Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>There are two problems that are causing the segfault:</p> <p>1 - The functions <code>rb_big_*</code> sometimes doesn't return a <code>Bignum</code> object, but when you call then the first arg <strong>must</strong> be a <code>Bignum</code> object. For example:</p> <pre><code>if (rb_big_modulo(exp, CONST2BIGNUM(2))) { VALUE mul = rb_big_mul(res, base); // This maybe return a Fixnum res = rb_big_modulo(mul, mod); // This will cause a segfault :( } </code></pre> <p>2 - The function <code>rb_big_pow</code> when you call it with both args <code>Bignum</code>, it will warn you and will return a <code>Float</code> object where you can't convert easily to a <code>Bignum</code> object. So, you should replace the line where you call it by:</p> <pre><code>VALUE x = TO_BIGNUM(rb_big_pow(base, INT2NUM(2))); // Power by a Fixnum instead a Bignum base = TO_BIGNUM(rb_big_modulo(x , mod)); </code></pre> <p>The final implementation will be:</p> <pre><code>#define TO_BIGNUM(x) (FIXNUM_P(x) ? rb_int2big(FIX2LONG(x)) : x) #define CONST2BIGNUM(x) (TO_BIGNUM(INT2NUM(x))) VALUE method_big_power_mod(VALUE self, VALUE base, VALUE exp, VALUE mod){ VALUE res = TO_BIGNUM(INT2NUM(1)); base = TO_BIGNUM(base); exp = TO_BIGNUM(exp); mod = TO_BIGNUM(mod); while (rb_big_cmp(exp, CONST2BIGNUM(0))) { if (rb_big_modulo(exp, CONST2BIGNUM(2))) { VALUE mul = TO_BIGNUM(rb_big_mul(res, base)); res = TO_BIGNUM(rb_big_modulo(mul, mod)); } VALUE x = TO_BIGNUM(rb_big_pow(base, INT2NUM(2))); base = TO_BIGNUM(rb_big_modulo(x , mod)); exp = TO_BIGNUM(rb_big_div(exp, CONST2BIGNUM(2))); } return res; } </code></pre> <p>I don't know the performance impact with all these conversions. Maybe, you should test when it is a <code>Fixnum</code> or a <code>Bignum</code>and calculate it using the proper function or benchmark both approaches.</p> <p>When I ran it, I went thought an infinite loop, but I don't know if I call it with the correct values. </p>
    singulars
    1. This table or related slice is empty.
    1. PORuby native C big integer segfault
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USThiago Lewin
    1. USThiago Lewin
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PORuby native C big integer segfault
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. This table or related slice is empty.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload