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Date:      Mon, 14 Oct 2002 21:40:28 -0700
From:      Steve Kargl <sgk@troutmask.apl.washington.edu>
To:        Tim Robbins <tjr@FreeBSD.ORG>
Cc:        Kris Kennaway <kris@obsecurity.org>, Andrew Gallatin <gallatin@cs.duke.edu>, Nate Lawson <nate@root.org>, current@FreeBSD.ORG
Subject:   Re: X problems & 5.0... -RELEASE?
Message-ID:  <20021015044028.GA17862@troutmask.apl.washington.edu>
In-Reply-To: <20021015123926.A76421@dilbert.robbins.dropbear.id.au>
References:  <15786.50928.826403.959175@grasshopper.cs.duke.edu> <Pine.BSF.4.21.0210141053301.33371-100000@root.org> <15787.1474.824422.286474@grasshopper.cs.duke.edu> <20021014200045.GA51207@xor.obsecurity.org> <20021015123926.A76421@dilbert.robbins.dropbear.id.au>

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On Tue, Oct 15, 2002 at 12:39:26PM +1000, Tim Robbins wrote:
> On Mon, Oct 14, 2002 at 01:00:46PM -0700, Kris Kennaway wrote:
> 
> [...]
> > Did anyone test -current with the various FP test suites people posted
> > about last week?
> 
> Yes. I ran paranoia from http://cm.bell-labs.com/netlib/paranoia/ and
> found that FP arithmethic is satisfactory when -O is not used, and no
> -march or -mcpu options are used.
> 
> However, compiling with -O causes a lot of failures.

Are you using an intel cpu?  You need to add -ffloat-store
to get the correct results due to the 80 bit FPU registers.
Otherwise, intermediate results are stored with higher
precision.

Both of the following commands:

  f77 -o a -ffloat-store dpara.f
  f77 -o a -ffloat-store -O dpara.f

yield

  No failures, defects nor flaws have been discovered.
  Rounding appears to conform to the proposed IEEE standard  P754
  except possibly for Double Rounding during Gradual Underflow.
  The arithmetic diagnosed appears to be Excellent!
  End of Test.

Otherwise, optimization yields your results.

> 
> Here are the messages:
> 
> Seeking Underflow thresholds UfThold and E0.
> DEFECT:  Difference underflows at a higher threshold than products.
> ...
> Can `Z = -Y' overflow?
> Trying it on Y = -inf .
> finds a FLAW:  -(-Y) differs from Y.
> ...
> FAILURE:  Comparisons involving +--inf, +-inf
> and +-4.94066e-324 are confused by Overflow.
> ...
> DEFECT:  Badly unbalanced range; UfThold * V = -inf
>         is too far from 1.
> 
> SERIOUS DEFECT:    X / X differs from 1 when X = -inf
>   instead, X / X - 1/2 - 1/2 = nan .
> 
> 
> The summary message:
> 
> The number of  FAILUREs  encountered =       1.
> The number of  SERIOUS DEFECTs  discovered = 1.
> The number of  DEFECTs  discovered =         2.
> The number of  FLAWs  discovered =           1.
> 
> The arithmetic diagnosed has unacceptable Serious Defects.
> Potentially fatal FAILURE may have spoiled this program's subsequent diagnoses.

-- 
Steve

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