\(\newcommand{\W}[1]{ \; #1 \; }\) \(\newcommand{\R}[1]{ {\rm #1} }\) \(\newcommand{\B}[1]{ {\bf #1} }\) \(\newcommand{\D}[2]{ \frac{\partial #1}{\partial #2} }\) \(\newcommand{\DD}[3]{ \frac{\partial^2 #1}{\partial #2 \partial #3} }\) \(\newcommand{\Dpow}[2]{ \frac{\partial^{#1}}{\partial {#2}^{#1}} }\) \(\newcommand{\dpow}[2]{ \frac{ {\rm d}^{#1}}{{\rm d}\, {#2}^{#1}} }\)
multi_newton_takedown¶
Take Down Multi-threaded Newton Method¶
Thread¶
It is assumed that this function is called by thread zero, and all the other threads have completed their work and are blocked (waiting).
xout¶
See multi_newton_run .
Source¶
namespace {
bool multi_newton_takedown(vector<double>& xout)
{ // number of threads in the calculation
size_t num_threads = std::max(num_threads_, size_t(1));
// remove duplicates and points that are not solutions
xout.resize(0);
bool ok = true;
ok &= thread_alloc::thread_num() == 0;
// initialize as more that sub_length_ / 2 from any possible solution
double xlast = - sub_length_;
for(size_t thread_num = 0; thread_num < num_threads; thread_num++)
{ vector<double>& x = work_all_[thread_num]->x;
size_t i;
for(i = 0; i < x.size(); i++)
{ // check for case where this point is lower limit for this
// thread and upper limit for previous thread
if( fabs(x[i] - xlast) >= sub_length_ )
{ xout.push_back( x[i] );
xlast = x[i];
}
else
{ double fcur, flast, df;
fun_(x[i], fcur, df);
fun_(xlast, flast, df);
if( fabs(fcur) < fabs(flast) )
{ xout[ xout.size() - 1] = x[i];
xlast = x[i];
}
}
}
// check that this thread was ok with the work it did
ok &= work_all_[thread_num]->ok;
}
// go down so free memory for other threads before memory for master
size_t thread_num = num_threads;
while(thread_num--)
{
# if USE_THREAD_ALLOC_FOR_WORK_ALL
// call the destructor for vector destructor
work_all_[thread_num]->x.~vector<double>();
// delete the raw memory allocation
void* v_ptr = static_cast<void*>( work_all_[thread_num] );
thread_alloc::return_memory( v_ptr );
# else
delete work_all_[thread_num];
# endif
// Note that xout corresponds to memroy that is inuse by master
// (so we can only chech have freed all their memory).
if( thread_num > 0 )
{ // check that there is no longer any memory inuse by this thread
ok &= thread_alloc::inuse(thread_num) == 0;
// return all memory being held for future use by this thread
thread_alloc::free_available(thread_num);
}
}
// now we are done with the work_all_ vector so free its memory
// (because it is a static variable)
work_all_.clear();
return ok;
}
}