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casting without rounding using coder

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Marc Barnada
Marc Barnada 2022-7-12
评论： Bjorn Gustavsson 2022-7-18
How can I manually trigger casting from a float/double to integer without involving any rounding while using coder?
LUT = single(rand(1,2000)*200);
for i=1:2000
ind = int32(LUT(i));
fprintf("%i\n",ind);
end
When the C++ code is generated it will be similar to:
int ind = static_cast<int>(rt_roundf_snf(LUT[i]));
I am aware that under certain circumstances coder is able to automatically figure out the optimal datatypes for indexing inside for loops resulting then in the desired result:
int ind = static_cast<int>(LUT[i]);

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回答（1 个）

Bjorn Gustavsson
Bjorn Gustavsson 2022-7-12
Well, the only interpretation I can thing of that matches the "casting without rounding" in a sensible way is:
ind = int32(floor(LUT2(i));
That way ind will be the integer part of whatever LUT2 is. But this is still "rounding-off the fractional part".
HTH
  4 个评论
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Marc Barnada
Marc Barnada 2022-7-18
I want to have highly efficient C++ code, and that extra call to rt_roundf_snf has a big impact in the timings of a Look-Up-Table (LUT) function.
Bjorn Gustavsson
Bjorn Gustavsson 2022-7-18
If it is a limited point-of-use and a one-time effort would it be possible to manually edit the generated code?

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