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* array.c (rb_ary_sample): performance improvement for huge array.

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git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@18719 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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nobu 2008-08-20 07:40:03 +00:00
parent 6523eee836
commit ee5c9fb983
2 changed files with 58 additions and 18 deletions
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ChangeLog
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@ -1,3 +1,7 @@
Wed Aug 20 16:39:59 2008 Nobuyoshi Nakada <nobu@ruby-lang.org>
* array.c (rb_ary_sample): performance improvement for huge array.
Wed Aug 20 12:28:31 2008 Nobuyoshi Nakada <nobu@ruby-lang.org> Wed Aug 20 12:28:31 2008 Nobuyoshi Nakada <nobu@ruby-lang.org>
* array.c (rb_ary_sample): get rid of infinite loop. #455 * array.c (rb_ary_sample): get rid of infinite loop. #455

72
array.c
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@ -3022,35 +3022,71 @@ rb_ary_shuffle(VALUE ary)
static VALUE static VALUE
rb_ary_sample(int argc, VALUE *argv, VALUE ary) rb_ary_sample(int argc, VALUE *argv, VALUE ary)
{ {
VALUE nv, result; VALUE nv, result, *ptr;
int n, len, i, j; long n, len, i, j, k, idx[10];
len = RARRAY_LEN(ary); len = RARRAY_LEN(ary);
if (argc == 0) { if (argc == 0) {
if (len == 0) return Qnil; if (len == 0) return Qnil;
i = rb_genrand_real()*len; i = len == 1 ? 0 : rb_genrand_real()*len;
return RARRAY_PTR(ary)[i]; return RARRAY_PTR(ary)[i];
} }
rb_scan_args(argc, argv, "1", &nv); rb_scan_args(argc, argv, "1", &nv);
n = NUM2INT(nv); n = NUM2LONG(nv);
ptr = RARRAY_PTR(ary);
len = RARRAY_LEN(ary);
if (n > len) n = len; if (n > len) n = len;
if (n == 0) return rb_ary_new2(0); switch (n) {
result = rb_ary_new2(n); case 0: return rb_ary_new2(0);
for (i=0; i<n; i++) { case 1:
retry: return rb_ary_new4(1, &ptr[(long)(rb_genrand_real()*len)]);
j = rb_genrand_real()*len; case 2:
nv = LONG2NUM(j); i = rb_genrand_real()*len;
for (j=0; j<i; j++) { j = rb_genrand_real()*(len-1);
if (RARRAY_PTR(result)[j] == nv) if (j == i) j++;
goto retry; return rb_ary_new3(2, ptr[i], ptr[j]);
case 3:
i = rb_genrand_real()*len;
j = rb_genrand_real()*(len-1);
k = rb_genrand_real()*(len-2);
if (j == i) j++;
if ((k == i) ? (++k == j) : (k == j) ? (++k == i): 0) ++k;
return rb_ary_new3(3, ptr[i], ptr[j], ptr[k]);
}
if (n < sizeof(idx)/sizeof(idx[0])) {
idx[0] = rb_genrand_real()*len;
for (i=1; i<n; i++) {
long p = i;
k = rb_genrand_real()*--len;
retry:
j = 0;
do {
if (idx[j] == k) {
++k;
if (p < j) goto retry;
}
else if (idx[j] > k) {
if (p > j) p = j;
}
} while (++j < i);
idx[i] = k;
}
result = rb_ary_new2(n);
for (i=0; i<n; i++) {
RARRAY_PTR(result)[i] = RARRAY_PTR(ary)[idx[i]];
} }
RARRAY_PTR(result)[i] = nv;
ARY_SET_LEN(result, i+1);
} }
for (i=0; i<n; i++) { else {
nv = RARRAY_PTR(result)[i]; result = rb_ary_new4(len, ptr);
RARRAY_PTR(result)[i] = RARRAY_PTR(ary)[NUM2LONG(nv)]; RB_GC_GUARD(ary);
for (i=0; i<n; i++) {
j = (long)(rb_genrand_real()*(len-i)) + i;
nv = RARRAY_PTR(result)[j];
RARRAY_PTR(result)[j] = RARRAY_PTR(result)[i];
RARRAY_PTR(result)[i] = nv;
}
} }
return result; return result;
} }