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Improve performance of Integer#digits

Browse source 
This speeds up performance by multiple orders of magnitude for
large integers.

Fixes [Bug #14391]

Co-authored-by: tompng (tomoya ishida) <tomoyapenguin@gmail.com>
This commit is contained in:
Jeremy Evans 2021-06-17 11:27:53 -07:00
parent 64ac984129
commit 9931e2f509
Notes: git 2021-07-30 07:19:38 +09:00 
Merged: https://github.com/ruby/ruby/pull/4584
2 changed files with 29 additions and 6 deletions
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33
numeric.c
View file

@ -4805,7 +4805,7 @@ rb_fix_digits(VALUE fix, long base)
static VALUE
rb_int_digits_bigbase(VALUE num, VALUE base)
{
VALUE digits;
VALUE digits, bases;
assert(!rb_num_negative_p(num));
@ -4823,11 +4823,32 @@ rb_int_digits_bigbase(VALUE num, VALUE base)
if (FIXNUM_P(num))
return rb_ary_new_from_args(1, num);
digits = rb_ary_new();
while (!FIXNUM_P(num) || FIX2LONG(num) > 0) {
VALUE qr = rb_int_divmod(num, base);
rb_ary_push(digits, RARRAY_AREF(qr, 1));
num = RARRAY_AREF(qr, 0);
if (int_lt(rb_int_div(rb_int_bit_length(num), rb_int_bit_length(base)), INT2FIX(50))) {
digits = rb_ary_new();
while (!FIXNUM_P(num) || FIX2LONG(num) > 0) {
VALUE qr = rb_int_divmod(num, base);
rb_ary_push(digits, RARRAY_AREF(qr, 1));
num = RARRAY_AREF(qr, 0);
}
return digits;
}
bases = rb_ary_new();
for (VALUE b = base; int_lt(b, num) == Qtrue; b = rb_int_mul(b, b)) {
rb_ary_push(bases, b);
}
digits = rb_ary_new_from_args(1, num);
while (RARRAY_LEN(bases)) {
VALUE b = rb_ary_pop(bases);
long i, last_idx = RARRAY_LEN(digits) - 1;
for(i = last_idx; i >= 0; i--) {
VALUE n = RARRAY_AREF(digits, i);
VALUE divmod = rb_int_divmod(n, b);
VALUE div = RARRAY_AREF(divmod, 0);
VALUE mod = RARRAY_AREF(divmod, 1);
if (i != last_idx || div != INT2FIX(0)) rb_ary_store(digits, 2 * i + 1, div);
rb_ary_store(digits, 2 * i, mod);
}
}
return digits;

2
test/ruby/test_integer.rb
View file

@ -576,6 +576,8 @@ class TestInteger < Test::Unit::TestCase
assert_equal([0, 9, 8, 7, 6, 5, 4, 3, 2, 1], 1234567890.digits)
assert_equal([90, 78, 56, 34, 12], 1234567890.digits(100))
assert_equal([10, 5, 6, 8, 0, 10, 8, 6, 1], 1234567890.digits(13))
assert_equal((2 ** 1024).to_s(7).chars.map(&:to_i).reverse, (2 ** 1024).digits(7))
assert_equal([0] * 100 + [1], (2 ** (128 * 100)).digits(2 ** 128))
end
def test_digits_for_negative_numbers