[Bug libstdc++/48114] [C++0x] binomial_distribution incorrect for p > .5 and geometric_distribution wrongly implements the TR1 definition
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48114 --- Comment #20 from Andrey Zholos 2011-03-16 22:43:45 UTC --- Good idea. The testcases should be adapted to the code paths in the GCC generators though: for instance, binomial with p > .5 isn't covered there. And BINS should be increased: for instance in the binomial(.3, 5500) testcase the most frequent outcomes are around 1650, but BINS only covers outcomes up to 100.
[Bug libstdc++/48114] [C++0x] binomial_distribution incorrect for p > .5 and geometric_distribution wrongly implements the TR1 definition
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48114 --- Comment #12 from Andrey Zholos 2011-03-14 18:07:22 UTC --- The double __p also fixes an infinite (maybe) loop in both binomial_distribution(100, .75) and binomial_distribution(100, .25) when _GLIBCXX_USE_C99_MATH_TR1 is defined. I guess the proper way to test the algorithms is to generate a lot of values and do a Pearson's chi-square test to check that the distribution is correct. Then that can be used to make a faster testcase for just a few values.
[Bug libstdc++/48114] [C++0x] binomial_distribution incorrect for p > .5 and geometric_distribution wrongly implements the TR1 definition
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48114 --- Comment #8 from Andrey Zholos 2011-03-14 17:34:01 UTC --- Ah, yes, I only looked at the C++0x formulas. By the way, testcases for these don't need to sample probabilities. They can just check, say, the first 100 values drawn using a deterministic generator.
[Bug libstdc++/48114] binomial_distribution incorrect for p > .5
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48114 --- Comment #4 from Andrey Zholos 2011-03-14 15:25:14 UTC --- Created attachment 23652 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23652 Probability table for geometric_distribution.
[Bug libstdc++/48114] binomial_distribution incorrect for p > .5
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48114
--- Comment #3 from Andrey Zholos 2011-03-14 15:23:25
UTC ---
I'll add this here since it's in the same place and the test will be
similar.
For geometric_distribution(.25) the first 10 probabilities are:
sample correct
p_0 0.000 0.250
p_1 0.750 0.188
p_2 0.187 0.141
p_3 0.046 0.105
p_4 0.012 0.079
p_5 0.003 0.059
p_6 0.001 0.044
p_7 0.000 0.033
p_8 0.000 0.025
p_9 0.000 0.019
The smallest value returned is 1, but should be 0 (and d.min() is
correctly 0); and p is used as 1-p.
Fix:
--- include/c++/bits/random.h
+++ include/c++/bits/random.h
@@ -3628,8 +3628,8 @@
void
_M_initialize()
- { _M_log_p = std::log(_M_p); }
+ { _M_log_1_p = std::log(1 - _M_p); }
double _M_p;
- double _M_log_p;
+ double _M_log_1_p;
};
--- include/c++/bits/random.tcc
+++ include/c++/bits/random.tcc
@@ -1027,3 +1027,3 @@
do
- __cand = std::ceil(std::log(__aurng()) / __param._M_log_p);
+ __cand = std::floor(std::log(__aurng()) / __param._M_log_1_p);
while (__cand >= __thr);
Also, there's a line in random.h
_GLIBCXX_DEBUG_ASSERT((_M_p >= 0.0)
&& (_M_p <= 1.0));
but the standard only requires 0 < p < 1.
[Bug libstdc++/48114] New: binomial_distribution incorrect for p > .5
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48114
Summary: binomial_distribution incorrect for p > .5
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: a...@althenia.net
Created attachment 23651
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23651
Probability table for binomial_distribution.
The attached program samples binomial_distribution(10, .75) and
calculates the correct probabilities of each outcome. The output shows
that the probabilities are reversed. With p > .5 the distribution should
be biased toward higher values.
sample correct
p_0 0.056 0.000
p_1 0.185 0.000
p_2 0.283 0.000
p_3 0.252 0.003
p_4 0.147 0.016
p_5 0.058 0.058
p_6 0.016 0.146
p_7 0.003 0.250
p_8 0.000 0.282
p_9 0.000 0.188
p_100.000 0.056
The problem is here, __param.p() is a double.
--- include/c++/bits/random.tcc
+++ include/c++/bits/random.tcc
@@ -1434,7 +1434,7 @@
{
result_type __ret;
const _IntType __t = __param.t();
- const _IntType __p = __param.p();
+ const double __p = __param.p();
const double __p12 = __p <= 0.5 ? __p : 1.0 - __p;
__detail::_Adaptor<_UniformRandomNumberGenerator, double>
__aurng(__urng);
[Bug c++/43281] [c++0x] ICE with invalid auto
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43281
Andrey Zholos changed:
What|Removed |Added
CC||aaz at althenia dot net
--- Comment #5 from Andrey Zholos 2010-10-17 12:10:12
UTC ---
This valid code triggers the new error message:
template
struct A {
int f();
void g() {
auto x = f(), y = x;
}
};
[Bug c++/42336] [c++0x] ICE with pointer-to-member-function decltype argument in template function
--- Comment #2 from aaz at althenia dot net 2009-12-10 00:07 --- To be more specific, it happens only with -O -fipa-sra -finline-small-functions -g -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42336
[Bug c++/42336] New: [c++0x] ICE with pointer-to-member-function decltype argument in template function
The following reduced program produces an ICE when compiled with
-std=c++0x -O2 -g.
=
struct X {
void func() {}
};
template
void b(T) {}
int main() {
b(X()); /* line 9 */
X().func();
return 0;
}
=
1.cc: In function 'void b(T) [with T = X, U = void (X::*)()]':
1.cc:9:9: internal compiler error: in build_ptrmem_type, at cp/decl.c:7202
And the following variation produces a different ICE.
===
struct X {
void func() {}
};
template
struct A {};
template
void b(T) {}
int main() {
b(A());
X().func();
return 0;
}
===
Internal compiler error: Error reporting routines re-entered.
--
Summary: [c++0x] ICE with pointer-to-member-function decltype
argument in template function
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: aaz at althenia dot net
GCC build triplet: x86_64-portbld-freebsd8.0
GCC host triplet: x86_64-portbld-freebsd8.0
GCC target triplet: x86_64-portbld-freebsd8.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42336
[Bug c++/40619] [c++0x] ICE on repeated decltype expression in auto functions
--- Comment #4 from aaz at althenia dot net 2009-07-04 12:54 --- It works. Thanks! -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40619
[Bug c++/40619] New: [c++0x] ICE on repeated decltype expression in auto functions
template struct X {};
template auto f(T t) -> X {}
template auto g(T t) -> X {}
Compiling with -std=c++0x gives
decltype_ice.cc:4:52: internal compiler error: Segmentation fault: 11
--
Summary: [c++0x] ICE on repeated decltype expression in auto
functions
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: aaz at althenia dot net
GCC build triplet: x86_64-portbld-freebsd7.2
GCC host triplet: x86_64-portbld-freebsd7.2
GCC target triplet: x86_64-portbld-freebsd7.2
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40619
