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Posted 9 Sep 2011
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# Fastest strstr-like function in C!?

, 22 Aug 2016
Tuned function for searching a needle in a haystack
 ```﻿#define ASIZE 256 // ### Boyer-Moore-Horspool algorithm [ long HORSPOOL(y, x, n, m) char *y; char *x; long n; int m; { long i; int a, j, bm_bc[ASIZE]; unsigned char ch; unsigned char lastch; /* Preprocessing */ for (a=0; a < ASIZE; a++) bm_bc[a]=m; for (j=0; j < m-1; j++) { bm_bc[*(unsigned char *)&x[j]]=m-j-1; } /* Searching */ lastch=*(unsigned char *)&x[m-1]; i=0; while (i <= n-m) { ch=*(unsigned char *)&y[i+m-1]; if (ch ==lastch) //if (memcmp(&y[i],x,m-1) == 0) OUTPUT(i); if (memcmp(&y[i],x,m-1) == 0) return(i); i+=bm_bc[ch]; } return(-1); } // Railgun_Ennearch, copyleft 2014-Jan-15, Kaze. // heptarch, noun. // L17. // [from HEPTA- + -ARCH, after TETRARCH noun.] // † 1. A seventh king (see Revelation 17:9–11). Only in L17. // 2. A ruler of one of seven divisions of a country; esp. any of the rulers of the Anglo-Saxon Heptarchy. E19. // /SOED/ // decarch, noun. // Also dekarch. M17. // [Greek dekarkhUs, -os decurion, from deka ten + arkhos leader.] // Greek History. Each of a ruling body of ten. // /SOED/ // diarchy, noun. // Also dyarchy. M19. // [from DI-2 after monarchy.] // A mode of joint government by two; government by two independent authorities; spec. the system of provincial government in India from 1921 to 1937. // /SOED/ // monadic -> mona+ARCH // duadic/dyadic -> dyarchy // triadic -> // quadic/tetradic -> // pentadic -> pentarch // hexadic -> // heptadic/hebdomadic (for 7) -> hepta+ARCH // octadic -> OCTA+ARCHY // enneadic (for 9) -> // decadic (for 10) -> // Caution: For better speed the case 'if (cbPattern==1)' was removed, so Pattern must be longer than 1 char. #define NeedleThreshold2vs4Nonus 9+10 // Should be bigger than 9. BMH2 works up to this value (inclusive), if bigger then BMH4 takes over. char * Railgun_Ennearch (char * pbTarget, char * pbPattern, uint32_t cbTarget, uint32_t cbPattern) { char * pbTargetMax = pbTarget + cbTarget; register uint32_t ulHashPattern; signed long count; unsigned char bm_Horspool_Order2[256*256]; // Bitwise soon... uint32_t i, Gulliver; if (cbPattern > cbTarget) return(NULL); if ( cbPattern<4 ) { // SSE2 i.e. 128bit Assembly rules here: // ... pbTarget = pbTarget+cbPattern; ulHashPattern = ( (*(char *)(pbPattern))<<8 ) + *(pbPattern+(cbPattern-1)); if ( cbPattern==3 ) { for ( ;; ) { if ( ulHashPattern == ( (*(char *)(pbTarget-3))<<8 ) + *(pbTarget-1) ) { if ( *(char *)(pbPattern+1) == *(char *)(pbTarget-2) ) return((pbTarget-3)); } if ( (char)(ulHashPattern>>8) != *(pbTarget-2) ) { pbTarget++; if ( (char)(ulHashPattern>>8) != *(pbTarget-2) ) pbTarget++; } pbTarget++; if (pbTarget > pbTargetMax) return(NULL); } } else { } for ( ;; ) { if ( ulHashPattern == ( (*(char *)(pbTarget-2))<<8 ) + *(pbTarget-1) ) return((pbTarget-2)); if ( (char)(ulHashPattern>>8) != *(pbTarget-1) ) pbTarget++; pbTarget++; if (pbTarget > pbTargetMax) return(NULL); } } else { //if ( cbPattern<4 ) if ( cbPattern<=NeedleThreshold2vs4Nonus ) { // BMH order 2, needle should be >=4: ulHashPattern = *(uint32_t *)(pbPattern); // First four bytes for (i=0; i < 256*256; i++) {bm_Horspool_Order2[i]=0;} for (i=0; i < cbPattern-1; i++) bm_Horspool_Order2[*(unsigned short *)(pbPattern+i)]=1; i=0; while (i <= cbTarget-cbPattern) { Gulliver = 1; // 'Gulliver' is the skip if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+cbPattern-1-1]] != 0 ) { if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+cbPattern-1-1-2]] == 