search for: denormals

Hi all, While reviewing a recent clang documentation change, I became aware of an issue with the way that clang is handling FP denormals. There is currently some support for variations in the way denormals are handled, but it isn't consistent across architectures and generally feels kind of half-baked. I'd like to discuss possible solutions to this problem. First, there is a clang command line option: -fdenormal-fp-mat...

...dev at lists.llvm.org> wrote: > > > Do we need an ftz fast-math flag? > > > This would be useful for matching a handful of AMDGPU instructions (a fmad > that only always flushes being the most important). We have a dedicated > intrinsic to allow flushing in this case when denormals are enabled > +1 For FTZ/DAZ, we're currently getting cases like this incorrect: %add = fadd nnan ninf nsz float %a, 0.000000e+00 That cannot be safely optimized to 'a' with FTZ/DAZ enabled. Although, there's admittedly a small chance of problems, since a following FP opera...

Our processor also has some issues regarding the handling of denormals - scalar and vector - and we ran into a related problem only a few days ago. The v3.8 compiler has done a lot of good work on optimisations for floating-point math, but ironically one of them broke our implementation of 'nextafterf'. The desired code fragment (FP32) is: float xAbs = fa...

...o:speex-dev-bounces at xiph.org] Im Auftrag von Jeff Wallace Betreff: Re: [Speex-dev] High CPU usage If you are compiling with SSE and/or SSE2 instructions enabled, you could consider enabling the floating point "Flush-to-zero" mode and maybe (if supported on the processor) enable "denormals are zero". The flush-to-zero is probably the more important of the two. http://software.intel.com/en-us/articles/x87-and-sse-floating-point-assists-in-ia-32-flush-to-zero-ftz-and-denormals-are-zero-daz/ On Wed, Sep 23, 2009 at 4:06 AM, Jean-Marc Valin <jean-marc.valin at usherbrooke....

IEEE-754R defines a normal floating point number as: 2.1.38 normal number: For a particular format, a finite non-zero floating-point number with magnitude greater than or equal to a minimum bemin value, where b is the radix. Normal numbers can use the full precision available in a format. In this standard, zero is neither normal nor subnormal. This implies that a denormal is not a normal number.

...tics and my > analysis is that NEON's only problem is the Flush-to-zero behaviour, > which is non-compliant. > > NEON deals with NaNs and Infs in the way specified by the standard and > should not cause any concern to us. But we don't seem to have a flag > specifically to denormals, so I think using the UnsafeMath is the > safest option for now. > > On 11 February 2016 at 01:15, Hal Finkel <hfinkel at anl.gov> wrote: >> nsz >> No Signed Zeros - Allow optimizations to treat the sign of a zero argument or result as insignificant. > > In both...

...one and a way to reproduce, and I'll have a look at them. >> > > > It is not the vectorizer that is the issue, it is the ARM backend that currently translates vectorized floating point IR to NEON instructions (it should scalarize it if desired to do so - i.e. if people care about denormals). To fix this issue one would have to fix the backend: i.e not declare v4f32 et al as legal (under a flag). As to making this predicated on fast math flags on operations (something like no-denormals - i don’t think we have that in the IR yet - we only have no nan, no infinite, no signed zeros, etc)...

----- Original Message ----- > From: "Renato Golin" <renato.golin at linaro.org> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "James Molloy" <James.Molloy at arm.com>, "Nadav Rotem" <nrotem at apple.com>, "Arnold Schwaighofer" > <aschwaighofer at apple.com>, "LLVM Dev" <llvm-dev at

| For programs that have mixed precision requirements for floating point | operations we probably need to do this according to the fast math flags. | Until we get there, a good first step would probably be to provide a | global option similar to -enable-no-infs-fp-math that specifies if | denormals should be allowed or not. This would allow the user to specify | the precision requirements, without the need to alter with the feature | flags of a specific piece of hardware. Hi, sorry for coming in late on this. Firstly, I think what you mean is "if denormals should be required to be prese...

