search for: denormal

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-ma...

...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 oper...

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 = f...

Hi Jeff, Hi Jean-Marc, I first modified the FPU control word to raise an exception whenever a denormal is used. Then I used the debugger to locate the exceptions and added VERY_SMALLs where they seem to fit well. Although I got CPU usage as low as 10%, I seriously lack knowledge of how things work inside speex. So just changing some code is not the best idea for me. My second attempt was to follow...

...umber: 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. In contrast, the current implementation of isNormal in APFloat does treat denormal numbers as normal numbers breaking this definition. This is not just a predicate that has a name that differs from IEEE-754R (which I am fine with), but is an actual name collision with IEEE-...

Hi, > James, is that a correct assessment? Yes, it is also my belief that the only way ARMv7 NEON differs from IEEE754 is lack of denormal support. James > On 11 Feb 2016, at 10:53, Renato Golin <renato.golin at linaro.org> wrote: > > Hal, > > I had a read on the ARM ARM about VFP and SIMD FP semantics and my > analysis is that NEON's only problem is the Flush-to-zero behaviour, > which is non-compli...

...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 pres...

...most appropriate but it's just not working using the default formula: http://r.789695.n4.nabble.com/file/n3729817/Screenshot-*getting-started.txt_%28%7E-1Projects-OSS_general%29_-_gedit.png Look forward to learning, Robin -- View this message in context: http://r.789695.n4.nabble.com/Denormalize-data-tp3729817p3729817.html Sent from the R help mailing list archive at Nabble.com.

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 interprocess work in large scale systems (8K plus users). Howe...

...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 correctn...

...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...

..., 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 use IBM DB2 9. Can anyone explain how to use DB triggers in a complimentary fashion with RoR? Or, I''m assuming that because I could not find examples of how to work with triggers, the more elegant Ro...

...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-d...

...respected, like Darwin? In the general case, indeed, optimisation levels should not change the IEEE representation and the tests should be deterministic. But we can't guarantee this will always be the case. > We still do see cross-system discrepancies sometimes because of differences in denormal handling, but on the same system that should be consistent (aside, perhaps, from compiler-level constant-folding issues). But the test-suite doesn't run on a single system, nor it has one reference_output for each system. cheers, --renato

...ct result, and not obtaining this exact result is surprising. For example, I would expect that adding/multiplying two small integers gives the exact result, or that fmin/fmax give the correct result if no nans are involved, or that comparisons yield the correct answer (again in the absence of nans, denormalized numbers etc.). The case here -- rint(0.5) -- involves an input that can be represented exactly, and an output that can be represented exactly (0.0). Neither nans, infinities, nor denormalized numbers are involved. In this case I do expect the correct answer, even with full floating point opera...

...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...

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

...btaining this exact result is surprising. For example, I would > expect that adding/multiplying two small integers gives the exact > result, or that fmin/fmax give the correct result if no nans are > involved, or that comparisons yield the correct answer (again in the > absence of nans, denormalized numbers etc.). > > > The case here -- rint(0.5) -- involves an input that can be > represented exactly, and an output that can be represented exactly > (0.0). Neither nans, infinities, nor denormalized numbers are > involved. In this case I do expect the correct answer, even...