[Libclc-dev] [PATCH] libclc/math: Add cospi
Jeroen Ketema
j.ketema at imperial.ac.uk
Tue Dec 16 07:41:52 PST 2014
> On 16 Dec 2014, at 15:29, Aaron Watry <awatry at gmail.com> wrote:
>
> On Mon, Dec 15, 2014 at 5:25 PM, Jeroen Ketema <j.ketema at imperial.ac.uk> wrote:
>>
>> Hi Aaron,
>>
>> Comments inline.
>>
>>> On 15 Dec 2014, at 23:14, Aaron Watry <awatry at gmail.com> wrote:
>>>
>>> Ported from the libclc/amd-builtins branch
>>>
>>> Signed-off-by: Aaron Watry <awatry at gmail.com>
>>> ---
>>> generic/include/clc/clc.h | 1 +
>>> generic/include/clc/math/cospi.h | 3 ++
>>> generic/include/clc/math/cospi.inc | 1 +
>>> generic/lib/SOURCES | 1 +
>>> generic/lib/math/cospi.cl | 96 ++++++++++++++++++++++++++++++++++++++
>>> generic/lib/math/sincospiF_piby4.h | 57 ++++++++++++++++++++++
>>> 6 files changed, 159 insertions(+)
>>> create mode 100644 generic/include/clc/math/cospi.h
>>> create mode 100644 generic/include/clc/math/cospi.inc
>>> create mode 100644 generic/lib/math/cospi.cl
>>> create mode 100644 generic/lib/math/sincospiF_piby4.h
>>>
>>> diff --git a/generic/include/clc/clc.h b/generic/include/clc/clc.h
>>> index bd92fdb..bff6ddd 100644
>>> --- a/generic/include/clc/clc.h
>>> +++ b/generic/include/clc/clc.h
>>> @@ -38,6 +38,7 @@
>>> #include <clc/math/atan2.h>
>>> #include <clc/math/copysign.h>
>>> #include <clc/math/cos.h>
>>> +#include <clc/math/cospi.h>
>>> #include <clc/math/ceil.h>
>>> #include <clc/math/exp.h>
>>> #include <clc/math/exp10.h>
>>> diff --git a/generic/include/clc/math/cospi.h b/generic/include/clc/math/cospi.h
>>> new file mode 100644
>>> index 0000000..427733b
>>> --- /dev/null
>>> +++ b/generic/include/clc/math/cospi.h
>>> @@ -0,0 +1,3 @@
>>> +#define __CLC_BODY <clc/math/cospi.inc>
>>> +#include <clc/math/gentype.inc>
>>> +#undef __CLC_BODY
>>> diff --git a/generic/include/clc/math/cospi.inc b/generic/include/clc/math/cospi.inc
>>> new file mode 100644
>>> index 0000000..1e786cf
>>> --- /dev/null
>>> +++ b/generic/include/clc/math/cospi.inc
>>> @@ -0,0 +1 @@
>>> +_CLC_OVERLOAD _CLC_DECL __CLC_GENTYPE cospi(__CLC_GENTYPE a);
>>> diff --git a/generic/lib/SOURCES b/generic/lib/SOURCES
>>> index b76fec9..2b9426e 100644
>>> --- a/generic/lib/SOURCES
>>> +++ b/generic/lib/SOURCES
>>> @@ -57,6 +57,7 @@ math/atan.cl
>>> math/atan2.cl
>>> math/copysign.cl
>>> math/cos.cl
>>> +math/cospi.cl
>>> math/exp.cl
>>> math/exp10.cl
>>> math/fmax.cl
>>> diff --git a/generic/lib/math/cospi.cl b/generic/lib/math/cospi.cl
>>> new file mode 100644
>>> index 0000000..666deb7
>>> --- /dev/null
>>> +++ b/generic/lib/math/cospi.cl
>>> @@ -0,0 +1,96 @@
>>> +/*
>>> + * Copyright (c) 2014 Advanced Micro Devices, Inc.
>>> + *
>>> + * Permission is hereby granted, free of charge, to any person obtaining a copy
>>> + * of this software and associated documentation files (the "Software"), to deal
>>> + * in the Software without restriction, including without limitation the rights
>>> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
>>> + * copies of the Software, and to permit persons to whom the Software is
>>> + * furnished to do so, subject to the following conditions:
>>> + *
>>> + * The above copyright notice and this permission notice shall be included in
>>> + * all copies or substantial portions of the Software.
