Opened 5 years ago

Closed 5 years ago

#4629 closed enhancement (fixed)

Remove NUMERICFLAGS

Reported by: Algunenano Owned by: Algunenano
Priority: medium Milestone: PostGIS 3.1.0
Component: postgis Version: master
Keywords: Cc:

Description

While looking at other flags, I noticed the existence of NUMERICFLAGS which activates -ffloat-store if available.

I have 2 issues with this:

  • It's only used in some parts (liblwgeom/ and libpgcommon/), while other folders know nothing about it.
  • It's bad for precision (you voluntarily accept less precision) and, I guess, performance since you are not using the registers.

As of today, I get the same results for clang (without that option) and with GCC (which has that flag available), so I suggest dropping it altogether and in the case that we find some difference in an output, try to change it to allow both 80bit and 64bit precision in double operations.

Change History (2)

comment:1 by komzpa, 5 years ago

It became obsolete since we adopted C99 which implies -fexcess-precision=standard, which has the same executive effect as —ffloat-store but does not define how to do it ("by writing to registers"). I +1 to remove NUMERICFLAGS.

If you want to race for raw computation speed try making -ffast-math pass tests once again - it did for 2.5.

comment:2 by Raúl Marín <git@…>, 5 years ago

Resolution: fixed
Status: assignedclosed

In 92fc725/git:

Remove NUMERICFLAGS

Closes #4629

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