Convert 0x1234 To 0x11223344 - C++ - Stack Overflow

This can be done using SSE2 as follows:

void ExpandSSE2(unsigned __int64 in, unsigned __int64 &outLo, unsigned __int64 &outHi) { __m128i const mask = _mm_set1_epi16((short)0xF00F); __m128i const mul0 = _mm_set1_epi16(0x0011); __m128i const mul1 = _mm_set1_epi16(0x1000); __m128i v; v = _mm_cvtsi64_si128(in); // Move the 64-bit value to a 128-bit register v = _mm_unpacklo_epi8(v, v); // 0x12 -> 0x1212 v = _mm_and_si128(v, mask); // 0x1212 -> 0x1002 v = _mm_mullo_epi16(v, mul0); // 0x1002 -> 0x1022 v = _mm_mulhi_epu16(v, mul1); // 0x1022 -> 0x0102 v = _mm_mullo_epi16(v, mul0); // 0x0102 -> 0x1122 outLo = _mm_extract_epi64(v, 0); outHi = _mm_extract_epi64(v, 1); }

Of course you’d want to put the guts of the function in an inner loop and pull out the constants. You will also want to skip the x64 registers and load values directly into 128-bit SSE registers. For an example of how to do this, refer to the SSE2 implementation in the performance test below.

At its core, there are five instructions, which perform the operation on four color values at a time. So, that is only about 1.25 instructions per color value. It should also be noted that SSE2 is available anywhere x64 is available.

Performance tests for an assortment of the solutions here A few people have mentioned that the only way to know what's faster is to run the code, and this is unarguably true. So I've compiled a few of the solutions into a performance test so we can compare apples to apples. I chose solutions which I felt were significantly different from the others enough to require testing. All the solutions read from memory, operate on the data, and write back to memory. In practice some of the SSE solutions will require additional care around the alignment and handling cases when there aren't another full 16 bytes to process in the input data. The code I tested is x64 compiled under release using Visual Studio 2013 running on a 4+ GHz Core i7.

Here are my results:

ExpandOrig: 56.234 seconds // From asker's original question ExpandSmallLUT: 30.209 seconds // From Dmitry's answer ExpandLookupSmallOneLUT: 33.689 seconds // from Dmitry's answer ExpandLookupLarge: 51.312 seconds // A straightforward lookup table ExpandAShelly: 43.829 seconds // From AShelly's answer ExpandAShellyMulOp: 43.580 seconds // AShelly's answer with an optimization ExpandSSE4: 17.854 seconds // My original SSE4 answer ExpandSSE4Unroll: 17.405 seconds // My original SSE4 answer with loop unrolling ExpandSSE2: 17.281 seconds // My current SSE2 answer ExpandSSE2Unroll: 17.152 seconds // My current SSE2 answer with loop unrolling

In the test results above you'll see I included the asker's code, three lookup table implementations including the small lookup table implementation proposed in Dmitry's answer. AShelly's solution is included too, as well as a version with an optimization I made (an operation can be eliminated). I included my original SSE4 implementation, as well as a superior SSE2 version I made later (now reflected as the answer), as well as unrolled versions of both since they were the fastest here, and I wanted to see how much unrolling sped them up. I also included an SSE4 implementation of AShelly's answer.

So far I have to declare myself the winner. But the source is below, so anyone can test it out on their platform, and include their own solution into the testing to see if they've made a solution that's even faster.

