James E. King, III wrote:
For folks who like (potential) compiler optimization bugs:
https://svn.boost.org/trac10/ticket/13247
Looking at the source of independent_bits, this jumps out at me:
S = (S << w0) + (u & y0_mask);
and later
S = (S << (w0 + 1)) + (u & y1_mask);
Shifts with a value more than the number of bits are undefined, and
debugging confirms that w0 is 32 in the failing tests.
Possible fix:
C:\Projects\boost-git\boost\libs\random>git diff
diff --git a/include/boost/random/independent_bits.hpp
b/include/boost/random/independent_bits.hpp
index dec63b3..835ec32 100644
--- a/include/boost/random/independent_bits.hpp
+++ b/include/boost/random/independent_bits.hpp
@@ -159,7 +159,14 @@ public:
BOOST_ASSERT(n0*w0 + (n - n0)*(w0 + 1) == w);
result_type S = 0;
- for(std::size_t k = 0; k < n0; ++k) {
+ if(0 < n0) {
+ base_unsigned u;
+ do {
+ u = detail::subtract()(_base(),
(_base.min)());
+ } while(u > base_unsigned(y0 - 1));
+ S = (u & y0_mask);
+ }
+ for(std::size_t k = 1; k < n0; ++k) {
base_unsigned u;
do {
u = detail::subtract()(_base(),
(_base.min)()
);
I also see (unrelated) variant=release errors on msvc-12.0/msvc-14.0, but
haven't investigated them.
...failed testing.capture-output
..\..\bin.v2\libs\random\test\test_knuth_b.test\msvc-12.0\release\threadapi-win32\threading-multi\test_knuth_b.run...
...failed testing.capture-output
..\..\bin.v2\libs\random\test\test_ecuyer1988.test\msvc-12.0\release\threadapi-win32\threading-multi\test_ecuyer1988.run...
...failed testing.capture-output
..\..\bin.v2\libs\random\test\test_independent_bits31.test\msvc-12.0\release\threadapi-win32\threading-multi\test_independent_bits31.run...
...failed testing.capture-output
..\..\bin.v2\libs\random\test\test_ecuyer1988.test\msvc-14.0\release\threadapi-win32\threading-multi\test_ecuyer1988.run...
...failed testing.capture-output
..\..\bin.v2\libs\random\test\test_knuth_b.test\msvc-14.0\release\threadapi-win32\threading-multi\test_knuth_b.run...
...failed testing.capture-output
..\..\bin.v2\libs\random\test\test_independent_bits31.test\msvc-14.0\release\threadapi-win32\threading-multi\test_independent_bits31.run...
