simd

I have many function which use the same constant __m128i values. For example: const __m128i K8 = _mm_setr_epi8(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16); const __m128i K16 = _mm_setr_epi16(1, 2, 3, 4, 5, 6, 7, 8); const __m128i K32 = _mm_setr_epi32(1, 2, 3, 4); So I want to store all these constants in an one place. But there is a problem: I perform checking of existed CPU extension in run time. If the CPU doesn't support for example SSE (or AVX) than will be a program crash during constants initialization. So is it possible to initialize these constants without using of SSE?

I have a function that copies binary data from one area to another, but only if the bytes are different from a specific value. Here is a code sample: void copy_if(char* src, char* dest, size_t size, char ignore) { for (size_t i = 0; i < size; ++i) { if (src[i] != ignore) dest[i] = src[i]; } } The problem is that this is too slow for my current need. Is there a way to obtain the same result in a faster way? Update: Based on answers I tried two new implementations: void copy_if_vectorized(const uint8_t* src, uint8_t* dest, size_t size, char ignore) { for (size_t i = 0; i < size; ++i) { char

I want to add the four components of an SSE register to get a single float. This is how I do it now: float a[4]; _mm_storeu_ps(a, foo128); float x = a[0] + a[1] + a[2] + a[3]; Is there an SSE instruction that directly achieves this? You could probably use the HADDPS SSE3 instruction, or its compiler intrinsic _mm_hadd_ps , For example, see http://msdn.microsoft.com/en-us/library/yd9wecaa(v=vs.80).aspx If you have two registers v1 and v2 : v = _mm_hadd_ps(v1, v2); v = _mm_hadd_ps(v, v); Now, v[0] contains the sum of v1's components, and v[1] contains the sum of v2's components. If you want your

I have the following function I'm trying to write an AXV version for: void hashids_shuffle(char *str, size_t str_length, char *salt, size_t salt_length) { size_t i, j, v, p; char temp; if (!salt_length) { return; } for (i = str_length - 1, v = 0, p = 0; i > 0; --i, ++v) { v %= salt_length; p += salt[v]; j = (salt[v] + v + p) % i; temp = str[i]; str[i] = str[j]; str[j] = temp; } } I'm trying to vectorize v %= salt_length; . I want to initialize a vector that contains numbers from 0 to str_length in order to use SVML's _mm_rem_epu64 in order to calculate v for each loop iteration. How do I

Assume a CUDA kernel executed by a single warp (for simplicity) reaches an if - else statement, where 20 of the threads within the warp satisfy condition and 32 - 20 = 12 threads do not: if (condition){ statement1; // executed by 20 threads else{ statement2; // executed by 12 threads } According to the CUDA C Programming Guide : A warp executes one common instruction at a time [...] if threads of a warp diverge via a data-dependent conditional branch, the warp serially executes each branch path taken, disabling threads that are not on that path, and when all paths complete, the threads