| |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <assert.h> |
| |
| typedef signed int Int; |
| typedef unsigned int UInt; |
| typedef unsigned long long int Addr64; |
| typedef unsigned char UChar; |
| typedef unsigned long int UWord; |
| |
| static inline UInt ROL32 ( UInt x, UInt n ) { |
| assert(n != 0); |
| n &= 31; |
| x = (x << n) | (x >> (32-n)); |
| return x; |
| } |
| |
| ////////////////////////////////////////////////////////// |
| |
| typedef |
| struct { |
| Addr64 ga; |
| Int nbytes; |
| UChar* bytes; |
| UChar* actual; |
| } |
| GuestBytes; |
| |
| GuestBytes* read_one ( FILE* f ) |
| { |
| Int r; |
| UInt i; |
| UInt esum, csum; |
| |
| GuestBytes* gb = malloc(sizeof(GuestBytes)); |
| assert(gb); |
| |
| if (feof(f)) return NULL; |
| assert(!ferror(f)); |
| |
| r= fscanf(f, "GuestBytes %llx %d ", &gb->ga, &gb->nbytes); |
| if (0) printf("r = %d\n", r); |
| assert(r == 2); |
| |
| assert(gb->ga != 0); |
| assert(gb->nbytes > 0); |
| assert(gb->nbytes < 5000); // let's say |
| |
| Int nToAlloc = gb->nbytes + (gb->ga & 3); |
| |
| gb->bytes = malloc( gb->nbytes + nToAlloc); |
| gb->actual = gb->bytes + (gb->ga & 3); |
| assert(gb->bytes); |
| |
| csum = 0; |
| for (i = 0; i < gb->nbytes; i++) { |
| UInt b; |
| r= fscanf(f, "%02x ", &b); |
| assert(r == 1); |
| gb->actual[i] = b; |
| csum = (csum << 1) ^ b; |
| } |
| |
| r= fscanf(f, " %08x\n", &esum); |
| assert(r == 1); |
| |
| assert(esum == csum); |
| |
| return gb; |
| } |
| |
| ////////////////////////////////////////////////////////// |
| |
| void apply_to_all ( FILE* f, |
| void(*fn)( GuestBytes*, void* ), |
| void* opaque ) |
| { |
| while (!feof(f)) { |
| GuestBytes* gb = read_one(f); |
| if (0) printf("got %llu %d\n", gb->ga, gb->nbytes); |
| fn( gb, opaque ); |
| free(gb->bytes); |
| free(gb); |
| } |
| } |
| |
| ////////////////////////////////////////////////////////// |
| |
| UInt hash_const_zero ( GuestBytes* gb ) { |
| return 0; |
| } |
| |
| UInt hash_sum ( GuestBytes* gb ) { |
| UInt i, sum = 0; |
| for (i = 0; i < gb->nbytes; i++) |
| sum += (UInt)gb->actual[i]; |
| return sum; |
| } |
| |
| UInt hash_rol ( GuestBytes* gb ) { |
| UInt i, sum = 0; |
| for (i = 0; i < gb->nbytes; i++) { |
| sum ^= (UInt)gb->actual[i]; |
| sum = ROL32(sum,7); |
| } |
| return sum; |
| } |
| |
| static UInt cand0 ( GuestBytes* gb ) |
| { |
| UWord addr = (UWord)gb->actual; |
| UWord len = gb->nbytes; |
| UInt sum = 0; |
| /* pull up to 4-alignment */ |
| while ((addr & 3) != 0 && len >= 1) { |
| UChar* p = (UChar*)addr; |
| sum = (sum << 8) | (UInt)p[0]; |
| addr++; |
| len--; |
| } |
| /* vectorised + unrolled */ |
| while (len >= 16) { |
| UInt* p = (UInt*)addr; |
| sum = ROL32(sum ^ p[0], 13); |
| sum = ROL32(sum ^ p[1], 13); |
| sum = ROL32(sum ^ p[2], 13); |
| sum = ROL32(sum ^ p[3], 13); |
| addr += 16; |
| len -= 16; |
| } |
| /* vectorised fixup */ |
| while (len >= 4) { |
| UInt* p = (UInt*)addr; |
| sum = ROL32(sum ^ p[0], 13); |
| addr += 4; |
| len -= 4; |
| } |
| /* scalar fixup */ |
| while (len >= 1) { |
| UChar* p = (UChar*)addr; |
| sum = ROL32(sum ^ (UInt)p[0], 19); |
| addr++; |
| len--; |
| } |
| return sum; |
| } |
| |
| static UInt cand1 ( GuestBytes* gb ) |
| { |
| UWord addr = (UWord)gb->actual; |
| UWord len = gb->nbytes; |
| UInt sum1 = 0, sum2 = 0; |
| /* pull up to 4-alignment */ |
| while ((addr & 3) != 0 && len >= 1) { |
| UChar* p = (UChar*)addr; |
| sum1 = (sum1 << 8) | (UInt)p[0]; |
| addr++; |
| len--; |
| } |
| /* vectorised + unrolled */ |
| while (len >= 16) { |
| UInt* p = (UInt*)addr; |
| UInt w; |
| w = p[0]; sum1 = ROL32(sum1 ^ w, 31); sum2 += w; |
| w = p[1]; sum1 = ROL32(sum1 ^ w, 31); sum2 += w; |
