I_love_Saundarya's blog

Can FFT be applied if the coefficients are double/floating point numbers ??
By I_love_Saundarya, history, 6 years ago, In English

Say, I have 2 vectors : — (1,2,3) and (0.3,0.5,1) .

Can FFT be applied to find the multiplication of these 2 polynomials ?

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6 years ago, # |
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Yes.

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    9 months ago, # ^ |
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    How?

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      9 months ago, # ^ |
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      Why did you think that FFT is only applicable to integers? Normal FFT uses floating point numbers in their calculations and the result returned is their floating point convolution. It's worked with as integers for multiplying polynomials with integer coefficients.

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        9 months ago, # ^ |
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        I can't do it because i do round in my fft, i have to multiplay the polynomial with a 10^number to make it integer.

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          9 months ago, # ^ |
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          I don't understand what you are talking about. FFT is suitable for complex/floating point convolution, there's no need to multiply by some power of 10 to pass integers to FFT.

          maybe you think that FFT is NTT?

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            9 months ago, # ^ |
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            I bass doubles ok but i meant can i multiplay 2.5+3.2*a^1+4.5*a^2 With 3.5+1.3*a^1+3.4*a^2 ? or can i multplay two doubles as a bigdoubles with fft like bigint with fft like this 9493888383893383883.429382828484828482883 without shifting the dot ?

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              9 months ago, # ^ |
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              Explain it more clearly.

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                9 months ago, # ^ |
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                Ok I want to devide two polynomials, how can i do it?

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              9 months ago, # ^ |
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              Why wouldn't you like to shift the dot? Also for big floating point numbers: the mantissa can be FFTed.

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                9 months ago, # ^ |
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                Beacause my real problem is to divide 2 bigints. How can i do long division?

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