#define DATA_SIZE_IN ((unsigned)(1024 * 1024 * 128)) #define DATA_SIZE_OUT ((unsigned)(2 * DATA_SIZE_IN)) #define RERUN_COUNT 500 #include <cstdlib> #include <ctime> #include <iostream> #include <utility> #include <emmintrin.h> // SSE2 #include <tmmintrin.h> // SSSE3 #include <smmintrin.h> // SSE4 void ExpandOrig(unsigned char const *in, unsigned char const *past, unsigned char *out) { unsigned u, v; do { // Read in data u = *(unsigned const*)in; v = u >> 16; u &= 0x0000FFFF; // Do computation u = (u & 0x00FF) << 4 | (u & 0x000F) | (u & 0x0FF0) << 8 | (u & 0xFF00) << 12 | (u & 0xF000) << 16; v = (v & 0x00FF) << 4 | (v & 0x000F) | (v & 0x0FF0) << 8 | (v & 0xFF00) << 12 | (v & 0xF000) << 16; // Store data *(unsigned*)(out) = u; *(unsigned*)(out + 4) = v; in += 4; out += 8; } while (in != past); } unsigned LutLo[256], LutHi[256]; void MakeLutLo(void) { for (unsigned i = 0, x; i < 256; ++i) { x = i; x = ((x & 0xF0) << 4) | (x & 0x0F); x |= (x << 4); LutLo[i] = x; } } void MakeLutHi(void) { for (unsigned i = 0, x; i < 256; ++i) { x = i; x = ((x & 0xF0) << 20) | ((x & 0x0F) << 16); x |= (x << 4); LutHi[i] = x; } } void ExpandLookupSmall(unsigned char const *in, unsigned char const *past, unsigned char *out) { unsigned u, v; do { // Read in data u = *(unsigned const*)in; v = u >> 16; u &= 0x0000FFFF; // Do computation u = LutHi[u >> 8] | LutLo[u & 0xFF]; v = LutHi[v >> 8] | LutLo[v & 0xFF]; // Store data *(unsigned*)(out) = u; *(unsigned*)(out + 4) = v; in += 4; out += 8; } while (in != past); } void ExpandLookupSmallOneLUT(unsigned char const *in, unsigned char const *past, unsigned char *out) { unsigned u, v; do { // Read in data u = *(unsigned const*)in; v = u >> 16; u &= 0x0000FFFF; // Do computation u = ((LutLo[u >> 8] << 16) | LutLo[u & 0xFF]); v = ((LutLo[v >> 8] << 16) | LutLo[v & 0xFF]); // Store data *(unsigned*)(out) = u; *(unsigned*)(out + 4) = v; in += 4; out += 8; } while (in != past); } unsigned LutLarge[256 * 256]; void MakeLutLarge(void) { for (unsigned i = 0; i < (256 * 256); ++i) LutLarge[i] = LutHi[i >> 8] | LutLo[i & 0xFF]; } void ExpandLookupLarge(unsigned char const *in, unsigned char const *past, unsigned char *out) { unsigned u, v; do { // Read in data u = *(unsigned const*)in; v = u >> 16; u &= 0x0000FFFF; // Do computation u = LutLarge[u]; v = LutLarge[v]; // Store data *(unsigned*)(out) = u; *(unsigned*)(out + 4) = v; in += 4; out += 8; } while (in != past); } void ExpandAShelly(unsigned char const *in, unsigned char const *past, unsigned char *out) { unsigned u, v, w, x; do { // Read in data u = *(unsigned const*)in; v = u >> 16; u &= 0x0000FFFF; // Do computation w = (((u & 0xF0F) * 0x101) & 0xF000F) + (((u & 0xF0F0) * 0x1010) & 0xF000F00); x = (((v & 0xF0F) * 0x101) & 0xF000F) + (((v & 0xF0F0) * 0x1010) & 0xF000F00); w += w * 0x10; x += x * 0x10; // Store data *(unsigned*)(out) = w; *(unsigned*)(out + 4) = x; in += 4; out += 8; } while (in != past); } void ExpandAShellyMulOp(unsigned char const *in, unsigned char const *past, unsigned char *out) { unsigned u, v; do { // Read in data u = *(unsigned const*)in; v = u >> 16; u &= 0x0000FFFF; // Do computation u = ((((u & 0xF0F) * 0x101) & 0xF000F) + (((u & 0xF0F0) * 0x1010) & 0xF000F00)) * 0x11; v = ((((v & 0xF0F) * 0x101) & 0xF000F) + (((v & 0xF0F0) * 0x1010) & 0xF000F00)) * 0x11; // Store data *(unsigned*)(out) = u; *(unsigned*)(out + 4) = v; in += 4; out += 8; } while (in != past); } void ExpandSSE4(unsigned