0 ) Gulliver = cbPattern-(2-1)-2; else { if ( *(uint32_t *)&pbTarget[i] == ulHashPattern) { // This fast check ensures not missing a match (for remainder) when going under 0 in loop below: count = cbPattern-4+1; while ( count > 0 && *(uint32_t *)(pbPattern+count-1) == *(uint32_t *)(&pbTarget[i]+(count-1)) ) count = count-4; if ( count <= 0 ) return(pbTarget+i); } } } else Gulliver = cbPattern-(2-1); i = i + Gulliver; //GlobalI++; // Comment it, it is only for stats. } return(NULL); } else { // if ( cbPattern<=NeedleThreshold2vs4Nonus ) // BMH pseudo-order 4, needle should be >=8+2: ulHashPattern = *(uint32_t *)(pbPattern); // First four bytes for (i=0; i < 256*256; i++) {bm_Horspool_Order2[i]=0;} // In line below we "hash" 4bytes to 2bytes i.e. 16bit table, how to compute TOTAL number of BBs, 'cbPattern - Order + 1' is the number of BBs for text 'cbPattern' bytes long, for example, for cbPattern=11 'fastest fox' and Order=4 we have BBs = 11-4+1=8: //"fast" //"aste" //"stes" //"test" //"est " //"st f" //"t fo" //" fox" //for (i=0; i < cbPattern-4+1; i++) bm_Horspool_Order2[( *(unsigned short *)(pbPattern+i+0) + *(unsigned short *)(pbPattern+i+2) ) & ( (1<<16)-1 )]=1; //for (i=0; i < cbPattern-4+1; i++) bm_Horspool_Order2[( (*(uint32_t *)(pbPattern+i+0)>>16)+(*(uint32_t *)(pbPattern+i+0)&0xFFFF) ) & ( (1<<16)-1 )]=1; // Above line is replaced by next one with better hashing: for (i=0; i < cbPattern-4+1; i++) bm_Horspool_Order2[( (*(uint32_t *)(pbPattern+i+0)>>(16-1))+(*(uint32_t *)(pbPattern+i+0)&0xFFFF) ) & ( (1<<16)-1 )]=1; i=0; while (i <= cbTarget-cbPattern) { Gulliver = 1; //if ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2]&0xFFFF) ) & ( (1<<16)-1 )] != 0 ) { // DWORD #1 // Above line is replaced by next one with better hashing: if ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2]>>(16-1))+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2]&0xFFFF) ) & ( (1<<16)-1 )] != 0 ) { // DWORD #1 //if ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) ) & ( (1<<16)-1 )] == 0 ) Gulliver = cbPattern-(2-1)-2-4; else { // Above line is replaced in order to strengthen the skip by checking the middle DWORD,if the two DWORDs are 'ab' and 'cd' i.e. [2x][2a][2b][2c][2d] then the middle DWORD is 'bc'. // The respective offsets (backwards) are: -10/-8/-6/-4 for 'xa'/'ab'/'bc'/'cd'. //if ( ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) ) & ( (1<<16)-1 )] ) < 3 ) Gulliver = cbPattern-(2-1)-2-4-2; else { // Above line is replaced by next one with better hashing: // When using (16-1) right shifting instead of 16 we will have two different pairs (if they are equal), the highest bit being lost do the job especialy for ASCII texts with no symbols in range 128-255. // Example for genomesque pair TT+TT being shifted by (16-1): // T = 01010100 // TT = 01010100 01010100 // TTTT = 01010100 01010100 01010100 01010100 // TTTT>>16 = 00000000 00000000 01010100 01010100 // TTTT>>(16-1) = 00000000 00000000 10101000 10101000 <--- Due to the left shift by 1, the 8th bits of 1st and 2nd bytes are populated - usually they are 0 for English texts & 'ACGT' data. //if ( ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]>>(16-1))+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]>>(16-1))+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]>>(16-1))+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) ) & ( (1<<16)-1 )] ) < 3 ) Gulliver = cbPattern-(2-1)-2-4-2; else { // 'Maximus' uses branched 'if', again. if ( \ ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6 +1]>>(16-1))+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6 +1]&0xFFFF) ) & ( (1<<16)-1 )] ) == 0 \ || ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4 +1]>>(16-1))+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4 +1]&0xFFFF) ) & ( (1<<16)-1 )] ) == 0 \ ) Gulliver = cbPattern-(2-1)-2-4-2 +1; else { // Above line is not optimized (several a SHR are used), we have 5 non-overlapping WORDs, or 3 overlapping WORDs, within 4 overlapping DWORDs so: // [2x][2a][2b][2c][2d] // DWORD #4 // [2a] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]>>16) = !SHR to be avoided! <-- // [2x] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]&0xFFFF) = | // DWORD #3 | // [2b] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]>>16) = !SHR to be avoided! |<-- // [2a] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) = ------------------------ | // DWORD #2 | // [2c] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]>>16) = !SHR to be avoided! |<-- // [2b] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) = --------------------------- | // DWORD #1 | // [2d] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]>>16) = | // [2c] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]&0xFFFF) = ------------------------------ // // So in order to remove 3 SHR instructions the equal extractions are: // DWORD #4 // [2a] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) = !SHR to be avoided! <-- // [2x] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]&0xFFFF) = | // DWORD #3 | // [2b] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) = !SHR to be avoided! |<-- // [2a] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) = ------------------------ | // DWORD #2 | // [2c] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]&0xFFFF) = !SHR to be avoided! |<-- // [2b] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) = --------------------------- | // DWORD #1 | // [2d] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]>>16) = | // [2c] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]&0xFFFF) = ------------------------------ //if ( ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]&0xFFFF)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) ) & ( (1<<16)-1 )] ) < 3 ) Gulliver = cbPattern-(2-1)-2-6; else { // Since the above Decumanus mumbo-jumbo (3 overlapping lookups vs 2 non-overlapping lookups) is not fast enough we go DuoDecumanus or 3x4: // [2y][2x][2a][2b][2c][2d] // DWORD #3 // DWORD #2 // DWORD #1 //if ( ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-8]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-8]&0xFFFF) ) & ( (1<<16)-1 )] ) < 2 ) Gulliver = cbPattern-(2-1)-2-8; else { if ( *(uint32_t *)&pbTarget[i] == ulHashPattern) { // Order 4 [ // Let's try something "outrageous" like comparing with[out] overlap BBs 4bytes long instead of 1 byte back-to-back: // Inhere we are using order 4, 'cbPattern - Order + 1' is the number of BBs for text 'cbPattern' bytes long, for example, for cbPattern=11 'fastest fox' and Order=4 we have BBs = 11-4+1=8: //0:"fast" if the comparison failed here, 'count' is 1; 'Gulliver' is cbPattern-(4-1)-7 //1:"aste" if the comparison failed here, 'count' is 2; 'Gulliver' is cbPattern-(4-1)-6 //2:"stes" if the comparison failed here, 'count' is 3; 'Gulliver' is cbPattern-(4-1)-5 //3:"test" if the comparison failed here, 'count' is 4; 'Gulliver' is cbPattern-(4-1)-4 //4:"est " if the comparison failed here, 'count' is 5; 'Gulliver' is cbPattern-(4-1)-3 //5:"st f" if the comparison failed here, 'count' is 6; 'Gulliver' is cbPattern-(4-1)-2 //6:"t fo" if the comparison failed here, 'count' is 7; 'Gulliver' is cbPattern-(4-1)-1 //7:" fox" if the comparison failed here, 'count' is 8; 'Gulliver' is cbPattern-(4-1) //count = cbPattern-4+1; // Below comparison is UNIdirectional: //while ( count > 0 && *(uint32_t *)(pbPattern+count-1) == *(uint32_t *)(&pbTarget[i]+(count-1)) ) // count = count-4; // count = cbPattern-4+1 = 23-4+1 = 20 // boomshakalakaZZZZZZ[ZZZZ] 20 // boomshakalakaZZ[ZZZZ]ZZZZ 20-4 // boomshakala[kaZZ]ZZZZZZZZ 20-8 = 12 // boomsha[kala]kaZZZZZZZZZZ 20-12 = 8 // boo[msha]kalakaZZZZZZZZZZ 20-16 = 4 // In order to avoid only-left or only-right WCS the memcmp should be done as left-to-right and right-to-left AT THE SAME TIME. // Below comparison is BIdirectional. It pays off when needle is 8+++ long: for (count = cbPattern-4+1; count > 0; count = count-4) { if ( *(uint32_t *)(pbPattern+count-1) != *(uint32_t *)(&pbTarget[i]+(count-1)) ) {break;}; if ( *(uint32_t *)(pbPattern+(cbPattern-4+1)-count) != *(uint32_t *)(&pbTarget[i]+(cbPattern-4+1)-count) ) {count = (cbPattern-4+1)-count +(1); break;} // +(1) because two lookups are implemented as one, also no danger of 'count' being 0 because of the fast check outwith the 'while': if ( *(uint32_t *)&pbTarget[i] == ulHashPattern) } if ( count <= 0 ) return(pbTarget+i); // else { // Checking the order 2 pairs in mismatched DWORD, all the 3: //if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1]] == 0 ) Gulliver = count; // 1 or bigger, as it should //if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1+1]] == 0 ) Gulliver = count+1; // 1 or bigger, as it should //if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1+1+1]] == 0 ) Gulliver = count+1+1; // 1 or bigger, as it should // if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1]] + bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1+1]] + bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1+1+1]] < 3 ) Gulliver = count; // 1 or bigger, as it should, THE MIN(count,count+1,count+1+1) // Above compound 'if' guarantees not that Gulliver > 1, an example: // Needle: fastest tax // Window: ...fastast tax... // After matching ' tax' vs ' tax' and 'fast' vs 'fast' the mismathced DWORD is 'test' vs 'tast': // 'tast' when factorized down to order 2 yields: 'ta','as','st' - all the three when summed give 1+1+1=3 i.e. Gulliver remains 1. // Roughly speaking, this attempt maybe has its place in worst-case scenarios but not in English text and even not in ACGT data, that's why I commented it in original 'Shockeroo'. //if ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+count-1]>>16)+(*(uint32_t *)&pbTarget[i+count-1]&0xFFFF) ) & ( (1<<16)-1 )] == 0 ) Gulliver = count; // 1 or bigger, as it should // Above line is replaced by next one with better hashing: if ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+count-1]>>(16-1))+(*(uint32_t *)&pbTarget[i+count-1]&0xFFFF) ) & ( (1<<16)-1 )] == 0 ) Gulliver = count; // 1 or bigger, as it should // } // Order 4 ] } } } else Gulliver = cbPattern-(2-1)-2; // -2 because we check the 4 rightmost bytes not 2. i = i + Gulliver; //GlobalI++; // Comment it, it is only for stats. } return(NULL); } // if ( cbPattern<=NeedleThreshold2vs4Nonus ) } //if ( cbPattern<4 ) } // Railgun_DecumanusBITified, copyleft 2014-Jan-14, Kaze. // [Latin decumanus var. of decimanus of or belonging to the tenth part or tenth cohort, (by metonymy) large, from decimus: see DECIMAL.] // 1. Esp. of a wave: very large, immense. M17. // 2. Roman History. Of or belonging to the tenth cohort. E19. // decuman gate ~ the main gate of the camp where the tenth cohort was quartered. // /SOED/ // In Roman city planning, a decumanus was an