| w = p[2]; sum1 = ROL32(sum1 ^ w, 31); sum2 += w; |
| w = p[3]; sum1 = ROL32(sum1 ^ w, 31); sum2 += w; |
| addr += 16; |
| len -= 16; |
| sum1 ^= sum2; |
| } |
| /* vectorised fixup */ |
| while (len >= 4) { |
| UInt* p = (UInt*)addr; |
| UInt w = p[0]; |
| sum1 = ROL32(sum1 ^ w, 31); sum2 += w; |
| addr += 4; |
| len -= 4; |
| sum1 ^= sum2; |
| } |
| /* scalar fixup */ |
| while (len >= 1) { |
| UChar* p = (UChar*)addr; |
| UInt w = (UInt)p[0]; |
| sum1 = ROL32(sum1 ^ w, 31); sum2 += w; |
| addr++; |
| len--; |
| } |
| return sum1 + sum2; |
| } |
| |
| static UInt adler32 ( GuestBytes* gb ) |
| { |
| UWord addr = (UWord)gb->actual; |
| UWord len = gb->nbytes; |
| UInt s1 = 1; |
| UInt s2 = 0; |
| UChar* buf = (UChar*)addr; |
| while (len >= 4) { |
| s1 += buf[0]; |
| s2 += s1; |
| s1 += buf[1]; |
| s2 += s1; |
| s1 += buf[2]; |
| s2 += s1; |
| s1 += buf[3]; |
| s2 += s1; |
| buf += 4; |
| len -= 4; |
| } |
| while (len > 0) { |
| s1 += buf[0]; |
| s2 += s1; |
| len--; |
| buf++; |
| } |
| return (s2 << 16) + s1; |
| } |
| |
| |
| |
| |
| ////////////////////////////////////////////////////////// |
| |
| UInt (*theFn)(GuestBytes*) = |
| //hash_const_zero; |
| //hash_sum; |
| //hash_rol; |
| //cand0; |
| cand1; |
| //adler32; |
| |
| Int cmp_UInt_ps ( UInt* p1, UInt* p2 ) { |
| if (*p1 < *p2) return -1; |
| if (*p1 > *p2) return 1; |
| return 0; |
| } |
| |
| Int nSetBits ( UInt w ) |
| { |
| Int i, j; |
| j = 0; |
| for (i = 0; i < 32; i++) |
| if (w & (1<<i)) |
| j++; |
| return j; |
| } |
| |
| Int toc_nblocks = 0; |
| Int toc_nblocks_with_zero = 0; |
| double toc_sum_of_avgs = 0.0; |
| |
| void invertBit ( UChar* b, UInt ix, UInt bix ) { |
| b[ix] ^= (1 << bix); |
| } |
| |
| void try_onebit_changes( GuestBytes* gb, void* opaque ) |
| { |
| toc_nblocks++; |
| /* collect up the hash values for all one bit changes of the key, |
| and also that for the unmodified key. Then compute the number |
| of changed bits for all of them. */ |
| UInt hashIx = 0; |
| UInt nHashes = 8 * gb->nbytes; |
| UInt* hashes = malloc( nHashes * sizeof(UInt) ); |
| |
| UInt byteIx, bitIx; |
| UInt hInit, hFinal, hRunning; |
| Int dist, totDist = 0, nNoDist = 0; |
| assert(hashes); |
| hInit = theFn( gb ); |
| for (byteIx = 0; byteIx < gb->nbytes; byteIx++) { |
| for (bitIx = 0; bitIx < 8; bitIx++) { |
| |
| invertBit(gb->actual, byteIx, bitIx); |
| //invertBit(gb->actual, byteIx, bitIx ^ 4); |
| |
| hRunning = theFn( gb ); |
| |
| dist = nSetBits(hRunning ^ hInit); |
| totDist += dist; |
| if (dist == 0) nNoDist++; |
| |
| hashes[hashIx++] = hRunning; |
| |
| invertBit(gb->actual, byteIx, bitIx); |
| //invertBit(gb->actual, byteIx, bitIx ^ 4); |
| |
| if (0) printf(" %02d.%d %08x %d\n", |
| byteIx, bitIx, hRunning ^ hInit, dist); |
| } |
| } |
| hFinal = theFn( gb ); |
| assert(hFinal == hInit); |
| assert(hashIx == nHashes); |
| |
| if (nNoDist > 0) |
| printf("%4d measurements, %5.2f avg dist, %2d zeroes\n", |
| (Int)nHashes, (double)totDist / (double)nHashes, nNoDist); |
| else |
| printf("%4d measurements, %5.2f avg dist\n", |
| (Int)nHashes, (double)totDist / (double)nHashes); |
| |
| if (nNoDist > 0) |
| toc_nblocks_with_zero++; |
| |
| toc_sum_of_avgs += (double)totDist / (double)nHashes; |
| |
| free(hashes); |
| } |
| |
| ////////////////////////////////////////////////////////// |
| |
| int main ( void ) |
| { |
| FILE* f = stdin; |
| apply_to_all(f, try_onebit_changes, NULL); |
| printf("\n%d blocks, %d with a zero, %5.2f avg avg\n\n", |
| toc_nblocks, toc_nblocks_with_zero, toc_sum_of_avgs / (double)toc_nblocks ); |
| return 0; |
| } |
| |
| ////////////////////////////////////////////////////////// |