char const *in, unsigned char const *past, unsigned char *out) { __m128i const mask0 = _mm_set1_epi16((short)0x8000), mask1 = _mm_set1_epi8(0x0F), mul = _mm_set1_epi16(0x0011); __m128i u, v, w, x; do { // Read input into low 8 bytes of u and v u = _mm_load_si128((__m128i const*)in); v = _mm_unpackhi_epi8(u, u); // Expand each single byte to two bytes u = _mm_unpacklo_epi8(u, u); // Do it again for v w = _mm_srli_epi16(u, 4); // Copy the value into w and shift it right half a byte x = _mm_srli_epi16(v, 4); // Do it again for v u = _mm_blendv_epi8(u, w, mask0); // Select odd bytes from w, and even bytes from v, giving the the desired value in the upper nibble of each byte v = _mm_blendv_epi8(v, x, mask0); // Do it again for v u = _mm_and_si128(u, mask1); // Clear the all the upper nibbles v = _mm_and_si128(v, mask1); // Do it again for v u = _mm_mullo_epi16(u, mul); // Multiply each 16-bit value by 0x0011 to duplicate the lower nibble in the upper nibble of each byte v = _mm_mullo_epi16(v, mul); // Do it again for v // Write output _mm_store_si128((__m128i*)(out ), u); _mm_store_si128((__m128i*)(out + 16), v); in += 16; out += 32; } while (in != past); } void ExpandSSE4Unroll(unsigned char const *in, unsigned char const *past, unsigned char *out) { __m128i const mask0 = _mm_set1_epi16((short)0x8000), mask1 = _mm_set1_epi8(0x0F), mul = _mm_set1_epi16(0x0011); __m128i u0, v0, w0, x0, u1, v1, w1, x1, u2, v2, w2, x2, u3, v3, w3, x3; do { // Read input into low 8 bytes of u and v u0 = _mm_load_si128((__m128i const*)(in )); u1 = _mm_load_si128((__m128i const*)(in + 16)); u2 = _mm_load_si128((__m128i const*)(in + 32)); u3 = _mm_load_si128((__m128i const*)(in + 48)); v0 = _mm_unpackhi_epi8(u0, u0); // Expand each single byte to two bytes u0 = _mm_unpacklo_epi8(u0, u0); // Do it again for v v1 = _mm_unpackhi_epi8(u1, u1); // Do it again u1 = _mm_unpacklo_epi8(u1, u1); // Again for u1 v2 = _mm_unpackhi_epi8(u2, u2); // Again for v1 u2 = _mm_unpacklo_epi8(u2, u2); // Again for u2 v3 = _mm_unpackhi_epi8(u3, u3); // Again for v2 u3 = _mm_unpacklo_epi8(u3, u3); // Again for u3 w0 = _mm_srli_epi16(u0, 4); // Copy the value into w and shift it right half a byte x0 = _mm_srli_epi16(v0, 4); // Do it again for v w1 = _mm_srli_epi16(u1, 4); // Again for u1 x1 = _mm_srli_epi16(v1, 4); // Again for v1 w2 = _mm_srli_epi16(u2, 4); // Again for u2 x2 = _mm_srli_epi16(v2, 4); // Again for v2 w3 = _mm_srli_epi16(u3, 4); // Again for u3 x3 = _mm_srli_epi16(v3, 4); // Again for v3 u0 = _mm_blendv_epi8(u0, w0, mask0); // Select even bytes from w, and odd bytes from v, giving the the desired value in the upper nibble of each byte v0 = _mm_blendv_epi8(v0, x0, mask0); // Do it again for v u1 = _mm_blendv_epi8(u1, w1, mask0); // Again for u1 v1 = _mm_blendv_epi8(v1, x1, mask0); // Again for v1 u2 = _mm_blendv_epi8(u2, w2, mask0); // Again for u2 v2 = _mm_blendv_epi8(v2, x2, mask0); // Again for v2 u3 = _mm_blendv_epi8(u3, w3, mask0); // Again for u3 v3 = _mm_blendv_epi8(v3, x3, mask0); // Again for v3 u0 = _mm_and_si128(u0, mask1); // Clear the all the upper nibbles v0 = _mm_and_si128(v0, mask1); // Do it again for v u1 = _mm_and_si128(u1, mask1); // Again for u1 v1 = _mm_and_si128(v1, mask1); // Again for v1 u2 = _mm_and_si128(u2, mask1); // Again for u2 v2 = _mm_and_si128(v2, mask1); // Again for v2 u3 = _mm_and_si128(u3, mask1); // Again for u3 v3 = _mm_and_si128(v3, mask1); // Again for v3 u0 = _mm_mullo_epi16(u0, mul); // Multiply each 16-bit value by 0x0011 to duplicate the lower nibble in the upper nibble of each byte v0 = _mm_mullo_epi16(v0, mul); // Do it again for v u1 = _mm_mullo_epi16(u1, mul); // Again for u1 v1 = _mm_mullo_epi16(v1, mul); // Again for v1 u2 = _mm_mullo_epi16(u2, mul); // Again for u2 v2 = _mm_mullo_epi16(v2, mul); // Again for v2 u3 = _mm_mullo_epi16(u3, mul); // Again for u3 v3 = _mm_mullo_epi16(v3, mul); // Again for v3 // Write output _mm_store_si128((__m128i*)(out ), u0); _mm_store_si128((__m128i*)(out + 16), v0); _mm_store_si128((__m128i*)(out + 32), u1); _mm_store_si128((__m128i*)(out + 48), v1); _mm_store_si128((__m128i*)(out + 64), u2); _mm_store_si128((__m128i*)(out + 80), v2); _mm_store_si128((__m128i*)(out + 96), u3); _mm_store_si128((__m128i*)(out + 112), v3); in += 64; out += 128; } while (in != past); } void ExpandSSE2(unsigned char const *in, unsigned char const *past, unsigned char *out) { __m128i const mask = _mm_set1_epi16((short)0xF00F), mul0 = _mm_set1_epi16(0x0011), mul1 = _mm_set1_epi16(0x1000); __m128i u, v; do { // Read input into low 8 bytes of u and v u = _mm_load_si128((__m128i const*)in); v = _mm_unpackhi_epi8(u, u); // Expand each single byte to two bytes u = _mm_unpacklo_epi8(u, u); // Do it again for v u = _mm_and_si128(u, mask); v = _mm_and_si128(v, mask); u = _mm_mullo_epi16(u, mul0); v = _mm_mullo_epi16(v, mul0); u = _mm_mulhi_epu16(u, mul1); // This can also be done with a right shift of 4 bits, but this seems to mesure faster v = _mm_mulhi_epu16(v, mul1); u = _mm_mullo_epi16(u, mul0); v = _mm_mullo_epi16(v, mul0); // write output _mm_store_si128((__m128i*)(out ), u); _mm_store_si128((__m128i*)(out + 16), v); in += 16; out += 32; } while (in != past); } void ExpandSSE2Unroll(unsigned char const *in, unsigned char const *past, unsigned char *out) { __m128i const mask = _mm_set1_epi16((short)0xF00F), mul0 = _mm_set1_epi16(0x0011), mul1 = _mm_set1_epi16(0x1000); __m128i u0, v0, u1, v1; do { // Read input into low 8 bytes of u and v u0 = _mm_load_si128((__m128i const*)(in )); u1 = _mm_load_si128((__m128i const*)(in + 16)); v0 = _mm_unpackhi_epi8(u0, u0); // Expand each single byte to two bytes u0 = _mm_unpacklo_epi8(u0, u0); // Do it again for v v1 = _mm_unpackhi_epi8(u1, u1); // Do it again u1 = _mm_unpacklo_epi8(u1, u1); // Again for u1 u0 = _mm_and_si128(u0, mask); v0 = _mm_and_si128(v0, mask); u1 = _mm_and_si128(u1, mask); v1 = _mm_and_si128(v1, mask); u0 = _mm_mullo_epi16(u0, mul0); v0 = _mm_mullo_epi16(v0, mul0); u1 = _mm_mullo_epi16(u1, mul0); v1 = _mm_mullo_epi16(v1, mul0); u0 = _mm_mulhi_epu16(u0, mul1); v0 = _mm_mulhi_epu16(v0, mul1); u1 = _mm_mulhi_epu16(u1, mul1); v1 = _mm_mulhi_epu16(v1, mul1); u0 = _mm_mullo_epi16(u0, mul0); v0 = _mm_mullo_epi16(v0, mul0); u1 = _mm_mullo_epi16(u1, mul0); v1 = _mm_mullo_epi16(v1, mul0); // write output _mm_store_si128((__m128i*)(out ), u0); _mm_store_si128((__m128i*)(out + 16), v0); _mm_store_si128((__m128i*)(out + 32), u1); _mm_store_si128((__m128i*)(out + 48), v1); in += 32; out += 64; } while (in != past); } void ExpandAShellySSE4(unsigned char const *in, unsigned char const *past, unsigned char *out) { __m128i const zero = _mm_setzero_si128(), v0F0F = _mm_set1_epi32(0x0F0F), vF0F0 = _mm_set1_epi32(0xF0F0), v0101 = _mm_set1_epi32(0x0101), v1010 = _mm_set1_epi32(0x1010), v000F000F = _mm_set1_epi32(0x000F000F), v0F000F00 = _mm_set1_epi32(0x0F000F00), v0011 = _mm_set1_epi32(0x0011); __m128i