east-west-oriented road in a Roman city, castra (military camp), or colonia. The main decumanus was the Decumanus Maximus, which normally connected the Porta Praetoria (in a military camp, closest to the enemy) to the Porta Decumana (away from the enemy). // This name comes from the fact that the via decumana or decimana (the tenth) separated the Tenth Cohort from the Ninth in the legionary encampment, in the same way as the via quintana separated the Fifth Cohort from the Sixth. // In the middle, or groma, the Decumanus Maximus crosses the perpendicular Cardo Maximus, the primary north-south road that was the usual main street. The Forum is normally located close to this intersection of the Decumanus Maximus and the Cardo Maximus. // /Wikipedia/ // duodecimal // adj. // 1. Of, relating to, or based on the number 12: the duodecimal number system. // 2. Of or relating to twelfths. // n. // A twelfth. // [From Latin duodecimus, twelfth, from duodecim, twelve : duo, two; see dwo- in Indo-European roots + decem, ten; see dek in Indo-European roots.] // /Heritage/ // Caution: For better speed the case 'if (cbPattern==1)' was removed, so Pattern must be longer than 1 char. #define NeedleThreshold2vs4Decumanus 10+9 // Should be bigger than 10 (decimanus, got it). BMH2 works up to this value (inclusive), if bigger then BMH4 takes over. #define _rotl_KAZE(x, n) (((x) << (n)) | ((x) >> (32-(n)))) #define _HASH_Order4_KAZE(x) (( (x>>(16-1))+(x&0xFFFF) ) & ( (1<<16)-1 )) char * Railgun_DecumanusBITified (char * pbTarget, char * pbPattern, uint32_t cbTarget, uint32_t cbPattern) { char * pbTargetMax = pbTarget + cbTarget; register uint32_t ulHashPattern; signed long count; //unsigned char bm_Horspool_Order2[256*256]; // Bitwise soon... unsigned char bm_Horspool_Order2[(256*256)>>3]; uint32_t i, Gulliver; if (cbPattern > cbTarget) return(NULL); if ( cbPattern<4 ) { // SSE2 i.e. 128bit Assembly rules here: // ... pbTarget = pbTarget+cbPattern; ulHashPattern = ( (*(char *)(pbPattern))<<8 ) + *(pbPattern+(cbPattern-1)); if ( cbPattern==3 ) { for ( ;; ) { if ( ulHashPattern == ( (*(char *)(pbTarget-3))<<8 ) + *(pbTarget-1) ) { if ( *(char *)(pbPattern+1) == *(char *)(pbTarget-2) ) return((pbTarget-3)); } if ( (char)(ulHashPattern>>8) != *(pbTarget-2) ) { pbTarget++; if ( (char)(ulHashPattern>>8) != *(pbTarget-2) ) pbTarget++; } pbTarget++; if (pbTarget > pbTargetMax) return(NULL); } } else { } for ( ;; ) { if ( ulHashPattern == ( (*(char *)(pbTarget-2))<<8 ) + *(pbTarget-1) ) return((pbTarget-2)); if ( (char)(ulHashPattern>>8) != *(pbTarget-1) ) pbTarget++; pbTarget++; if (pbTarget > pbTargetMax) return(NULL); } } else { //if ( cbPattern<4 ) if ( cbPattern<=NeedleThreshold2vs4Decumanus ) { // BMH order 2, needle should be >=4: ulHashPattern = *(uint32_t *)(pbPattern); // First four bytes //for (i=0; i < 256*256; i++) {bm_Horspool_Order2[i]=0;} for (i=0; i < (256*256)>>3; i++) {bm_Horspool_Order2[i]=0;} //for (i=0; i < cbPattern-1; i++) bm_Horspool_Order2[*(unsigned short *)(pbPattern+i)]=1; for (i=0; i < cbPattern-2+1; i++) bm_Horspool_Order2[(*(unsigned short *)(pbPattern+i))>>3]= bm_Horspool_Order2[(*(unsigned short *)(pbPattern+i))>>3] | (1<<((*(unsigned short *)(pbPattern+i))&0x7)); i=0; while (i <= cbTarget-cbPattern) { Gulliver = 1; // 'Gulliver' is the skip //if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+cbPattern-1-1]] != 0 ) { if ( ( bm_Horspool_Order2[(*(unsigned short *)&pbTarget[i+cbPattern-1-1])>>3] & (1<<((*(unsigned short *)&pbTarget[i+cbPattern-1-1])&0x7)) ) != 0 ) { //if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+cbPattern-1-1-2]] == 