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Multiply 64-bit integers using .NET Core's hardware intrinsics


Multiply 64-bit integers using .NET Core's hardware intrinsics

By : Akash Bhowmick
Date : October 25 2020, 07:10 PM
should help you out SIMD vectors aren't single wide integers. The max element width is 64-bit. They're for processing multiple elements in parallel.
x86 doesn't have any instructions for 64x64 => 128-bit SIMD-element multiply, not even with AVX512DQ. (That does provide SIMD 64x64 => 64-bit multiply though, for 2, 4, or 8 elements in parallel.)
code :


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How to use the multiply and accumulate intrinsics in ARM Cortex-a8?

How to use the multiply and accumulate intrinsics in ARM Cortex-a8?


By : jtee
Date : March 29 2020, 07:55 AM
Hope this helps how to use the Multiply-Accumulate intrinsics provided by GCC? , Simply said the vmla instruction does the following:
code :
struct 
{
  float val[4];
} float32x4_t


float32x4_t vmla (float32x4_t a, float32x4_t b, float32x4_t c)
{
  float32x4 result;

  for (int i=0; i<4; i++)
  {
    result.val[i] =  b.val[i]*c.val[i]+a.val[i];
  }

  return result;
}
float32x4_t transform (float32x4_t * matrix, float32x4_t vector)
{
  /* in a perfect world this code would compile into just four instructions */
  float32x4_t result;

  result = vml (matrix[0], vector);
  result = vmla (result, matrix[1], vector);
  result = vmla (result, matrix[2], vector);
  result = vmla (result, matrix[3], vector);

  return result;
}
Processing 32 bit integers on 32 bit hardware and on 64bit hardware, which is faster?

Processing 32 bit integers on 32 bit hardware and on 64bit hardware, which is faster?


By : yu liu
Date : March 29 2020, 07:55 AM
I hope this helps . You should tell on what exact hardware, and what kind of processing.
And more importantly, you should benchmark your application, taking into account that premature optimization is evil.
code :
typedef intfast_t myimportantint_t;
Intel intrinsics : multiply interleaved 8bit values

Intel intrinsics : multiply interleaved 8bit values


By : Ibrahim Slemani
Date : March 29 2020, 07:55 AM
this will help Here is a solution which finds Y,U, and V all at once and only uses vertical operators
To do this I first tranpose four pixels like this
code :
rgbargbargbargba -> rrrrggggbbbbaaaa
row[0] : rrrrggggbbbbaaaa
row[1] : rrrrggggbbbbaaaa
row[2] : rrrrggggbbbbaaaa
ro2[3] : rrrrggggbbbbaaaa
row[0] : rrrrrrrrrrrrrrrr    
row[1] : gggggggggggggggg    
row[2] : bbbbbbbbbbbbbbbb
__m128i t0 = _mm_unpacklo_epi32(row[0], row[1]);
__m128i t1 = _mm_unpacklo_epi32(row[2], row[3]);
__m128i t2 = _mm_unpackhi_epi32(row[0], row[1]);
__m128i t3 = _mm_unpackhi_epi32(row[2], row[3]);
row[0] = _mm_unpacklo_epi64(t0, t1);
row[1] = _mm_unpackhi_epi64(t0, t1);
row[2] = _mm_unpacklo_epi64(t2, t3);
__m128i v_lo[3], v_hi[3];
for(int i=0; i<3; i++) {
    v_lo[i] = _mm_unpacklo_epi8(row[i],_mm_setzero_si128());
    v_hi[i] = _mm_unpackhi_epi8(row[i],_mm_setzero_si128());
}
 short m[9] = {66, 129, 25, -38, -74, 112, 112, -94, -18};
__m128i yuv[3];
for(int i=0; i<3; i++) {
    __m128i yuv_lo, yuv_hi;
    yuv_lo = _mm_add_epi16(_mm_add_epi16(
                   _mm_mullo_epi16(v_lo[0], _mm_set1_epi16(m[3*i+0])),
                   _mm_mullo_epi16(v_lo[1], _mm_set1_epi16(m[3*i+1]))),
                   _mm_mullo_epi16(v_lo[2], _mm_set1_epi16(m[3*i+2])));
    yuv_lo = _mm_add_epi16(yuv_lo, _mm_set1_epi16(128));
    yuv_lo = _mm_srli_epi16(yuv_lo, 8);
    yuv_lo = _mm_add_epi16(yuv_lo, _mm_set1_epi16(16));

    yuv_hi = _mm_add_epi16(_mm_add_epi16(
                   _mm_mullo_epi16(v_hi[0], _mm_set1_epi16(m[3*i+0])),
                   _mm_mullo_epi16(v_hi[1], _mm_set1_epi16(m[3*i+1]))),
                   _mm_mullo_epi16(v_hi[2], _mm_set1_epi16(m[3*i+2])));
    yuv_hi = _mm_add_epi16(yuv_hi, _mm_set1_epi16(128));
    yuv_hi = _mm_srli_epi16(yuv_hi, 8);
    yuv_hi = _mm_add_epi16(yuv_hi, _mm_set1_epi16(16));

    yuv[i] = _mm_packus_epi16(yuv_lo,yuv_hi);
}
FMA intrinsics not working: is it Hardware or Compiler?

FMA intrinsics not working: is it Hardware or Compiler?


By : bam
Date : March 29 2020, 07:55 AM
it fixes the issue One of the quirks of C is that the language indicates that the compiler is to assume a symbol it's not seen before must return int if you call it like a function. Since you didn't include the header that actually defines the signature for _mm_fmadd_ps, you get the strange error about converting int to __m128.
The original organization of the intrinsics headers was to have a unique header per instruction generations, so you had:
code :
mmintrin.h     The original MMX instruction set (deprecated for x64 native)
mm3dnow.h      The AMD 3D Now! instruction set (deprecated for x64 native)
emmintrin.h    SSE (i.e. single-precision 4-wide SIMD)
xmmintrin.h    SSE2 (i.e. double-precision and integer 4-wide SIMD)
pmmintrin.h    SSE3 (the p stands for Prescott)
tmmintrin.h    Supplemental SSE3 (the t stands for Tejas)
smmintrin.h    SSE4.1 (not sure what the s is here for.
               They were added for Penryn but p
               was already used for Prescott)
nmmintrin.h    SSE4.2 (the n stands for Nehalem)
wmmintrin.h    AES (the w stands for Westmere)
How to build 32bit integers from array of 8bit integers using Intel intrinsics?

How to build 32bit integers from array of 8bit integers using Intel intrinsics?


By : Eli
Date : March 29 2020, 07:55 AM
wish of those help As usual, check the disassembly. Then as it turns out, with the compiler I used anyway, that it relies on that data being a compile time constant, and it rearranges it so that it can be loaded easily. If that is actually the case in your real code, this is fine (but then why not use an array of uints to begin with?). But if, as I suspect it is, this is just an example and the actual array with be variable, this is a disaster, just look at it:
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