclaimer here]
>>>>
>>>> On Thu, Mar 1, 2018 at 11:32 AM, David Gobbi <david.gobbi at gmail.com>
>>>> wrote:
>>>>>
>>>>> I agree that floats should be printed so that conversion is lossless.
>>>>> Python's console output does this and I find it incredibly useful.
>>>>>
>>>>> Not sure if we need to add a new third-party library for this,
>>>>> though, especially one that duplicates so much of C++'s built-in machinery.
>>>>> Isn't it just a matter of printing enough digits?  That's basically
>>>>> what I do in my own code (plus checks for isnan(x) and isinf(x),
>>>>> and a check of the size of fabs(x) for whether to force scientific
>>>>> notation.)
>>>>>
>>>>>  - David
>>>>>
>>>>>
>>>>> On Thu, Mar 1, 2018 at 8:48 AM, Bill Lorensen
>>>>> <bill.lorensen at gmail.com>
>>>>> wrote:
>>>>>>
>>>>>> Will,
>>>>>>
>>>>>> It would go in Common/Core I think. The vtk class would be very small.
>>>>>>
>>>>>> Bill
>>>>>>
>>>>>> On Thu, Mar 1, 2018 at 7:36 AM, Will Schroeder
>>>>>> <will.schroeder at kitware.com> wrote:
>>>>>> > If it works why mess with success? Where would this class
>>>>>> > (vtkNumberToString) be placed, in Common/Core (like vtkIndent)
>>>>>> > or in some IO directory like VTK/IO/Core?
>>>>>> >
>>>>>> > On Thu, Mar 1, 2018 at 10:06 AM, Bill Lorensen
>>>>>> > <bill.lorensen at gmail.com>
>>>>>> > wrote:
>>>>>> >>
>>>>>> >> Folks,
>>>>>> >>
>>>>>> >> I'm working on some examples to save/restore camera, polydata,
>>>>>> >> property, etc. in XML files. The files can be saved as binary
>>>>>> >> or ascii. If I save/restore the info in binary, I get the same
>>>>>> >> values for the saved info. But, to no surprise, when I save the
>>>>>> >> same data in ascii, I don't get the same values. This is
>>>>>> >> because the file writing code does not write enough significant
>>>>>> >> digits.
>>>>>> >>
>>>>>> >> In ITK we solved this problem many years ago. ITK uses a
>>>>>> >> reduced version of the Google double-conversion library,
>>>>>> >> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fgoogle%2Fdouble-conversion&data=02%7C01%7Classo%40queensu.ca%7Cab25aee0e0ae47e090b608d5950fa5ec%7Cd61ecb3b38b142d582c4efb2838b925c%7C1%7C0%7C636578816799629721&sdata=Iaj1ntftOmg4TsPj7U3eaMXoYfiNmT0yqRlQxZvpMC8%3D&reserved=0.
>>>>>> >>
>>>>>> >> We added a small class to ITK that uses the library. The class,
>>>>>> >> itkNumberToString, has a simple API. To convert floating and
>>>>>> >> fixed point numbers to ascii without numerical precision erros,
>>>>>> >>
>>>>>> >> For example, to convert a float, #include "itkNumberToString.h:
>>>>>> >> itk::NumberToString<float> convert; float a = 1.0f/3.0f;
>>>>>> >> std::cout << convert(a) << std::endl;
>>>>>> >>
>>>>>> >> I propose a similar approach in VTK.
>>>>>> >>
>>>>>> >> Comments please,
>>>>>> >>
>>>>>> >> Bill
>>>>>
>>>>>
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