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(svn r1951) Introduced SeedModChance() (which is like SeedChance() but uses simple modulo instead of bitshifting and multiplication), explained why does it work better, used it in MakeCzechTownName() and added a TODO note about possibly using it in the other town name generators too.

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This commit is contained in:
pasky 2005-03-06 23:21:57 +00:00
parent 6902a8b294
commit 028ef2b5b5
1 changed files with 22 additions and 8 deletions
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30
namegen.c
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@ -9,6 +9,20 @@ static inline uint32 SeedChance(int shift_by, int max, uint32 seed)
return ((uint16)(seed >> shift_by) * max) >> 16; return ((uint16)(seed >> shift_by) * max) >> 16;
} }
static inline uint32 SeedModChance(int shift_by, int max, uint32 seed)
{
/* This actually gives *MUCH* more even distribution of the values
* than SeedChance(), which is absolutely horrible in that. If
* you do not believe me, try with i.e. the Czech town names,
* compare the words (nicely visible on prefixes) generated by
* SeedChance() and SeedModChance(). Do not get dicouraged by the
* never-use-modulo myths, which hold true only for the linear
* congruential generators (and Random() isn't such a generator).
* --pasky */
// TODO: Perhaps we should use it for all the name generators? --pasky
return (seed >> shift_by) % max;
}
static inline int32 SeedChanceBias(int shift_by, int max, uint32 seed, int bias) static inline int32 SeedChanceBias(int shift_by, int max, uint32 seed, int bias)
{ {
return SeedChance(shift_by, max + bias, seed) - bias; return SeedChance(shift_by, max + bias, seed) - bias;
@ -330,22 +344,22 @@ static byte MakeCzechTownName(char *buf, uint32 seed)
enum CzechAllow allow; enum CzechAllow allow;
// 1:3 chance to use a real name. // 1:3 chance to use a real name.
if (SeedChance(0, 4, seed) == 0) { if (SeedModChance(0, 4, seed) == 0) {
strcpy(buf, name_czech_real[SeedChance(1, lengthof(name_czech_real), seed)]); strcpy(buf, name_czech_real[SeedModChance(4, lengthof(name_czech_real), seed)]);
return 0; return 0;
} }
// NUL terminates the string for strcat() // NUL terminates the string for strcat()
strcpy(buf, ""); strcpy(buf, "");
prob_tails = SeedChance(2, 32, seed); prob_tails = SeedModChance(2, 32, seed);
do_prefix = prob_tails < 12; do_prefix = prob_tails < 12;
do_suffix = prob_tails > 11 && prob_tails < 17; do_suffix = prob_tails > 11 && prob_tails < 17;
if (do_prefix) prefix = SeedChance(5, lengthof(name_czech_adj), seed); if (do_prefix) prefix = SeedModChance(5, lengthof(name_czech_adj) * 12, seed) / 12;
if (do_suffix) suffix = SeedChance(7, lengthof(name_czech_suffix), seed); if (do_suffix) suffix = SeedModChance(7, lengthof(name_czech_suffix), seed);
// 3:1 chance 3:1 to use dynamic substantive // 3:1 chance 3:1 to use dynamic substantive
stem = SeedChance(9, lengthof(name_czech_subst_full) stem = SeedModChance(9, lengthof(name_czech_subst_full)
+ 3 * lengthof(name_czech_subst_stem), + 3 * lengthof(name_czech_subst_stem),
seed); seed);
if (stem < (int) lengthof(name_czech_subst_full)) { if (stem < (int) lengthof(name_czech_subst_full)) {
@ -369,7 +383,7 @@ static byte MakeCzechTownName(char *buf, uint32 seed)
allow = name_czech_subst_stem[stem].allow; allow = name_czech_subst_stem[stem].allow;
// Load the postfix (1:1 chance that a postfix will be inserted) // Load the postfix (1:1 chance that a postfix will be inserted)
postfix = SeedChance(14, lengthof(name_czech_subst_postfix) * 2, seed); postfix = SeedModChance(14, lengthof(name_czech_subst_postfix) * 2, seed);
if (choose & CZC_POSTFIX) { if (choose & CZC_POSTFIX) {
// Always get a real postfix. // Always get a real postfix.
@ -415,7 +429,7 @@ static byte MakeCzechTownName(char *buf, uint32 seed)
assert(i > 0); assert(i > 0);
// Load the ending // Load the ending
ending = map[SeedChance(16, i, seed)]; ending = map[SeedModChance(16, i, seed)];
// Override possible CZG_*FREE; this must be a real gender, // Override possible CZG_*FREE; this must be a real gender,
// otherwise we get overflow when modifying the adjectivum. // otherwise we get overflow when modifying the adjectivum.
gender = name_czech_subst_ending[ending].gender; gender = name_czech_subst_ending[ending].gender;