Bug #252

Array#sort doesn't respect overridden <=>

Added by Ryan Davis over 6 years ago. Updated almost 4 years ago.

[ruby-core:17708]
Status:Closed
Priority:Normal
Assignee:Yukihiro Matsumoto
ruby -v: Backport:

Description

=begin
We had this issue reported against rubinius. We're not sure whether it is a bug or a feature in MRI.

class String
def <=>(other)
self.length <=> other.length
end
end

junk = %w[these words should be sorted in the order of their length]
puts junk.sort

MRI (1.8, 1.9) does not respect new behavior of <=>.

Bug or feature?
=end

History

#1 Updated by Ryan Davis over 6 years ago

=begin
I guess I should ask: bug, feature, or undefined behavior?
=end

#2 Updated by Dave Thomas over 6 years ago

=begin

On Jul 9, 2008, at 6:00 PM, Ryan Davis wrote:

junk = %w[these words should be sorted in the order of their length]
puts junk.sort

MRI (1.8, 1.9) does not respect new behavior of <=>.

Bug or feature?

I seem to remember this from a while back--I seem to remember that

String is special-cased for performance.

=end

#3 Updated by Ryan Davis over 6 years ago

=begin

On Jul 9, 2008, at 17:27 , Dave Thomas wrote:

On Jul 9, 2008, at 6:00 PM, Ryan Davis wrote:

junk = %w[these words should be sorted in the order of their length]
puts junk.sort

MRI (1.8, 1.9) does not respect new behavior of <=>.

Bug or feature?

I seem to remember this from a while back--I seem to remember that

String is special-cased for performance.

and that's cool... but I'd like an "official" weigh in describing it

as either specification or implementation detail. ATM, I don't think

rubinius would see a performance loss if it respected the overridden

<=> method.

=end

#4 Updated by Vladimir Sizikov over 6 years ago

=begin
This seems to be a common performance trick in MRI, esp. for Fixnums and Strings.

Looking at array.c (sort_2), indeed Fixnums and Strings are special-cased.

I also checked JRuby, and JRuby follows what MRI does (and this does improve performance for Fixnum and String arrays).
=end

#5 Updated by Nobuyoshi Nakada over 6 years ago

=begin
Hi,

At Thu, 10 Jul 2008 16:44:33 +0900,
Vladimir Sizikov wrote in :

This seems to be a common performance trick in MRI, esp. for Fixnums and Strings.

Looking at array.c (sort_2), indeed Fixnums and Strings are special-cased.

I've forgotten to post this patch.

Index: intern.h
===================================================================
--- intern.h (revision 18354)
+++ intern.h (working copy)
@@ -168,4 +168,5 @@ void rb_alias ((VALUE, ID, ID));
void rb_attr _((VALUE,ID,int,int,int));
int rb_method_boundp _((VALUE, ID, int));
+int rb_method_basic_definition_p _((VALUE, ID));
VALUE rb_dvar_defined _((ID));
VALUE rb_dvar_curr _((ID));
Index: array.c
===================================================================
--- array.c (revision 18354)
+++ array.c (working copy)
@@ -1686,6 +1686,24 @@ struct ary
sort_data {
VALUE *ptr;
long len;
+ int opt_methods;
+ int opt_inited;
};

+enum {
+ sort_opt_Fixnum,
+ sort_opt_String,
+ sort_optimizable_count
+};
+
+#define STRING_P(s) (TYPE(s) == T_STRING && CLASS_OF(s) == rb_cString)
+
+#define SORT_OPTIMIZABLE_BIT(type) (1U << TOKEN_PASTE(sort_opt_,type))
+#define SORT_OPTIMIZABLE(data, type) \
+ ((data->opt_inited & SORT_OPTIMIZABLE_BIT(type)) ? \
+ (data->opt_methods & SORT_OPTIMIZABLE_BIT(type)) : \
+ ((data->opt_inited |= SORT_OPTIMIZABLE_BIT(type)), \
+ rb_method_basic_definition_p(TOKEN_PASTE(rb_c,type), id_cmp) && \
+ (data->opt_methods |= SORT_OPTIMIZABLE_BIT(type))))
+
static void
ary_sort_check(data)
@@ -1719,11 +1737,11 @@ sort_2(ap, bp, data)
int n;