u, v, w, x; do { // Read in data u = _mm_load_si128((__m128i const*)in); v = _mm_unpackhi_epi16(u, zero); u = _mm_unpacklo_epi16(u, zero); // original source: ((((a & 0xF0F) * 0x101) & 0xF000F) + (((a & 0xF0F0) * 0x1010) & 0xF000F00)) * 0x11; w = _mm_and_si128(u, v0F0F); x = _mm_and_si128(v, v0F0F); u = _mm_and_si128(u, vF0F0); v = _mm_and_si128(v, vF0F0); w = _mm_mullo_epi32(w, v0101); // _mm_mullo_epi32 is what makes this require SSE4 instead of SSE2 x = _mm_mullo_epi32(x, v0101); u = _mm_mullo_epi32(u, v1010); v = _mm_mullo_epi32(v, v1010); w = _mm_and_si128(w, v000F000F); x = _mm_and_si128(x, v000F000F); u = _mm_and_si128(u, v0F000F00); v = _mm_and_si128(v, v0F000F00); u = _mm_add_epi32(u, w); v = _mm_add_epi32(v, x); u = _mm_mullo_epi32(u, v0011); v = _mm_mullo_epi32(v, v0011); // write output _mm_store_si128((__m128i*)(out ), u); _mm_store_si128((__m128i*)(out + 16), v); in += 16; out += 32; } while (in != past); } int main() { unsigned char *const indat = new unsigned char[DATA_SIZE_IN ], *const outdat0 = new unsigned char[DATA_SIZE_OUT], *const outdat1 = new unsigned char[DATA_SIZE_OUT], * curout = outdat0, * lastout = outdat1, * place; unsigned start, stop; place = indat + DATA_SIZE_IN - 1; do { *place = (unsigned char)rand(); } while (place-- != indat); MakeLutLo(); MakeLutHi(); MakeLutLarge(); for (unsigned testcount = 0; testcount < 1000; ++testcount) { // Solution posted by the asker start = clock(); for (unsigned rerun = 0; rerun < RERUN_COUNT; ++rerun) ExpandOrig(indat, indat + DATA_SIZE_IN, curout); stop = clock(); std::cout << "ExpandOrig:\t\t\t" << (((stop - start) / 1000) / 60) << ':' << (((stop - start) / 1000) % 60) << ":." << ((stop - start) % 1000) << std::endl; std::swap(curout, lastout); // Dmitry's small lookup table solution start = clock(); for (unsigned rerun = 0; rerun < RERUN_COUNT; ++rerun) ExpandLookupSmall(indat, indat + DATA_SIZE_IN, curout); stop = clock(); std::cout << "ExpandSmallLUT:\t\t\t" << (((stop - start) / 1000) / 60) << ':' << (((stop - start) / 1000) % 60) << ":." << ((stop - start) % 1000) << std::endl; std::swap(curout, lastout); if (memcmp(outdat0, outdat1, DATA_SIZE_OUT)) std::cout << "INCORRECT OUTPUT" << std::endl; // Dmitry's small lookup table solution using only one lookup table start = clock(); for (unsigned rerun = 0; rerun < RERUN_COUNT; ++rerun) ExpandLookupSmallOneLUT(indat, indat + DATA_SIZE_IN, curout); stop = clock(); std::cout << "ExpandLookupSmallOneLUT:\t" << (((stop - start) / 1000) / 60) << ':' << (((stop - start) / 1000) % 60) << ":." << ((stop - start) % 1000) << std::endl; std::swap(curout, lastout); if (memcmp(outdat0, outdat1, DATA_SIZE_OUT)) std::cout << "INCORRECT OUTPUT" << std::endl; // Large lookup table solution start = clock(); for (unsigned rerun = 0; rerun < RERUN_COUNT; ++rerun) ExpandLookupLarge(indat, indat + DATA_SIZE_IN, curout); stop = clock(); std::cout << "ExpandLookupLarge:\t\t" << (((stop - start) / 1000) / 60) << ':' << (((stop - start) / 1000) % 60) << ":." << ((stop - start) % 1000) << std::endl; std::swap(curout, lastout); if (memcmp(outdat0, outdat1, DATA_SIZE_OUT)) std::cout << "INCORRECT OUTPUT" << std::endl; // AShelly's Interleave bits by Binary Magic Numbers solution start = clock(); for (unsigned rerun = 0; rerun < RERUN_COUNT; ++rerun) ExpandAShelly(indat, indat + DATA_SIZE_IN, curout); stop = clock(); std::cout << "ExpandAShelly:\t\t\t" << (((stop - start) / 1000) / 