>>> + *
>>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
>>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
>>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
>>> + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
>>> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
>>> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
>>> + * THE SOFTWARE.
>>> + */
>>> +
>>> +#include <clc/clc.h>
>>> +
>>> +#include "math.h"
>>> +#include "sincos_helpers.h"
>>> +#include "sincospiF_piby4.h"
>>> +#include "../clcmacro.h"
>>> +
>>> +_CLC_OVERLOAD _CLC_DEF float cospi(float x)
>>> +{
>>> + int ix = as_int(x) & 0x7fffffff;
>>> + float ax = as_float(ix);
>>> + int iax = (int)ax;
>>> + float r = ax - iax;
>>> + int xodd = iax & 0x1 ? 0x80000000 : 0;
>>> +
>>> + // Initialize with return for +-Inf and NaN
>>> + int ir = 0x7fc00000;
>>> +
>>> + // 2^24 <= |x| < Inf, the result is always even integer
>>> + ir = ix < 0x7f800000 ? 0x3f800000 : ir;
>>> +
>>> + // 2^23 <= |x| < 2^24, the result is always integer
>>> + ir = ix < 0x4b800000 ? xodd | 0x3f800000 : ir;
>>> +
>>> + // 0x1.0p-7 <= |x| < 2^23, result depends on which 0.25 interval
>>> +
>>> + // r < 1.0
>>> + float a = 1.0f - r;
>>> + int e = 1;
>>> + int s = xodd ^ 0x80000000;
>>> +
>>> + // r <= 0.75
>>> + int c = r <= 0.75f;
>>> + a = c ? r - 0.5f : a;
>>> + e = c ? 0 : e;
>>> +
>>> + // r < 0.5
>>> + c = r < 0.5f;
>>> + a = c ? 0.5f - r : a;
>>> + s = c ? xodd : s;
>>> +
>>> + // r <= 0.25
>>> + c = r <= 0.25f;
>>> + a = c ? r : a;
>>> + e = c ? 1 : e;
>>> +
>>> + float2 t = sincosf_piby4(a * M_PI_F);
>>> + int jr = s ^ as_int(e ? t.hi : t.lo);
>>> +
>>> + ir = ix < 0x4b000000 ? jr : ir;
>>> +
>>> + return as_float(ir);
>>> +}
>>> +
>>> +
>>> +_CLC_UNARY_VECTORIZE(_CLC_OVERLOAD _CLC_DEF, float, cospi, float);
>>> +
>>> +#ifdef cl_khr_fp64
>>> +
>>> +#pragma OPENCL EXTENSION cl_khr_fp64 : enable
>>> +
>>> +#define __CLC_FUNCTION __clc_cos_intrinsic
>>> +#define __CLC_INTRINSIC “llvm.cos"
>>
>> Does llvm.cos give sufficient precision for double, or is the intention to leave double as it is for now?
>>
>
> I honestly don't know if llvm.cos gives sufficient precision for
> doubles here. I didn't see any precision notes in the SI ISA guide,
> so until we either have some unit tests for doubles or maybe if Tom
> sees this, I can't really answer that. There is a cospi(double)
> implementation in the amd builtins that were released recently, but I
> haven't attempted to port that yet. I was assuming that because
> cos(double) used __clc_cos_intrinsic, it was probably safe to use it
> for cospi(double) as well... although it's also possible that
> cos(double) isn't precise enough either.
AFAIK, Tom didn’t try to fix-up the double implementation of cos, but
only the float one. So, whatever applies there is likely to apply here
as well.
> One of these days, we need to extend the generated piglit tests to
> test double for inputs/outputs for builtins (that should give us
> decent test coverage of doubles without too much effort, at least for
> devices that support doubles). I have been focusing on other things
> first (basically getting all of the float builtins implemented so that
> cppamp-driver-ng, clBLAS, clFFT, and their unit/precision tests start
> working).
