# Re: Computing exp(z)

*From*: gh14tq5@xxxxxxxxx*Date*: 19 May 2005 16:42:24 -0700

Hi Richard,

Richard E Maine wrote:

> One would sort of expect that to be the way of things.

>

> If a user can correctly duplicate the complete functionality of an

> intrinsic procedure and do so faster than the intrinsic, then either

>

> 1. The intrinsic was implemented pretty sloppily.

I don't know how the intrinsic is implemented.

>

> 2. The user is exceptionally talented and compiler vendors should

> consider hiring him.

>

2. This is definitely not the case. Half the time, I'm amazed my

programs even work at all.

> or

>

> 3. It didn't actually correctly duplicate the complete functionality.

>

> Case 3 is probably the most likely, though the others are certainly

> possible and have probably happened at one time or other.

>

> Of course, there are times when the complete functionality isn't

needed.

> That's a different story. If you know the range of values that will

be

> used and don't have to fuss with edge cases, maybe this can turn into

> speedups. Likewise you might be able to trade off some accuracy for

> speed if the answer doesn't have to be accurate to the last bit.

I think this is the case. I do not expect my implementation to be

accurate for all values of z. But, in my program, the range of z

values is limited. In this range, the substitute seems to give

identical results to the intrinsic. My problem is basically an inverse

Fourier transform ( int(f(w)exp(-j*w*t)dw) ) that has been slighly

deformed into the complex plane for small values (in magnitude) of the

variable w to avoid some problem points. For large values of w, w is

limited to the real axis. t is real and and limited in magnitude.

John

.

**References**:**Computing exp(z)***From:*gh14tq5@xxxxxxxxx

**Re: Computing exp(z)***From:*Ron Shepard

**Re: Computing exp(z)***From:*Tim Prince

**Re: Computing exp(z)***From:*Richard E Maine

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