60) << ':' << (((stop - start) / 1000) % 60) << ":." << ((stop - start) % 1000) << std::endl; std::swap(curout, lastout); if (memcmp(outdat0, outdat1, DATA_SIZE_OUT)) std::cout << "INCORRECT OUTPUT" << std::endl; // AShelly's Interleave bits by Binary Magic Numbers solution optimizing out an addition start = clock(); for (unsigned rerun = 0; rerun < RERUN_COUNT; ++rerun) ExpandAShellyMulOp(indat, indat + DATA_SIZE_IN, curout); stop = clock(); std::cout << "ExpandAShellyMulOp:\t\t" << (((stop - start) / 1000) / 60) << ':' << (((stop - start) / 1000) % 60) << ":." << ((stop - start) % 1000) << std::endl; std::swap(curout, lastout); if (memcmp(outdat0, outdat1, DATA_SIZE_OUT)) std::cout << "INCORRECT OUTPUT" << std::endl; // My SSE4 solution start = clock(); for (unsigned rerun = 0; rerun < RERUN_COUNT; ++rerun) ExpandSSE4(indat, indat + DATA_SIZE_IN, curout); stop = clock(); std::cout << "ExpandSSE4:\t\t\t" << (((stop - start) / 1000) / 60) << ':' << (((stop - start) / 1000) % 60) << ":." << ((stop - start) % 1000) << std::endl; std::swap(curout, lastout); if (memcmp(outdat0, outdat1, DATA_SIZE_OUT)) std::cout << "INCORRECT OUTPUT" << std::endl; // My SSE4 solution unrolled start = clock(); for (unsigned rerun = 0; rerun < RERUN_COUNT; ++rerun) ExpandSSE4Unroll(indat, indat + DATA_SIZE_IN, curout); stop = clock(); std::cout << "ExpandSSE4Unroll:\t\t" << (((stop - start) / 1000) / 60) << ':' << (((stop - start) / 1000) % 60) << ":." << ((stop - start) % 1000) << std::endl; std::swap(curout, lastout); if (memcmp(outdat0, outdat1, DATA_SIZE_OUT)) std::cout << "INCORRECT OUTPUT" << std::endl; // My SSE2 solution start = clock(); for (unsigned rerun = 0; rerun < RERUN_COUNT; ++rerun) ExpandSSE2(indat, indat + DATA_SIZE_IN, curout); stop = clock(); std::cout << "ExpandSSE2:\t\t\t" << (((stop - start) / 1000) / 60) << ':' << (((stop - start) / 1000) % 60) << ":." << ((stop - start) % 1000) << std::endl; std::swap(curout, lastout); if (memcmp(outdat0, outdat1, DATA_SIZE_OUT)) std::cout << "INCORRECT OUTPUT" << std::endl; // My SSE2 solution unrolled start = clock(); for (unsigned rerun = 0; rerun < RERUN_COUNT; ++rerun) ExpandSSE2Unroll(indat, indat + DATA_SIZE_IN, curout); stop = clock(); std::cout << "ExpandSSE2Unroll:\t\t" << (((stop - start) / 1000) / 60) << ':' << (((stop - start) / 1000) % 60) << ":." << ((stop - start) % 1000) << std::endl; std::swap(curout, lastout); if (memcmp(outdat0, outdat1, DATA_SIZE_OUT)) std::cout << "INCORRECT OUTPUT" << std::endl; // AShelly's Interleave bits by Binary Magic Numbers solution implemented using SSE2 start = clock(); for (unsigned rerun = 0; rerun < RERUN_COUNT; ++rerun) ExpandAShellySSE4(indat, indat + DATA_SIZE_IN, curout); stop = clock(); std::cout << "ExpandAShellySSE4:\t\t" << (((stop - start) / 1000) / 60) << ':' << (((stop - start) / 1000) % 60) << ":." << ((stop - start) % 1000) << std::endl; std::swap(curout, lastout); if (memcmp(outdat0, outdat1, DATA_SIZE_OUT)) std::cout << "INCORRECT OUTPUT" << std::endl; } delete[] indat; delete[] outdat0; delete[] outdat1; return 0; }

NOTE:

I had an SSE4 implementation here initially. I found a way to implement this using SSE2, which is better because it will run on more platforms. The SSE2 implementation is also faster. So, the solution presented at the top is now the SSE2 implementation and not the SSE4 one. The SSE4 implementation can still be seen in the performance tests or in the edit history.