[Octave-bug-tracker] [bug #42589] Inaccurate results with the colon operator

[Rik]

Follow-up Comment #23, bug #42589 (project octave):

@Michael: I think the decision was made to go for consistency versus accuracy.
 Not all platforms will support extra floating point precision in their
hardware-based floating point units.  To have the same results across
different versions of Octave, different hardware, and different compilers
Octave does it's very best best to enforce the IEEE standard (only 64 bits).

For example, configure.ac includes the following about --enable-float-truncate
option which gets used for MinGW and Cygwin platforms.


### When compiling math for x87, problems may arise in some code comparing
### floating-point intermediate results.  The root cause is the extra
precision
### (~80 bits) of x87 co-processor registers versus the IEEE standard 64
bits.
### Generally, storing the result in a local volatile variable forces a
### truncation back to 64 bits, but it also degrades performance.
### Thus, we provide a FLOAT_TRUNCATE macro that may be defined to "volatile"
### when compiling for x87 target, or left empty for modern SSE math, that
### doesn't suffer from this problem at all.




    _______________________________________________________

Reply to this item at:

  <http://savannah.gnu.org/bugs/?42589>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.gnu.org/