Hello R users, My problem is that the data I've got is in the minimum number of columns with each ward (geographic area) appearing multiple times. The first 30 terms look like this > HHum02 CASW Btype Yr CO2Group NumVeh 170597 00CCFA CARS 2002 C 2 170598 00CCFA CARS 2002 D 2 170599 00CCFA CARS 2002 E 22 170600 00CCFA CARS 2002

I am building a relatively trivial application to try to learn my way around Rails. I am having difficulty understanding how to navigate a heavily denormalized hierarchy. Could someone direct me to a bare-bones explanation of using rails to navigate database hierarchies? I am an experienced developer. Most of my work has been desktop client server, high performance, or server to server

...So, we can't vectorize FP loops without either -ffast-math or -mfpmath=neon, but we want to tell the users that they could get more performance out of their compiler if either option was chosen. If I force the need for -ffast-math, many other deviations from IEEE-754 will be allowed, not just denormals, so you're left with either slow or potentially bad results. Using -mfpmath hits the right spot, but is less known and is not plugged in yet. Vectorizing FP loops is a correctness problem in NEON (and I assume SSE), so it would be good to be safe. But I take it it's not a serious correctne...

...vant IR to each one and a way to reproduce, and I'll have a look at them. > It is not the vectorizer that is the issue, it is the ARM backend that currently translates vectorized floating point IR to NEON instructions (it should scalarize it if desired to do so - i.e. if people care about denormals). To fix this issue one would have to fix the backend: i.e not declare v4f32 et al as legal (under a flag). As to making this predicated on fast math flags on operations (something like no-denormals - i don’t think we have that in the IR yet - we only have no nan, no infinite, no signed zeros, etc)...

Hi, I''m new to RoR and exploring its use with an existing application. One thing I can''t seem to find much detail on is using database triggers. All RoR examples and tutorials I''ve seen are very basic saving data back to a single table. My use case includes a somewhat denormalized DB that uses triggers to store data in multiple tables on occassion. I currently

...t="utf-8" Hi Tanmay, >Does compiling speex API with DISABLE_FLOAT_API and DISABLE_VBR solve the >problem? I remember that this fixed the problem. But at that time I also needed VBR so this was not an option. As far as I know, it is related to some calculations that involve float denormals that cause the high CPU usage. Today I'm still using the following code before speex_encoder_init and erverything works great: // fix denormals performance issue // http://software.intel.com/en-us/articles/x87-and-sse-floating-point-assists-in-ia-32-flush-to-zero-ftz-and-denormals-are-zero-da...

On 12 October 2016 at 15:05, Hal Finkel <hfinkel at anl.gov> wrote: > This is something we need to understand. No, there's not always an error bar. With FMA formation and without non-IEEE-compliant optimizations (i.e. fast-math), the optimized answer should be identical to the non-optimized answer. What about architectures that this is never respected, like Darwin? In the general

On Fri, Jun 21, 2013 at 5:11 PM, Erik Schnetter <schnetter at cct.lsu.edu>wrote: > On Fri, Jun 21, 2013 at 7:54 AM, David Tweed <david.tweed at arm.com> wrote: > >> | LLVM does not currently have special lowering handling for round(), and >> I'll propose a patch to add that, but the larger question is this: should >> fast-math change the tie-breaking

...rams that have mixed precision requirements for floating point > | operations we probably need to do this according to the fast math flags. > | Until we get there, a good first step would probably be to provide a > | global option similar to -enable-no-infs-fp-math that specifies if > | denormals should be allowed or not. This would allow the user to specify > | the precision requirements, without the need to alter with the feature > | flags of a specific piece of hardware. > > Hi, sorry for coming in late on this. Firstly, I think what you mean is "if denormals should be r...

On 7 June 2013 08:48, Tobias Grosser <tobias at grosser.es> wrote: > When to set which subtarget feature is a policy decision, where I honestly > don't have any opinion on for clang. The best is probably to mirror the gcc > behavior on linux targets. > Not really, since GCC has no special behaviour for Darwin, AFAIK. My change will only generate SP-FP on NEON for A5 and A8

----- Original Message ----- > > On Fri, Jun 21, 2013 at 5:11 PM, Erik Schnetter < > schnetter at cct.lsu.edu > wrote: > > > > > > > On Fri, Jun 21, 2013 at 7:54 AM, David Tweed < david.tweed at arm.com > > wrote: > > > > > > > | LLVM does not currently have special lowering handling for round(), > | and >