  • if (FIXNUM_P(a) && FIXNUM_P(b)) {
  • if (FIXNUM_P(a) && FIXNUM_P(b) && SORT_OPTIMIZABLE(data, Fixnum)) { if ((long)a > (long)b) return 1; if ((long)a < (long)b) return -1; return 0; }
  • if (TYPE(a) == T_STRING) {
  • if (TYPE(b) == T_STRING) return rb_str_cmp(a, b);
  • if (STRING_P(a) && STRING_P(b) && SORT_OPTIMIZABLE(data, String)) {
  • return rb_str_cmp(a, b);
    }

    @@ -1743,4 +1761,6 @@ sort_internal(ary)
    data.ary = ary;
    data.ptr = RARRAY(ary)->ptr; data.len = RARRAY(ary)->len;

  • data.opt_methods = 0;

  • data.opt_inited = 0;
    qsort(RARRAY(ary)->ptr, RARRAY(ary)->len, sizeof(VALUE),
    rb_block_given_p()?sort_1:sort_2, &data);

    Index: eval.c

    --- eval.c (revision 18355)
    +++ eval.c (working copy)
    @@ -405,6 +405,7 @@ static ID id, send, respond_to;

    #define NOEX_TAINTED 8
    -#define NOEX_SAFE(n) ((n) >> 4)
    -#define NOEX_WITH(n, v) ((n) | (v) << 4)
    +#define NOEX_BASIC 16
    +#define NOEX_SAFE(n) ((n) >> 5)
    +#define NOEX_WITH(n, v) ((n) | (v) << 5 | (ruby_running ? 0 : NOEX_BASIC))
    #define NOEX_WITH_SAFE(n) NOEX_WITH(n, ruby_safe_level)

    @@ -4218,5 +4219,14 @@ module_setup(module, n)
    }

    -static NODE *basic_respond_to = 0;
    +int
    +rb_method_basic_definition_p(klass, id)

  • VALUE klass;

  • ID id;
    +{

  • NODE *node = rb_method_node(klass, id);

  • if (node && (node->nd_noex & NOEX_BASIC))

  • return 1;

  • return 0;
    +}

    int
    @@ -4228,5 +4238,5 @@ rb_obj_respond_to(obj, id, priv)
    VALUE klass = CLASS_OF(obj);

  • if (rb_method_node(klass, respond_to) == basic_respond_to) {

  • if (rb_method_basic_definition_p(klass, respond_to)) {
    return rb_method_boundp(klass, id, !priv);
    }
    @@ -8185,6 +8195,4 @@ Init_eval()
    rb_define_method(rb_mKernel, "respond_to?", obj_respond_to, -1);
    respond_to = rb_intern("respond_to?");

  • rb_global_variable((void *)&basic_respond_to);

  • basic_respond_to = rb_method_node(rb_cObject, respond_to);

    rb_define_global_function("raise", rb_f_raise, -1);

    Index: include/ruby/intern.h

    --- include/ruby/intern.h (revision 18354)
    +++ include/ruby/intern.h (working copy)
    @@ -250,4 +250,5 @@ void rb_alias(VALUE, ID, ID);
    void rb_attr(VALUE,ID,int,int,int);
    int rb_method_boundp(VALUE, ID, int);
    +int rb_method_basic_definition_p(VALUE, ID);
    VALUE rb_eval_cmd(VALUE, VALUE, int);
    int rb_obj_respond_to(VALUE, ID, int);

    Index: include/ruby/node.h

    --- include/ruby/node.h (revision 18354)
    +++ include/ruby/node.h (working copy)
    @@ -464,5 +464,6 @@ typedef struct RNode {
    #define NOEX_PRIVATE 0x02
    #define NOEX_PROTECTED 0x04
    -#define NOEX_MASK 0x06 /* 1110 /
    +#define NOEX_MASK 0x06 /
    0110 */
    +#define NOEX_BASIC 0x08

