Exponential code in VHDL

Zaid Al-Hilli
Guest

Wed Jul 27, 2011 11:19 am

Hi all,

I am about implementing a VHDL code but I am facing problem, I have an
exponential operation and I want to run that code op an FPGA board!!

Generally speaking the assignment is: X = (1 / (1+ exp((y + 87. Cool

/
8.5)));

Would you please help me in that?

Many thanks in advance...

Zaid

Rob Gaddi
Guest

Wed Jul 27, 2011 4:09 pm

On 7/27/2011 2:19 AM, Zaid Al-Hilli wrote:

Quote:

Hi all,

I am about implementing a VHDL code but I am facing problem, I have an
exponential operation and I want to run that code op an FPGA board!!

Generally speaking the assignment is: X = (1 / (1+ exp((y + 87. Cool

/
8.5)));

Would you please help me in that?

Many thanks in advance...

Zaid

Yeah, bound the range of y sufficiently that you can implement the
entire thing in a RAM lookup table.

--
Rob Gaddi, Highland Technology
Email address is currently out of order

Benjamin Couillard
Guest

Wed Jul 27, 2011 7:23 pm

On 27 juil, 05:19, Zaid Al-Hilli <z.alhil...@gmail.com> wrote:

Quote:

Hi all,

I am about implementing a VHDL code but I am facing problem, I have an
exponential operation and I want to run that code op an FPGA board!!

Generally speaking the assignment is: X = (1 / (1+ exp((y + 87. Cool

/
8.5)));

Would you please help me in that?

Many thanks in advance...

Zaid

One simple way would be to use a look-up table implemented in a ROM.
With "y" being the address and X being the data read at "y" address.
This solution would work well if the range of "y" in bits is smaller
or equal to 16 bits. If "y" is 32-bit wide then I don't think a look-
up table implemented in a FPGA-Rom will work.

noobie
Guest

Thu Jul 28, 2011 9:31 am

On Jul 27, 2:19 pm, Zaid Al-Hilli <z.alhil...@gmail.com> wrote:

Quote:

Hi all,

I am about implementing a VHDL code but I am facing problem, I have an
exponential operation and I want to run that code op an FPGA board!!

Generally speaking the assignment is: X = (1 / (1+ exp((y + 87. Cool

/
8.5)));

Would you please help me in that?

Many thanks in advance...

Zaid

Use Taylor series expansion for the calculation of this equation. Use
fixed point arithmetic.

Zaid Al-Hilli
Guest

Fri Jul 29, 2011 12:41 pm

On Jul 27, 7:23 pm, Benjamin Couillard <benjamin.couill...@gmail.com>
wrote:

Quote:

On 27 juil, 05:19, Zaid Al-Hilli <z.alhil...@gmail.com> wrote:

Hi all,

I am about implementing a VHDL code but I am facing problem, I have an
exponential operation and I want to run that code op an FPGA board!!

Generally speaking the assignment is: X = (1 / (1+ exp((y + 87. Cool

/
8.5)));

Would you please help me in that?

Many thanks in advance...

Zaid

One simple way would be to use a look-up table implemented in a ROM.
With "y" being the address and X being the data read at "y" address.
This solution would work well if the range of "y" in bits is smaller
or equal to 16 bits. If "y" is 32-bit wide then I don't think a look-
up table implemented in a FPGA-Rom will work.

Thanks a lot!

Zaid Al-Hilli
Guest

Fri Jul 29, 2011 12:41 pm

On Jul 27, 6:09 pm, Rob Gaddi <rga...@technologyhighland.com> wrote:

Quote:

On 7/27/2011 2:19 AM, Zaid Al-Hilli wrote:

Hi all,

I am about implementing a VHDL code but I am facing problem, I have an
exponential operation and I want to run that code op an FPGA board!!

Generally speaking the assignment is: X = (1 / (1+ exp((y + 87. Cool

/
8.5)));

Would you please help me in that?

Many thanks in advance...

Zaid

Yeah, bound the range of y sufficiently that you can implement the
entire thing in a RAM lookup table.

--
Rob Gaddi, Highland Technology
Email address is currently out of order

Thanks a lot!

Exponential code in VHDL

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