0 ) Gulliver = cbPattern-(2-1)-2; else { if ( ( bm_Horspool_Order2[(*(unsigned short *)&pbTarget[i+cbPattern-1-1-2])>>3] & (1<<((*(unsigned short *)&pbTarget[i+cbPattern-1-1-2])&0x7)) ) == 0 ) Gulliver = cbPattern-(2-1)-2; else { if ( *(uint32_t *)&pbTarget[i] == ulHashPattern) { // This fast check ensures not missing a match (for remainder) when going under 0 in loop below: count = cbPattern-4+1; while ( count > 0 && *(uint32_t *)(pbPattern+count-1) == *(uint32_t *)(&pbTarget[i]+(count-1)) ) count = count-4; if ( count <= 0 ) return(pbTarget+i); } } } else Gulliver = cbPattern-(2-1); i = i + Gulliver; //GlobalI++; // Comment it, it is only for stats. } return(NULL); } else { // if ( cbPattern<=NeedleThreshold2vs4Decumanus ) // BMH pseudo-order 4, needle should be >=8+2: ulHashPattern = *(uint32_t *)(pbPattern); // First four bytes //for (i=0; i < 256*256; i++) {bm_Horspool_Order2[i]=0;} for (i=0; i < (256*256)>>3; i++) {bm_Horspool_Order2[i]=0;} // In line below we "hash" 4bytes to 2bytes i.e. 16bit table, how to compute TOTAL number of BBs, 'cbPattern - Order + 1' is the number of BBs for text 'cbPattern' bytes long, for example, for cbPattern=11 'fastest fox' and Order=4 we have BBs = 11-4+1=8: //"fast" //"aste" //"stes" //"test" //"est " //"st f" //"t fo" //" fox" //for (i=0; i < cbPattern-4+1; i++) bm_Horspool_Order2[( *(unsigned short *)(pbPattern+i+0) + *(unsigned short *)(pbPattern+i+2) ) & ( (1<<16)-1 )]=1; //for (i=0; i < cbPattern-4+1; i++) bm_Horspool_Order2[( (*(uint32_t *)(pbPattern+i+0)>>16)+(*(uint32_t *)(pbPattern+i+0)&0xFFFF) ) & ( (1<<16)-1 )]=1; // Above line is replaced by next one with better hashing: //for (i=0; i < cbPattern-4+1; i++) bm_Horspool_Order2[( (*(uint32_t *)(pbPattern+i+0)>>(16-1))+(*(uint32_t *)(pbPattern+i+0)&0xFFFF) ) & ( (1<<16)-1 )]=1; for (i=0; i < cbPattern-4+1; i++) bm_Horspool_Order2[_HASH_Order4_KAZE(*(uint32_t *)(pbPattern+i+0))>>3]= bm_Horspool_Order2[(_HASH_Order4_KAZE(*(uint32_t *)(pbPattern+i+0)))>>3] | (1<<((_HASH_Order4_KAZE(*(uint32_t *)(pbPattern+i+0)))&0x7)); i=0; while (i <= cbTarget-cbPattern) { Gulliver = 1; //if ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2]&0xFFFF) ) & ( (1<<16)-1 )] != 0 ) { // DWORD #1 // Above line is replaced by next one with better hashing: //if ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2]>>(16-1))+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2]&0xFFFF) ) & ( (1<<16)-1 )] != 0 ) { // DWORD #1 if ( ( bm_Horspool_Order2[(_HASH_Order4_KAZE(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2]))>>3] & (1<<((_HASH_Order4_KAZE(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2]))&0x7)) ) != 0 ) { // DWORD #1 //if ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) ) & ( (1<<16)-1 )] == 0 ) Gulliver = cbPattern-(2-1)-2-4; else { // Above line is replaced in order to strengthen the skip by checking the middle DWORD,if the two DWORDs are 'ab' and 'cd' i.e. [2x][2a][2b][2c][2d] then the middle DWORD is 'bc'. // The respective offsets (backwards) are: -10/-8/-6/-4 for 'xa'/'ab'/'bc'/'cd'. //if ( ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) ) & ( (1<<16)-1 )] ) < 3 ) Gulliver = cbPattern-(2-1)-2-4-2; else { // Above line is replaced by next one with better hashing: // When using (16-1) right shifting instead of 16 we will have two different pairs (if they are equal), the highest bit being lost do the job especialy for ASCII texts with no symbols in range 128-255. // Example for genomesque pair TT+TT being shifted by (16-1): // T = 01010100 // TT = 01010100 01010100 // TTTT = 01010100 01010100 01010100 01010100 // TTTT>>16 = 00000000 00000000 01010100 01010100 // TTTT>>(16-1) = 00000000 00000000 10101000 10101000 <--- Due to the left shift by 1, the 8th bits of 1st and 2nd bytes are populated - usually they are 0 for English texts & 'ACGT' data. //if ( ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]>>(16-1))+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]>>(16-1))+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]>>(16-1))+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) ) & ( (1<<16)-1 )] ) < 3 ) Gulliver = cbPattern-(2-1)-2-4-2; else { if ( \ ( bm_Horspool_Order2[(_HASH_Order4_KAZE(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]))>>3] & (1<<((_HASH_Order4_KAZE(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]))&0x7)) ) == 0 || \ ( bm_Horspool_Order2[(_HASH_Order4_KAZE(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]))>>3] & (1<<((_HASH_Order4_KAZE(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]))&0x7)) ) == 0 || \ ( bm_Horspool_Order2[(_HASH_Order4_KAZE(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]))>>3] & (1<<((_HASH_Order4_KAZE(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]))&0x7)) ) == 0 ) Gulliver = cbPattern-(2-1)-2-4-2; else { // Note: Not unbranched as in BYTEwise (above) line. // Above line is not optimized (several a SHR are used), we have 5 non-overlapping WORDs, or 3 overlapping WORDs, within 4 overlapping DWORDs so: // [2x][2a][2b][2c][2d] // DWORD #4 // [2a] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]>>16) = !SHR to be avoided! <-- // [2x] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]&0xFFFF) = | // DWORD #3 | // [2b] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]>>16) = !SHR to be avoided! |<-- // [2a] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) = ------------------------ | // DWORD #2 | // [2c] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]>>16) = !SHR to be avoided! |<-- // [2b] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) = --------------------------- | // DWORD #1 | // [2d] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]>>16) = | // [2c] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]&0xFFFF) = ------------------------------ // // So in order to remove 3 SHR instructions the equal extractions are: // DWORD #4 // [2a] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) = !SHR to be avoided! <-- // [2x] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]&0xFFFF) = | // DWORD #3 | // [2b] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) = !SHR to be avoided! |<-- // [2a] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) = ------------------------ | // DWORD #2 | // [2c] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]&0xFFFF) = !SHR to be avoided! |<-- // [2b] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) = --------------------------- | // DWORD #1 | // [2d] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]>>16) = | // [2c] (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]&0xFFFF) = ------------------------------ //if ( ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-6]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-0]&0xFFFF)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-2]&0xFFFF) ) & ( (1<<16)-1 )] ) < 3 ) Gulliver = cbPattern-(2-1)-2-6; else { // Since the above Decumanus mumbo-jumbo (3 overlapping lookups vs 2 non-overlapping lookups) is not fast enough we go DuoDecumanus or 3x4: // [2y][2x][2a][2b][2c][2d] // DWORD #3 // DWORD #2 // DWORD #1 //if ( ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-4]&0xFFFF) ) & ( (1<<16)-1 )] ) + ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-8]>>16)+(*(uint32_t *)&pbTarget[i+cbPattern-1-1-2-8]&0xFFFF) ) & ( (1<<16)-1 )] ) < 2 ) Gulliver = cbPattern-(2-1)-2-8; else { if ( *(uint32_t *)&pbTarget[i] == ulHashPattern) { // Order 4 [ // Let's try something "outrageous" like comparing with[out] overlap BBs 4bytes long instead of 1 byte back-to-back: // Inhere we are using order 4, 'cbPattern - Order + 1' is the number of BBs for text 'cbPattern' bytes long, for example, for cbPattern=11 'fastest fox' and Order=4 we have BBs = 11-4+1=8: //0:"fast" if the comparison failed here, 'count' is 1; 'Gulliver' is cbPattern-(4-1)-7 //1:"aste" if the comparison failed here, 'count' is 2; 'Gulliver' is cbPattern-(4-1)-6 //2:"stes" if the comparison failed here, 'count' is 3; 'Gulliver' is cbPattern-(4-1)-5 //3:"test" if the comparison failed here, 'count' is 4; 'Gulliver' is cbPattern-(4-1)-4 //4:"est " if the comparison failed here, 'count' is 5; 'Gulliver' is cbPattern-(4-1)-3 //5:"st f" if the comparison failed here, 'count' is 6; 'Gulliver' is cbPattern-(4-1)-2 //6:"t fo" if the comparison failed here, 'count' is 7; 'Gulliver' is cbPattern-(4-1)-1 //7:" fox" if the comparison failed here, 'count' is 8; 'Gulliver' is cbPattern-(4-1) count = cbPattern-4+1; while ( count > 0 && *(uint32_t *)(pbPattern+count-1) == *(uint32_t *)(&pbTarget[i]+(count-1)) ) count = count-4; if ( count <= 0 ) return(pbTarget+i); else { // Checking the order 2 pairs in mismatched DWORD, all the 3: //if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1]] == 0 ) Gulliver = count; // 1 or bigger, as it should //if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1+1]] == 0 ) Gulliver = count+1; // 1 or bigger, as it should //if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1+1+1]] == 0 ) Gulliver = count+1+1; // 1 or bigger, as it should // if ( bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1]] + bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1+1]] + bm_Horspool_Order2[*(unsigned short *)&pbTarget[i+count-1+1+1]] < 3 ) Gulliver = count; // 1 or bigger, as it should, THE MIN(count,count+1,count+1+1) // Above compound 'if' guarantees not that Gulliver > 1, an example: // Needle: fastest tax // Window: ...fastast tax... // After matching ' tax' vs ' tax' and 'fast' vs 'fast' the mismathced DWORD is 'test' vs 'tast': // 'tast' when factorized down to order 2 yields: 'ta','as','st' - all the three when summed give 1+1+1=3 i.e. Gulliver remains 1. // Roughly speaking, this attempt maybe has its place in worst-case scenarios but not in English text and even not in ACGT data, that's why I commented it in original 'Shockeroo'. //if ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+count-1]>>16)+(*(uint32_t *)&pbTarget[i+count-1]&0xFFFF) ) & ( (1<<16)-1 )] == 0 ) Gulliver = count; // 1 or bigger, as it should // Above line is replaced by next one with better hashing: //if ( bm_Horspool_Order2[( (*(uint32_t *)&pbTarget[i+count-1]>>(16-1))+(*(uint32_t *)&pbTarget[i+count-1]&0xFFFF) ) & ( (1<<16)-1 )] == 0 ) Gulliver = count; // 1 or bigger, as it should if ( ( bm_Horspool_Order2[(_HASH_Order4_KAZE(*(uint32_t *)&pbTarget[i+count-1]))>>3] & (1<<((_HASH_Order4_KAZE(*(uint32_t *)&pbTarget[i+count-1]))&0x7)) ) == 0 ) Gulliver = count; // 1 or bigger, as it should } // Order 4 ] } } } else Gulliver = cbPattern-(2-1)-2; // -2 because we check the 4 rightmost bytes not 2. i = i + Gulliver; //GlobalI++; // Comment it, it is only for stats. } return(NULL); } // if ( cbPattern<=NeedleThreshold2vs4Decumanus ) } //if ( cbPattern<4 ) } ```

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