diff options
Diffstat (limited to 'generator/pgmnoise.c')
| -rw-r--r-- | generator/pgmnoise.c | 80 |
1 files changed, 50 insertions, 30 deletions
diff --git a/generator/pgmnoise.c b/generator/pgmnoise.c index e3e4eca6..f5f48ff3 100644 --- a/generator/pgmnoise.c +++ b/generator/pgmnoise.c @@ -7,12 +7,12 @@ #include "pm_c_util.h" #include "mallocvar.h" #include "nstring.h" +#include "rand.h" #include "shhopt.h" #include "pgm.h" - -struct cmdlineInfo { +struct CmdlineInfo { /* All the information the user supplied in the command line, in a form easy for the program to use. */ @@ -21,13 +21,15 @@ struct cmdlineInfo { unsigned int maxval; unsigned int randomseed; unsigned int randomseedSpec; + unsigned int verbose; }; static void -parseCommandLine(int argc, const char ** const argv, - struct cmdlineInfo * const cmdlineP) { +parseCommandLine(int argc, + const char ** const argv, + struct CmdlineInfo * const cmdlineP) { /*---------------------------------------------------------------------------- Note that the file spec array we return is stored in the storage that was passed to us as the argv array. @@ -46,6 +48,8 @@ parseCommandLine(int argc, const char ** const argv, &cmdlineP->randomseedSpec, 0); OPTENT3(0, "maxval", OPT_UINT, &cmdlineP->maxval, &maxvalSpec, 0); + OPTENT3(0, "verbose", OPT_FLAG, NULL, + &cmdlineP->verbose, 0); opt.opt_table = option_def; opt.short_allowed = FALSE; /* We have no short (old-fashioned) options */ @@ -57,7 +61,7 @@ parseCommandLine(int argc, const char ** const argv, if (maxvalSpec) { if (cmdlineP->maxval > PGM_OVERALLMAXVAL) - pm_error("Maxval too large: %u. Maximu is %u", + pm_error("Maxval too large: %u. Maximum is %u", cmdlineP->maxval, PGM_OVERALLMAXVAL); else if (cmdlineP->maxval == 0) pm_error("Maxval must not be zero"); @@ -95,15 +99,21 @@ parseCommandLine(int argc, const char ** const argv, static unsigned int -randPool(unsigned int const digits) { +randPool(unsigned int const digits, + bool const verbose, + struct pm_randSt * const randStP) { /*---------------------------------------------------------------------------- Draw 'digits' bits from pool of random bits. If the number of random bits - in pool is insufficient, call rand() and add 31 bits to it. + in pool is insufficient, call pm_rand() and add N bits to it. + + N is 31 or 32. In raw mode we set this value to 32 regardless of the + actual number of available bits. If insufficient, the MSB will be + set to zero. 'digits' must be at most 16. - We assume that each call to rand() generates 31 bits, or RAND_MAX == - 2147483647. + We assume that each call to pm_rand() generates 31 or 32 bits, + or randStP->max == 2147483647 or 4294967294. The underlying logic is flexible and endian-free. The above conditions can be relaxed. @@ -112,21 +122,24 @@ randPool(unsigned int const digits) { static unsigned int len=0; /* number of valid bits in pool */ unsigned int const mask = (1 << digits) - 1; - + unsigned int const randbits = (randStP->max == 2147483647) ? 31 : 32; unsigned int retval; - assert(RAND_MAX == 2147483647 && digits <= 16); + assert(randStP->max == 2147483647 || randStP->max == 4294967294); + assert(digits <= 16); retval = hold; /* initial value */ if (len > digits) { /* Enough bits in hold to satisfy request */ hold >>= digits; len -= digits; - } else { /* Load another 31 bits into hold */ - hold = rand(); + } else { /* Load another 31 or 32 bits into hold */ + hold = pm_rand(randStP); + if (verbose) + pm_message("pm_rand(): %08lX", hold); retval |= (hold << len); hold >>= (digits - len); - len = 31 - digits + len; + len = randbits - digits + len; } return (retval & mask); } @@ -134,19 +147,23 @@ randPool(unsigned int const digits) { static void -pgmnoise(FILE * const ofP, - unsigned int const cols, - unsigned int const rows, - gray const maxval) { - - bool const usingPool = !(RAND_MAX==2147483647 && (maxval & (maxval+1))); +pgmnoise(FILE * const ofP, + unsigned int const cols, + unsigned int const rows, + gray const maxval, + bool const verbose, + struct pm_randSt * const randStP) { + + bool const usingPool = + !( (randStP->max==2147483647UL || randStP->max==4294967294UL) + && (maxval & (maxval+1)) ); unsigned int const bitLen = pm_maxvaltobits(maxval); unsigned int row; gray * destrow; /* If maxval is 2^n-1, we draw exactly n bits from the pool. - Otherwise call rand() and determine gray value by modulo. + Otherwise call pm_rand() and determine gray value by modulo. In the latter case, there is a minuscule skew toward 0 (=black) because smaller numbers are produced more frequently by modulo. @@ -155,7 +172,7 @@ pgmnoise(FILE * const ofP, To illustrate the point, consider converting the outcome of one roll of a fair, six-sided die to 5 values (0 to 4) by N % 5. The - probability for values 1, 2, 3, 4 are 1/6, but 0 alone is 2/6. + probability for values 1, 2, 3, 4 is 1/6, but 0 alone is 2/6. Average is 10/6 or 1.6667, compared to 2.0 from an ideal generator which produces exactly 5 values. With two dice average improves to 70/36 or 1.9444. @@ -172,12 +189,11 @@ pgmnoise(FILE * const ofP, if (usingPool) { unsigned int col; for (col = 0; col < cols; ++col) - destrow[col] = randPool(bitLen); - } - else { + destrow[col] = randPool(bitLen, verbose, randStP); + } else { unsigned int col; for (col = 0; col < cols; ++col) - destrow[col] = rand() % (maxval + 1); + destrow[col] = pm_rand(randStP) % (maxval + 1); } pgm_writepgmrow(ofP, destrow, cols, maxval, 0); } @@ -191,18 +207,22 @@ int main(int argc, const char * argv[]) { - struct cmdlineInfo cmdline; + struct CmdlineInfo cmdline; + struct pm_randSt randSt; pm_proginit(&argc, argv); parseCommandLine(argc, argv, &cmdline); - srand(cmdline.randomseedSpec ? cmdline.randomseed : pm_randseed()); + pm_randinit(&randSt); + pm_srand2(&randSt, cmdline.randomseedSpec, cmdline.randomseed); + + pgmnoise(stdout, cmdline.width, cmdline.height, cmdline.maxval, + cmdline.verbose, &randSt); - pgmnoise(stdout, cmdline.width, cmdline.height, cmdline.maxval); + pm_randterm(&randSt); return 0; } - |