projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 6b525888 SJ |
1 | #include <stdio.h> |
| 2 | #include <ctype.h> | |
| 3 | ||
| 4 | #ifndef unix | |
| 5 | #define SHIFT 5 | |
| 6 | #define TABSIZE (int)(400000/(1<<SHIFT)) | |
| 7 | int *tab; /*honeywell loader deficiency*/ | |
| 8 | #else | |
| 9 | #define Tolower(c) (isupper(c)?tolower(c):c) /* ugh!!! */ | |
| 10 | #define SHIFT 4 | |
| 11 | #define TABSIZE 25000 /*(int)(400000/(1<<shift))--pdp11 compiler deficiency*/ | |
| 12 | short tab[TABSIZE]; | |
| 13 | #endif | |
| 14 | long p[] = { | |
| 15 | 399871, | |
| 16 | 399887, | |
| 17 | 399899, | |
| 18 | 399911, | |
| 19 | 399913, | |
| 20 | 399937, | |
| 21 | 399941, | |
| 22 | 399953, | |
| 23 | 399979, | |
| 24 | 399983, | |
| 25 | 399989, | |
| 26 | }; | |
| 27 | #define NP (sizeof(p)/sizeof(p[0])) | |
| 28 | #define NW 30 | |
| 29 | ||
| 30 | /* | |
| 31 | * Hash table for spelling checker has n bits. | |
| 32 | * Each word w is hashed by k different (modular) hash functions, hi. | |
| 33 | * The bits hi(w), i=1..k, are set for words in the dictionary. | |
| 34 | * Assuming independence, the probability that no word of a d-word | |
| 35 | * dictionary sets a particular bit is given by the Poisson formula | |
| 36 | * P = exp(-y)*y**0/0!, where y=d*k/n. | |
| 37 | * The probability that a random string is recognized as a word is then | |
| 38 | * (1-P)**k. For given n and d this is minimum when y=log(2), P=1/2, | |
| 39 | * whence one finds, for example, that a 25000-word dictionary in a | |
| 40 | * 400000-bit table works best with k=11. | |
| 41 | */ | |
| 42 | ||
| 43 | long pow2[NP][NW]; | |
| 44 | ||
| 45 | prime(argc, argv) register char **argv; | |
| 46 | { | |
| 47 | int i, j; | |
| 48 | long h; | |
| 49 | register long *lp; | |
| 50 | ||
| 51 | #ifndef unix | |
| 52 | if ((tab = (int *)calloc(sizeof(*tab), TABSIZE)) == NULL) | |
| 53 | return(0); | |
| 54 | #endif | |
| 55 | if (argc > 1) { | |
| 56 | FILE *f; | |
| 57 | if ((f = fopen(argv[1], "ri")) == NULL) | |
| 58 | return(0); | |
| 59 | if (fread((char *)tab, sizeof(*tab), TABSIZE, f) != TABSIZE) | |
| 60 | return(0); | |
| 61 | fclose(f); | |
| 62 | } | |
| 63 | for (i=0; i<NP; i++) { | |
| 64 | h = *(lp = pow2[i]) = 1<<14; | |
| 65 | for (j=1; j<NW; j++) | |
| 66 | h = *++lp = (h<<7) % p[i]; | |
| 67 | } | |
| 68 | return(1); | |
| 69 | } | |
| 70 | ||
| 71 | #define get(h) (tab[h>>SHIFT]&(1<<((int)h&((1<<SHIFT)-1)))) | |
| 72 | #define set(h) tab[h>>SHIFT] |= 1<<((int)h&((1<<SHIFT)-1)) |