    #define NOEX_UNDEF NOEX_NOSUPER
    @@ -473,5 +474,5 @@ typedef struct RNode {

    #define NOEX_SAFE(n) (((n) >> 8) & 0x0F)
    -#define NOEX_WITH(n, s) ((s << 8) | n)
    +#define NOEX_WITH(n, s) ((s << 8) | (n) | (ruby_running ? 0 : NOEX_BASIC))
    #define NOEX_WITH_SAFE(n) NOEX_WITH(n, rb_safe_level())

    Index: array.c

    --- array.c (revision 18354)
    +++ array.c (working copy)
    @@ -1447,8 +1447,30 @@ rb_ary_reverse_m(VALUE ary)
    }

    +struct ary_sort_data {

  • VALUE ary;

  • int opt_methods;

  • int opt_inited;
    +};
    +
    +enum {

  • sort_opt_Fixnum,

  • sort_opt_String,

  • sort_optimizable_count
    +};
    +
    +#define STRING_P(s) (TYPE(s) == T_STRING && CLASS_OF(s) == rb_cString)
    +
    +#define SORT_OPTIMIZABLE_BIT(type) (1U << TOKEN_PASTE(sort_opt_,type))
    +#define SORT_OPTIMIZABLE(data, type) \

  • ((data->opt_inited & SORT_OPTIMIZABLE_BIT(type)) ? \

  • (data->opt_methods & SORT_OPTIMIZABLE_BIT(type)) : \
    
  • ((data->opt_inited |= SORT_OPTIMIZABLE_BIT(type)), \
    
  •  rb_method_basic_definition_p(TOKEN_PASTE(rb_c,type), id_cmp) && \
    
  •  (data->opt_methods |= SORT_OPTIMIZABLE_BIT(type))))
    

    +
    static VALUE
    -sort_reentered(VALUE *klass)
    +sort_reentered(VALUE ary)
    {

  • if (*klass) {

  • if (RBASIC(ary)->klass) {
    rb_raise(rb_eRuntimeError, "sort reentered");
    }
    @@ -1459,5 +1481,6 @@ static int
    sort_1(const void *ap, const void *bp, void *dummy)
    {

  • VALUE retval = sort_reentered(dummy);

  • struct ary_sort_data *data = dummy;

  • VALUE retval = sort_reentered(data->ary);
    VALUE a = *(const VALUE *)ap, b = *(const VALUE *)bp;
    int n;
    @@ -1465,5 +1488,5 @@ sort_1(const void *ap, const void *bp, v
    retval = rb_yield_values(2, a, b);
    n = rb_cmpint(retval, a, b);

  • sort_reentered(dummy);

  • sort_reentered(data->ary);
    return n;
    }
    @@ -1472,20 +1495,21 @@ static int
    sort_2(const void *ap, const void *bp, void *dummy)
    {

  • VALUE retval = sort_reentered(dummy);

  • struct ary_sort_data *data = dummy;

  • VALUE retval = sort_reentered(data->ary);
    VALUE a = *(const VALUE *)ap, b = *(const VALUE *)bp;
    int n;

  • if (FIXNUM_P(a) && FIXNUM_P(b)) {

  • if (FIXNUM_P(a) && FIXNUM_P(b) && SORT_OPTIMIZABLE(data, Fixnum)) {
    if ((long)a > (long)b) return 1;
    if ((long)a < (long)b) return -1;
    return 0;
    }

  • if (TYPE(a) == T_STRING) {

  • if (TYPE(b) == T_STRING) return rb_str_cmp(a, b);

  • if (STRING_P(a) && STRING_P(b) && SORT_OPTIMIZABLE(data, String)) {

  • return rb_str_cmp(a, b);
    }

    retval = rb_funcall(a, id_cmp, 1, b);
    n = rb_cmpint(retval, a, b);

  • sort_reentered(dummy);

  • sort_reentered(data->ary);

    return n;
    @@ -1514,8 +1538,12 @@ rb_ary_sort_bang(VALUE ary)
    if (RARRAY_LEN(ary) > 1) {
    VALUE tmp = ary_make_shared(ary);

  • struct ary_sort_data data;

    RBASIC(tmp)->klass = 0;