>
>>> +#include <clc/math/unary_intrin.inc>
>>> +#undef __CLC_FUNCTION
>>> +#undef __CLC_INTRINSIC
>>> +
>>> +_CLC_OVERLOAD _CLC_DEF double cospi(double x) {
>>> + return __clc_cos_intrinsic(x*M_PI);
>>> +}
>>> +
>>> +_CLC_UNARY_VECTORIZE(_CLC_OVERLOAD _CLC_DEF, double, cospi, double);
>>> +
>>> +#endif
>>> diff --git a/generic/lib/math/sincospiF_piby4.h b/generic/lib/math/sincospiF_piby4.h
>>> new file mode 100644
>>> index 0000000..3274d90
>>> --- /dev/null
>>> +++ b/generic/lib/math/sincospiF_piby4.h
>>> @@ -0,0 +1,57 @@
>>> +/*
>>> + * Copyright (c) 2014 Advanced Micro Devices, Inc.
>>> + *
>>> + * Permission is hereby granted, free of charge, to any person obtaining a copy
>>> + * of this software and associated documentation files (the "Software"), to deal
>>> + * in the Software without restriction, including without limitation the rights
>>> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
>>> + * copies of the Software, and to permit persons to whom the Software is
>>> + * furnished to do so, subject to the following conditions:
>>> + *
>>> + * The above copyright notice and this permission notice shall be included in
>>> + * all copies or substantial portions of the Software.
>>> + *
>>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
>>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
>>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
>>> + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
>>> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
>>> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
>>> + * THE SOFTWARE.
>>> + */
>>> +
>>> +// Evaluate single precisions in and cos of value in interval [-pi/4, pi/4]
>>> +inline float2
>>> +sincosf_piby4(float x)
>>
>>
>> Would it be possible to start prefixing the internal functions like these with some standard prefix (__libclc_ or something like that). Just the be sure they do not clash with the user’s namespace?
>
> Sounds reasonable.
>
>>
>> Also by C99’s definition of inline, you would also need to provide a non-inlined variant to make sure linking always succeeds; did you also meant to add __attribute__((always_inline)) ?
>
> Yeah, I did mean to add the attribute. Instead of coding that
> directly, I'd like to use the _CLC_INLINE macro from <clc/clcfunc.h>.
> Sound good?
Sounds good to me.
Jeroen
>
> --Aaron
>
>>
>> Jeroen
>>
>>
>>> +{
>>> + // Taylor series for sin(x) is x - x^3/3! + x^5/5! - x^7/7! ...
>>> + // = x * (1 - x^2/3! + x^4/5! - x^6/7! ...
>>> + // = x * f(w)
>>> + // where w = x*x and f(w) = (1 - w/3! + w^2/5! - w^3/7! ...
>>> + // We use a minimax approximation of (f(w) - 1) / w
>>> + // because this produces an expansion in even powers of x.
>>> +
>>> + // Taylor series for cos(x) is 1 - x^2/2! + x^4/4! - x^6/6! ...
>>> + // = f(w)
>>> + // where w = x*x and f(w) = (1 - w/2! + w^2/4! - w^3/6! ...
>>> + // We use a minimax approximation of (f(w) - 1 + w/2) / (w*w)
>>> + // because this produces an expansion in even powers of x.
>>> +
>>> + const float sc1 = -0.166666666638608441788607926e0F;
>>> + const float sc2 = 0.833333187633086262120839299e-2F;
>>> + const float sc3 = -0.198400874359527693921333720e-3F;
>>> + const float sc4 = 0.272500015145584081596826911e-5F;
>>> +
>>> + const float cc1 = 0.41666666664325175238031e-1F;
>>> + const float cc2 = -0.13888887673175665567647e-2F;
>>> + const float cc3 = 0.24800600878112441958053e-4F;
>>> + const float cc4 = -0.27301013343179832472841e-6F;
>>> +
>>> + float x2 = x * x;
>>> +
>>> + float2 ret;
>>> + ret.x = mad(x*x2, mad(x2, mad(x2, mad(x2, sc4, sc3), sc2), sc1), x);
>>> + ret.y = mad(x2*x2, mad(x2, mad(x2, mad(x2, cc4, cc3), cc2), cc1), mad(x2, -0.5f, 1.0f));
>>> + return ret;
>>> +}
>>> +
>>> --
>>> 2.1.0
>>>
>>>
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