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Make blueNorm threadsafe if C++11 atomics are available.

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This commit is contained in:
Rasmus Munk Larsen 2020-09-12 01:23:29 +00:00
parent adc861cabd
commit 71e08c702b
1 changed files with 29 additions and 3 deletions
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32
Eigen/src/Core/StableNorm.h
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@ -10,6 +10,10 @@
#ifndef EIGEN_STABLENORM_H
#define EIGEN_STABLENORM_H
#if EIGEN_HAS_CXX11_ATOMIC
#include <atomic>
#endif
namespace Eigen {
namespace internal {
@ -124,10 +128,29 @@ blueNorm_impl(const EigenBase<Derived>& _vec)
using std::sqrt;
using std::abs;
const Derived& vec(_vec.derived());
static bool initialized = false;
#if EIGEN_HAS_CXX11_ATOMIC
enum {
kNotInitialized = 0,
kInitializing = 1,
kInitialized = 2
};
static std::atomic<uint8_t> initialized{kNotInitialized};
#else
// Note: This is not theadsafe without C++11.
const bool kNotInitialized = false;
const bool kInitialized = true;
static bool initialized = kNotInitialized;
#endif
static RealScalar b1, b2, s1m, s2m, rbig, relerr;
if(!initialized)
while (initialized != kInitialized)
{
#if EIGEN_HAS_CXX11_ATOMIC
// Checking again to see if another thread has already initialized the constants.
uint8_t val = kNotInitialized;
if (initialized.compare_exchange_strong(val, kInitializing) && val != kInitialized) {
#endif
int ibeta, it, iemin, iemax, iexp;
RealScalar eps;
// This program calculates the machine-dependent constants
@ -156,7 +179,10 @@ blueNorm_impl(const EigenBase<Derived>& _vec)
eps = RealScalar(pow(double(ibeta), 1-it));
relerr = sqrt(eps); // tolerance for neglecting asml
initialized = true;
initialized = kInitialized;
#if EIGEN_HAS_CXX11_ATOMIC
}
#endif
}
Index n = vec.size();
RealScalar ab2 = b2 / RealScalar(n);