  • data.ary = tmp;

  • data.opt_methods = 0;

  • data.opt_inited = 0;
    ruby_qsort(RARRAY_PTR(tmp), RARRAY_LEN(tmp), sizeof(VALUE),

  •     rb_block_given_p()?sort_1:sort_2, &RBASIC(tmp)->klass);
    
  •     rb_block_given_p()?sort_1:sort_2, &data);
    

    if (RARRAY(ary)->ptr != RARRAY(tmp)->ptr) {
    if (!ARY_SHARED_P(ary)) xfree(RARRAY(ary)->ptr);

    Index: vm_method.c

    --- vm_method.c (revision 18354)
    +++ vm_method.c (working copy)
    @@ -1045,4 +1045,13 @@ rb_mod_modfunc(int argc, VALUE *argv, VA
    }

    +int
    +rb_method_basic_definition_p(VALUE klass, ID id)
    +{

  • NODE *node = rb_method_node(klass, id);

  • if (node && (node->nd_noex & NOEX_BASIC))

  • return 1;

  • return 0;
    +}
    +
    /*

    • call-seq: @@ -1054,6 +1063,4 @@ rb_mod_modfunc(int argc, VALUE *argv, VA */

    -static NODE *basic_respond_to = 0;

    int
    rb_obj_respond_to(VALUE obj, ID id, int priv)
    @@ -1061,5 +1068,5 @@ rb_obj_respond_to(VALUE obj, ID id, int
    VALUE klass = CLASS_OF(obj);

  • if (rb_method_node(klass, idRespond_to) == basic_respond_to) {

  • if (rb_method_basic_definition_p(klass, idRespond_to)) {
    return rb_method_boundp(klass, id, !priv);
    }
    @@ -1109,6 +1116,4 @@ Init_eval_method(void)

    rb_define_method(rb_mKernel, "respond_to?", obj_respond_to, -1);

  • basic_respond_to = rb_method_node(rb_cObject, idRespond_to);

  • rb_register_mark_object((VALUE)basic_respond_to);

    rb_define_private_method(rb_cModule, "remove_method", rb_mod_remove_method, -1);

    Nobu Nakada

=end

#6 Updated by Yukihiro Matsumoto over 6 years ago

=begin
Hi,

In message "Re: Re: [Ruby 1.8 - Bug #252] Array#sort doesn't respect overridden <=>"
on Mon, 4 Aug 2008 15:44:50 +0900, Nobuyoshi Nakada nobu@ruby-lang.org writes:

|I've forgotten to post this patch.

Interesting. Could you apply the patch (to trunk)?

                        matz.

=end

#7 Updated by Yukihiro Matsumoto over 6 years ago

=begin
Hi,

In message "Re: Re: [Ruby 1.8 - Bug #252] Array#sort doesn't respect overridden <=>"
on Fri, 8 Aug 2008 06:17:41 +0900, Lin Jen-Shin godfat@gmail.com writes:

|And should this behavior apply to condition (e.g. if, unless, while, etc.)
|to call :nil? as well?

No.

                        matz.

=end

#8 Updated by Yukihiro Matsumoto over 6 years ago

=begin
Hi,

In message "Re: Re: [Ruby 1.8 - Bug #252] Array#sort doesn't respect overridden <=>"
on Tue, 5 Aug 2008 04:49:27 +0900, Charles Oliver Nutter charles.nutter@sun.com writes:

|So this is going to be a behavioral change now? My reading of the patch
|tells me it's now checking to see if <=> has been overridden and if so
|using the path that actually calls it. As Ryan pointed out, this would
|be new behavior. Can we get an official ruling on what is correct in 1.8
|and 1.9.x?

We are not going to change 1.8 semantic in the near future. We should
keep compatibility, even when it's inconsistent, as long as it's not
"wrong".

For 1.9, I think it's better to adopt the new behavior. What do you
think?

                        matz.

=end

#9 Updated by Ryan Davis about 6 years ago

=begin
If this patch was applied, we should close the bug.
=end

#10 Updated by Yukihiro Matsumoto about 6 years ago

  • Status changed from Open to Closed

=begin
patch already applied.
=end

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