#define m_initsgrp(mtmp, x, y, mmf) m_initgrp(mtmp, x, y, 3, mmf)
#define m_initlgrp(mtmp, x, y, mmf) m_initgrp(mtmp, x, y, 10, mmf)
-#define toostrong(monindx, lev) (mons[monindx].difficulty > lev)
-#define tooweak(monindx, lev) (mons[monindx].difficulty < lev)
boolean
is_home_elemental(ptr)
makeplural(mons[mndx].mname));
}
g.mvitals[mndx].mvflags |= G_EXTINCT;
- reset_rndmonst(mndx);
}
return result;
}
rndmonst()
{
register struct permonst *ptr;
- register int mndx, ct;
+ register int mndx;
+ int weight, totalweight, selected_mndx, zlevel, minmlev, maxmlev;
+ boolean elemlevel, upper;
if (u.uz.dnum == quest_dnum && rn2(7) && (ptr = qt_montype()) != 0)
return ptr;
- if (g.rndmonst_state.choice_count < 0) { /* need to recalculate */
- int zlevel, minmlev, maxmlev;
- boolean elemlevel;
- boolean upper;
+ zlevel = level_difficulty();
+ minmlev = monmin_difficulty(zlevel);
+ maxmlev = monmax_difficulty(zlevel);
+ upper = Is_rogue_level(&u.uz); /* prefer uppercase only on rogue level */
+ elemlevel = In_endgame(&u.uz) && !Is_astralevel(&u.uz); /* elmntl plane */
- g.rndmonst_state.choice_count = 0;
- /* look for first common monster */
- for (mndx = LOW_PM; mndx < SPECIAL_PM; mndx++) {
- if (!uncommon(mndx))
- break;
- g.rndmonst_state.mchoices[mndx] = 0;
- }
- if (mndx == SPECIAL_PM) {
- /* evidently they've all been exterminated */
- debugpline0("rndmonst: no common mons!");
- return (struct permonst *) 0;
- } /* else `mndx' now ready for use below */
- zlevel = level_difficulty();
- /* determine the level of the weakest monster to make. */
- minmlev = zlevel / 6;
- /* determine the level of the strongest monster to make. */
- maxmlev = (zlevel + u.ulevel) / 2;
- upper = Is_rogue_level(&u.uz);
- elemlevel = In_endgame(&u.uz) && !Is_astralevel(&u.uz);
+ /* amount processed so far */
+ totalweight = 0;
+ selected_mndx = NON_PM;
+
+ for (mndx = LOW_PM; mndx < SPECIAL_PM; ++mndx) {
+ ptr = &mons[mndx];
+
+ if (montooweak(mndx, minmlev) || montoostrong(mndx, maxmlev))
+ continue;
+ if (upper && !isupper((uchar) def_monsyms[(int) ptr->mlet].sym))
+ continue;
+ if (elemlevel && wrong_elem_type(ptr))
+ continue;
+ if (uncommon(mndx))
+ continue;
+ if (Inhell && (ptr->geno & G_NOHELL))
+ continue;
/*
- * Find out how many monsters exist in the range we have selected.
+ * Weighted reservoir sampling: select ptr with a
+ * (ptr weight)/(total of all weights so far including ptr's)
+ * probability. For example, if the previous total is 10, and
+ * this is now looking at acid blobs with a frequency of 2, it
+ * has a 2/12 chance of abandoning ptr's previous value in favor
+ * of acid blobs, and 10/12 chance of keeping whatever it was.
+ *
+ * This does not bias results towards either the earlier or the
+ * later monsters: the smaller pool and better odds from being
+ * earlier are exactly canceled out by having more monsters to
+ * potentially steal its spot.
*/
- for ( ; mndx < SPECIAL_PM; mndx++) { /* (`mndx' initialized above) */
- ptr = &mons[mndx];
- g.rndmonst_state.mchoices[mndx] = 0;
- if (tooweak(mndx, minmlev) || toostrong(mndx, maxmlev))
- continue;
- if (upper && !isupper((uchar) def_monsyms[(int) ptr->mlet].sym))
- continue;
- if (elemlevel && wrong_elem_type(ptr))
- continue;
- if (uncommon(mndx))
- continue;
- if (Inhell && (ptr->geno & G_NOHELL))
- continue;
- ct = (int) (ptr->geno & G_FREQ) + align_shift(ptr);
- if (ct < 0 || ct > 127)
- panic("rndmonst: bad count [#%d: %d]", mndx, ct);
- g.rndmonst_state.choice_count += ct;
- g.rndmonst_state.mchoices[mndx] = (char) ct;
+ weight = (int) (ptr->geno & G_FREQ) + align_shift(ptr);
+ if (weight < 0 || weight > 127) {
+ impossible("bad weight in rndmonst for mndx %d", mndx);
+ weight = 0;
+ }
+ /* was unconditional, but if weight==0, rn2() < 0 will always fail;
+ also need to avoid rn2(0) if totalweight is still 0 so far */
+ if (weight > 0) {
+ totalweight += weight; /* totalweight now guaranteed to be > 0 */
+ if (rn2(totalweight) < weight)
+ selected_mndx = mndx;
}
- /*
- * Possible modification: if choice_count is "too low",
- * expand minmlev..maxmlev range and try again.
- */
- } /* choice_count+mchoices[] recalc */
-
- if (g.rndmonst_state.choice_count <= 0) {
- /* maybe no common mons left, or all are too weak or too strong */
- debugpline1("rndmonst: choice_count=%d", g.rndmonst_state.choice_count);
- return (struct permonst *) 0;
}
-
/*
- * Now, select a monster at random.
+ * Possible modification: if totalweight is "too low" or nothing
+ * viable was picked, expand minmlev..maxmlev range and try again.
*/
- ct = rnd(g.rndmonst_state.choice_count);
- for (mndx = LOW_PM; mndx < SPECIAL_PM; mndx++)
- if ((ct -= (int) g.rndmonst_state.mchoices[mndx]) <= 0)
- break;
-
- if (mndx == SPECIAL_PM || uncommon(mndx)) { /* shouldn't happen */
- impossible("rndmonst: bad `mndx' [#%d]", mndx);
+ if (selected_mndx == NON_PM || uncommon(selected_mndx)) {
+ /* maybe no common monsters left, or all are too weak or too strong */
+ if (selected_mndx != NON_PM)
+ debugpline1("rndmonst returning Null [uncommon 'mndx'=#%d]",
+ selected_mndx);
return (struct permonst *) 0;
}
- return &mons[mndx];
-}
-
-/* called when you change level (experience or dungeon depth) or when
- monster species can no longer be created (genocide or extinction) */
-void
-reset_rndmonst(mndx)
-int mndx; /* particular species that can no longer be created */
-{
- /* cached selection info is out of date */
- if (mndx == NON_PM) {
- g.rndmonst_state.choice_count = -1; /* full recalc needed */
- } else if (mndx < SPECIAL_PM) {
- g.rndmonst_state.choice_count -= g.rndmonst_state.mchoices[mndx];
- g.rndmonst_state.mchoices[mndx] = 0;
- } /* note: safe to ignore extinction of unique monsters */
+ return &mons[selected_mndx];
}
/* decide whether it's ok to generate a candidate monster by mkclass() */
(or lower) difficulty as preceding candidate (non-zero
'num' implies last > first so mons[last-1] is safe);
sometimes accept it even if high difficulty */
- if (num && toostrong(last, maxmlev)
+ if (num && montoostrong(last, maxmlev)
&& mons[last].difficulty > mons[last - 1].difficulty
&& rn2(2))
break;
projects / nethack / commitdiff