sse

I am trying to make the fastest possible high quality RNG. Having read http://xorshift.di.unimi.it/ , xorshift128+ seems like a good option. The C code is #include <stdint.h> uint64_t s[ 2 ]; uint64_t next(void) { uint64_t s1 = s[ 0 ]; const uint64_t s0 = s[ 1 ]; s[ 0 ] = s0; s1 ^= s1 << 23; // a return ( s[ 1 ] = ( s1 ^ s0 ^ ( s1 >> 17 ) ^ ( s0 >> 26 ) ) ) + s0; // b, c } I am not an SSE/AVX expert sadly but my CPU supports SSE4.1 / SSE4.2 / AVX / F16C / FMA3 / XOP instructions. How could you use these to speed up this code (assuming you want to make billions of such random numbers) and what

I'm looking for the most efficient method of flipping the sign on all four floats packed in an SSE register. I have not found an intrinsic for doing this in the Intel Architecture software dev manual. Below are the things I've already tried. For each case I looped over the code 10 billion times and got the wall-time indicated. I'm trying to at least match 4 seconds it takes my non-SIMD approach, which is using just the unary minus operator. [48 sec] _mm_sub_ps( _mm_setzero_ps(), vec ); [32 sec] _mm_mul_ps( _mm_set1_ps( -1.0f ), vec ); [9 sec] union NegativeMask { int intRep; float fltRep; }

There already is a question on this, but it was closed as "ambiguous" so I'm opening a new one - I've found the answer, maybe it will help others too. The question is: how do you write a sequence of assembly code to initialize an XMM register with a 128-bit immediate (constant) value? Norbert P. Just wanted to add that one can read about generating various constants using assembly in Agner Fog's manual Optimizing subroutines in assembly language , Generating constants, section 13.8, page 134. Paul R You can do it like this, with just one movaps instruction: .section .rodata # put your

I'm new to AVX programming. I have a register which needs to be shuffled. I want to shuffle several bytes from a 256-bit register, R1, to an empty register R2. I want to define a mask which tells the shuffle operation which byte from the old register(R1) should be copied at which place in the new register. The mask should look like this(Src:Byte Pos in R1, Target:Byte Pos in R2): {(0,0),(1,1),(1,4),(2,5),...} This means several bytes are copied twice. I'm not 100% sure which function I should use for this. I tried a bit with these two AVX functions, the second just uses 2 lanes. __m256 _mm256

If I want to do a bitwise equality test between two __m128i variables, am I required to use an SSE instruction or can I use == ? If not, which SSE instruction should I use? Although using _mm_movemask_epi8 is one solution, if you have a processor with SSE4.1 I think a better solution is to use an instruction which sets the zero or carry flag in the FLAGS register. This saves a test or cmp instruction . To do this you could do this: if(_mm_test_all_ones(_mm_cmpeq_epi8(v1,v2))) { //v0 == v1 } Edit: as Paul R pointed out _mm_test_all_ones generates two instructions: pcmpeqd and ptest . With _mm

I am trying to implement SSE vectorization on a piece of code for which I need my 1D array to be 16 byte memory aligned. However, I have tried several ways to allocate 16byte memory aligned data but it ends up being 4byte memory aligned. I have to work with the Intel icc compiler. This is a sample code I am testing with: #include <stdio.h> #include <stdlib.h> void error(char *str) { printf("Error:%s\n",str); exit(-1); } int main() { int i; //float *A=NULL; float *A = (float*) memalign(16,20*sizeof(float)); //align // if (posix_memalign((void **)&A, 16, 20*sizeof(void*)) != 0) // error("Cannot