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Re: NaN's origin

E. Robert Tisdale
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klaas wrote:

> How does a NaN occur?
> Can it occur if a float get's to large?
> my matrix multiplication algorhytm gives NaN's.
> There obviously is no 0.0/0.0 statement there.
> with double used there is no problem... ???

What Every Scientist Should Know About Floating-Point Arithmetic

The IEEE Standard, Special Quantities:

On some floating-point hardware every bit pattern represents a valid
floating-point number. The IBM System/370 is an example of this. On the
other hand, the VAX(TM) reserves some bit patterns to represent special
numbers called reserved operands. This idea goes back to the CDC 6600,
which had bit patterns for the special quantities INDEFINITE and INFINITY.

The IEEE standard continues in this tradition and has NaNs and
infinities (NaN stands for Not a Number). Without any special
quantities, there is no good way to handle exceptional situations like
taking the square root of a negative number, other than aborting
computation. Under IBM System/370 FORTRAN,

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