https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90384
Bug ID: 90384
Summary: std::transform fails to apply to all elements
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: mfdeakin at cs dot unc.edu
Target Milestone: ---
The following minimal reproducer fails randomly when using the par and
par_unseq execution policies, but passes when using the seq or just the default
transform.
(I don't know how to tag the following as code)
#include <algorithm>
#include <execution>
#include <assert.h>
int main(int argc, char **argv) {
constexpr int size = 1024;
std::vector<double> v(size);
for (int i = 0; i < size; i++) {
const double value = static_cast<double>(i);
v[i] = value * value + 5.0 * value;
}
constexpr double min_v = 1000000.0;
std::vector<bool> transform_par(size);
std::transform(std::execution::par, v.begin(), v.end(),
transform_par.begin(),
[](const double v) { return v >= min_v; });
std::vector<bool> transform_seq(size);
std::transform(std::execution::seq, v.begin(), v.end(),
transform_seq.begin(),
[](const double v) { return v >= min_v; });
auto [seq_diff, par_diff] = std::mismatch(transform_seq.begin(),
transform_seq.end(),
transform_par.begin(),
transform_par.end());
assert(seq_diff == transform_seq.end());
assert(par_diff == transform_par.end());
return 0;
}
This is with the version of the parallel stl included with GCC 9.1. My GCC
version is 9.1.1 20190503 (Red Hat 9.1.1-1). My version of tbb is
tbb-devel-2019.5-1.fc30.x86_64, which I believe is just the latest release,
2019 update 5.
