floating point / real number

Moderator (Company: Titel) #3041233
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Up to now real numbers aren't synthesizable "automatically". You 
cannot write:
1
signal r, a, b, c, x, y, z : real;
2

3
  c <= a-b+3.3;
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  z <= x+y;
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  r <= c*z;
Instead you must implement the datapath by using IP-Cores or coding by 
yourself.

But:
WHAT is your actual problem?
WHY do you need floats?
#3041912
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Do you realy nead "floating point" or does fixpoint fits to your 
project?

So you could consider your integer variables as fixpoint values e.g. a 
8bit integer as a fixpoint with 4 integer and 4 fractional digits:
  deciaml    binary
     0.06125 0000_0001
     0.125   0000_0010
     0.5     0000_1000
     1.0     0001_0000
     3.75    0011_1100
OP (Company: student) #3042513
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i am working on implementation of neural networks on FPGA. which 
requires addition and multiplication of real numbers.
i am and Electronics and communication student. i dont know what is IP 
core.
My professors have told me that i should define the package for using 
real numbers.
Guest #3065200
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... do you know what is a real number ? look for IEEE754 for example
... what range/precision do you need ? how big/small accurate should 
they be ?  (maybe fixed point is the way to go).

look at opencores.org, there are some fpu implementations there...
Guest #3065234
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I think in case of an FPGA-implementation of a neural network (mlp?) you 
will have a big amount of parallel mult operations, which means a lot of 
ressource-requirement especially in case of float values. First you 
should check if you really need fp-precision.

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