Dear Fred
On 9 Apr 98 at 23:22, you wrote:
> There is a Visual C++ runtime library function called _controlfp()
> which sets the IEEE floating-point status word. The syntax is
> _controlfp(value, mask); the mask indicates which bits of the status
> word you want to change. There are lots of constants defined for
> various parts of this word. In order to set round-to-nearest mode,
> the syntax would be:
>
> _controlfp(_RC_NEAR, _MCW_RC);
>
> The other rounding mode choices are _RC_CHOP, _RC_UP, and _RC_DOWN.
Thank you very much for your clarification.
I am aware about this function but I doubt ROOT should change the
default setting.
Another question whether ROOT should supply some "common" method to
give the user an opportunity to change this option on his / her own
via TSystem class.
Since ROOT is multi-platform package it should be understood how
this method will be implemented for the rest supported platforms too.
For the time being I would advice those finding it is essential
to control the rounding "by hand" call this function himself
/herself from his/her method.
From another hand I'd like to call your attention that the C / C++
docs says:
Floating to Integral
====================
When an object of floating type is converted to an integral type,
the fractional part is truncated. No rounding takes place in the
conversion process. Truncation means that a number like 1.3 is
converted to 1, and -1.3 is converted to -1.
THAT'S TRUE for ANY CURRENT MathCPU bits setting (it is a LAW for
each platform / compiler implementation and NO hardware/ CPU flag /
mask are "allowed" to change it)
And just another LAW:
Integral to Floating
====================
When an object of integral type is converted to a floating type and
the original value cannot be represented exactly, the result is
either the next higher or the next lower representable value.
Valery
=================================================================
Dr. Valeri Faine (Fine)
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