On 04/26/2017 05:16 AM, Jonathan Wakely wrote:
On 26/04/17 11:14 +0200, Paolo Carlini wrote:
.. or maybe using the wrong constant only impacts the performance?!?
Yes, I think so. I did some very simple sanity tests and the numbers
were identical before and after.
I was backporting this and saw that __generate_impl does this twice more.
For trunk and branch-8 I have these patches.
OK?
2018-05-07 Edward Smith-Rowland <3dw...@verizon.net>
Moar PR libstdc++/80506
* include/bits/random.tcc (gamma_distribution::__generate_impl()):
Fix magic number used in loop condition.
Index: include/bits/random.tcc
===================================================================
--- include/bits/random.tcc (revision 259965)
+++ include/bits/random.tcc (working copy)
@@ -2408,7 +2408,7 @@
__v = __v * __v * __v;
__u = __aurng();
}
- while (__u > result_type(1.0) - 0.331 * __n * __n * __n * __n
+ while (__u > result_type(1.0) - 0.0331 * __n * __n * __n * __n
&& (std::log(__u) > (0.5 * __n * __n + __a1
* (1.0 - __v + std::log(__v)))));
@@ -2429,7 +2429,7 @@
__v = __v * __v * __v;
__u = __aurng();
}
- while (__u > result_type(1.0) - 0.331 * __n * __n * __n * __n
+ while (__u > result_type(1.0) - 0.0331 * __n * __n * __n * __n
&& (std::log(__u) > (0.5 * __n * __n + __a1
* (1.0 - __v + std::log(__v)))));
