PWR081: Add benchmark

Author: alvrogd

Benchmark/src/CMakeLists.txt

@@ -20,3 +20,4 @@ if (OCB_Fortran_COMPILER_ID STREQUAL "GNU")
 endif()
 add_benchmark(PWR079)
 add_benchmark(PWR080)
+add_benchmark(PWR081)

Benchmark/src/PWR081.cpp

@@ -0,0 +1,43 @@
+#include "Benchmark.h"
+
+// Forward-declare the functions to benchmark
+extern "C" {
+double compute_stats_f(const int n, const double *data, double *mean,
+                       double *stddev);
+double compute_stats_improved_f(const int n, const double *data, double *mean,
+                                double *stddev);
+}
+
+// Size adjusted to fit execution on micro-seconds
+constexpr int N = 1024 * 1024;
+
+#if OCB_ENABLE_Fortran
+
+static void FortranExampleBench(benchmark::State &state) {
+  auto array = OpenCatalog::CreateRandomVector<double>(N);
+
+  for (auto _ : state) {
+    double mean, stddev;
+    compute_stats_f(N, array.data(), &mean, &stddev);
+    benchmark::DoNotOptimize(mean);
+    benchmark::DoNotOptimize(stddev);
+  }
+}
+
+static void FortranImprovedBench(benchmark::State &state) {
+  auto array = OpenCatalog::CreateRandomVector<double>(N);
+
+  for (auto _ : state) {
+    double mean, stddev;
+    compute_stats_improved_f(N, array.data(), &mean, &stddev);
+    benchmark::DoNotOptimize(mean);
+    benchmark::DoNotOptimize(stddev);
+  }
+}
+
+// The goal of these benchmarks is to demonstrate that the suggested check does
+// not incur any performance penalty
+OC_BENCHMARK("PWR081 Fortran Example", FortranExampleBench);
+OC_BENCHMARK("PWR081 Fortran Improved", FortranImprovedBench);
+
+#endif

Checks/PWR081/benchmark/example.f90

@@ -0,0 +1,29 @@
+! PWR081: Uninitialized output arguments can lead to undefined behavior
+
+! NOT-PWR070: Explicit-shape arrays used for C-interoperability
+pure subroutine compute_stats_f(n, data, mean, stddev) bind(c)
+  use iso_c_binding, only: c_double, c_int
+  implicit none
+
+  integer(kind=c_int), intent(in), value :: n
+  real(kind=c_double), dimension(n), intent(in) :: data
+  real(kind=c_double), intent(out) :: mean
+  real(kind=c_double), intent(out) :: stddev
+
+  integer(kind=c_int) :: i
+
+  ! We can't compute stddev from a single data point
+  if (n <= 1) then
+    return
+  end if
+
+  ! Also abort if there are invalid data points
+  do i = 1, n
+    if (data(i) < -900.0) then
+      return
+    end if
+  end do
+
+  mean = sum(data) / n
+  stddev = sqrt(sum((data - mean)**2) / (n - 1))
+end subroutine compute_stats_f

Checks/PWR081/benchmark/solution.f90

@@ -0,0 +1,32 @@
+! PWR081: Uninitialized output arguments can lead to undefined behavior
+
+! NOT-PWR070: Explicit-shape arrays used for C-interoperability
+pure subroutine compute_stats_improved_f(n, data, mean, stddev) bind(c)
+  use iso_c_binding, only: c_double, c_int
+  implicit none
+
+  integer(kind=c_int), intent(in), value :: n
+  real(kind=c_double), dimension(n), intent(in) :: data
+  real(kind=c_double), intent(out) :: mean
+  real(kind=c_double), intent(out) :: stddev
+
+  integer(kind=c_int) :: i
+
+  mean = 0.0
+  stddev = 0.0
+
+  ! We can't compute stddev from a single data point
+  if (n <= 1) then
+    return
+  end if
+
+  ! Also abort if there are invalid data points
+  do i = 1, n
+    if (data(i) < -900.0) then
+      return
+    end if
+  end do
+
+  mean = sum(data) / n
+  stddev = sqrt(sum((data - mean)**2) / (n - 1))
+end subroutine compute_stats_improved_f