Re: Are f.p. manipulation functions only used in initialization?

In article <m2wsmj1mh2.fsf@xxxxxxxxx>,
Charles Coldwell <coldwell@xxxxxxxxx> wrote:

The comment next to _FPU_EXTENDED should be written in a bold,
blinking, red font. You will screw up all of the libm routines (such
as cos, sin, exp, log) if you change the FPU precision.

Since many fortran compilers allow you to manipulate the x87
precision, I don't think this is the case -- one commonly used
commercial compiler sets it to 64 bits *by default*.

If you want exact IEEE answers, this is only one of many things you
need to worry about.

Also, the x87 is used a lot less on x86-64 than x86.

I've also seen comments that glibc's libm only works in 1 rounding
mode. That is changed a lot less frequently than the x87 precision.

-- greg



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