[Insight-developers] Trying to make a Single Precision ITK, any suggestions on type weirdness?

[Williams, Norman K]

Update: Spent some more time beating on this with GCC 4.4.8 and ICC, and
got it down to 5 compiler errors, all having to do with the compiler
somehow confusing itk::Point with vnl_vector and matrix types.
No idea how this didn't happen before.
--
Kent Williams norman-k-williams at uiowa.edu






On 10/25/13 4:19 PM, "Williams, Norman K" <norman-k-williams at uiowa.edu>
wrote:

>This is a project Hans put me on this morning.  Basically trying to get
>ITK to where all (or almost all) its internal computation happens in
>single precision. There are several issues with actually unleashing this
>on the world, but for now I'm just trying to get ITK to build, so I can
>start testing.
>
>The core change is to make the Point, Spacing and Direction Types in
>itk::ImageBase use float instead of double.
>
>Just making this one change did cause a bunch of compiler errors, but once
>I solved the knotty problem of itkImageTransformHelper, it was mostly
>pretty trivial, obvious changes.
>
>Until I got down to this: multiplying a matrix by a vnlVector blows both
>GCC and ICC's minds, in a way I don't understand.  It boils down to this
>code:
>
>typedef vnl_vector_fixed<float,3>    vnlVectorType;
>typedef itk::Matrix<NumericType,3,3> MatrixType;
>
>MatrixType    matrix;
>vnlVectorType v2;
>vnlVectorType resultVnlVector = matrix * v2;
>
>For which Intel ICC gives this error:
>[ 57%] Building CXX object
>Modules/Core/Common/test/CMakeFiles/ITKCommon2TestDriver.dir/itkMatrixTest
>.
>cxx.o
>ITKv4/Modules/Core/Common/test/itkMatrixTest.cxx(68): error: more than one
>operator "*" matches these operands:
>            function "itk::Matrix<T, NRows, NColumns>::operator*(const
>itk::Point<T, NColumns> &) const [with T=float, NRows=3U, NColumns=3U]"
>            function "itk::Matrix<T, NRows, NColumns>::operator*(const
>vnl_vector<T> &) const [with T=float, NRows=3U, NColumns=3U]"
>            operand types are: MatrixType * vnlVectorType
>
>GCC 4.4.8 gives basically the same error.
>
>This makes no sense to me. It suggests that the compiler thinks the
>argument, const vnl_vector_fixed<float,3> &, is close enough in type to
>const itk::Point<float,3> & that it can't decide which version of
>operator* to use.
>
>
>Anyone have any suggestions on how to fix this?  The weirdest part is that
>this test doesn't have anything to do with the change to itk::ImageBase.
>I made some minor changes to itk::Point to allow for more flexible
>initialization, but I did not make it type-compatible with
>vnl_vector_fixed!
>
>My current work is here:
>
>https://github.com/BRAINSia/ITK/tree/SinglePrecisionImageParams
>
>Thanks in advance for any help you can offer!
>--
>Kent Williams norman-k-williams at uiowa.edu
>
>
>
>
>
>
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