Atividade 1.

atividade2/avx.c

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+/*
+Exemplo de código AVX utilizando Intel instrinsics e gcc built-in functions
+
+Compile usando:
+gcc avx.c -o avx -mavx -O3
+
+
+http://www.songho.ca/misc/sse/sse.html
+
+https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gcc/X86-Built-in-Functions.html#X86-Built-in-Functions
+https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gcc/Vector-Extensions.html#Vector-Extensions
+https://software.intel.com/sites/landingpage/IntrinsicsGuide/
+https://msdn.microsoft.com/en-us/library/26td21ds.aspx
+
+AVX
+https://software.intel.com/en-us/articles/introduction-to-intel-advanced-vector-extensions/
+
+*/
+
+#include <stdio.h>
+#include <immintrin.h> // AVX
+
+__m256 negPixel(float *pixel)
+{
+  __m256 p = _mm256_load_ps(pixel);
+  __m256 max = _mm256_set1_ps(255);
+  return _mm256_sub_ps(max, p);
+}
+
+int main (int argc, char *argv[])
+{
+  float *im = (float*)_mm_malloc (sizeof(float) * 64, 32); //aloca um vetor de 32 bytes (256 bits) alinhado em endereços múltiplos de 16 bytes.
+  float *im2 = (float*)_mm_malloc (sizeof(float) * 64, 32);
+
+  int i = 0;
+  for (i = 0; i < 64; ++i) {
+    im[i] = i;
+  }
+
+  for(i = 0; i <= 56; i+=8) 
+  {
+    __m256 pixel = negPixel(&im[i]);
+    _mm256_store_ps(&im2[i], pixel);
+  }
+
+  for (i = 0; i < 64; ++i) {
+    printf("%f\t~~~~~~> %f\n", im[i], im2[i]);
+  }
+
+  _mm_free(im);
+  _mm_free(im2);
+
+  return 0;
+}