Improve threads demo test/threads.cxx (#1263)
- Replace Fl_Browser with Fl_Terminal which uses a constant buffer size - Don't lock the GUI for every single prime. Collect primes for at least 0.25 seconds before calling Fl::awake(handler, buffer) - Use (two) alternate buffers for collecting prime data. - Use Fl::lock() *only* to protect thread data at initialization time. Observation on Debian 12, CPU: 12-core, 12th Gen Intel Core i7-1260P: speedup > factor 4, using multiple cores, GUI fully functional: scrolling the display, resizing, ... Tested natively (X11 + Wayland) and cross-compiled for Windows, using `wine`.
This commit is contained in:
Albrecht Schlosser
parent
acd77fa8dc
commit
088d98389c
152
test/threads.cxx
152
test/threads.cxx
@ -1,7 +1,7 @@
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//
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// Threading example program for the Fast Light Tool Kit (FLTK).
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//
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// Copyright 1998-2018 by Bill Spitzak and others.
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// Copyright 1998-2025 by Bill Spitzak and others.
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//
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// This library is free software. Distribution and use rights are outlined in
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// the file "COPYING" which should have been included with this file. If this
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@ -19,77 +19,123 @@
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#if defined(HAVE_PTHREAD) || defined(_WIN32)
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# include <FL/Fl.H>
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# include <FL/Fl_Double_Window.H>
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# include <FL/Fl_Browser.H>
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# include <FL/Fl_Terminal.H>
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# include <FL/Fl_Value_Output.H>
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# include <FL/fl_ask.H>
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# include "threads.h"
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# include <stdio.h>
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# include <math.h>
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# include <vector>
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// min. time in seconds before calling Fl::awake(...)
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#define DELTA 0.25
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// struct to collect primes until at least <DELTA> seconds passed.
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// Two such structs per thread are used as alternate buffers.
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struct prime {
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int idx; // thread index: 0 or {1..6}
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int done; // set to 1 after it was worked on
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Fl_Terminal *terminal; // widget to write output to
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Fl_Value_Output *value; // highest prime
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std::vector<unsigned long> primes; // collected primes within time frame
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};
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Fl_Thread prime_thread;
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Fl_Browser *browser1, *browser2;
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Fl_Terminal *tty1, *tty2;
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Fl_Value_Output *value1, *value2;
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int start2 = 3;
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void magic_number_cb(void *p)
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{
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void magic_number_cb(void *p) {
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Fl_Value_Output *w = (Fl_Value_Output*)p;
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w->labelcolor(FL_RED);
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w->redraw_label();
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}
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extern "C" void* prime_func(void* p)
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{
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Fl_Browser* browser = (Fl_Browser*) p;
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// This is called indirectly by Fl::awake(update_handler, (void *)prime)
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// in the context of the main (FLTK GUI) thread.
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void update_handler(void *v) {
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struct prime *pr = (struct prime *)v;
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for (auto n : pr->primes) {
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pr->terminal->printf("prime: %10u\n", n);
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if (n > pr->value->value())
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pr->value->value(n);
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}
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pr->done = 1;
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}
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extern "C" void* prime_func(void* p) {
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Fl_Terminal* terminal = (Fl_Terminal*)p;
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Fl_Value_Output *value;
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int n;
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unsigned long n;
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int step;
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char proud = 0;
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if (browser == browser2) {
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// initialize thread variables
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if (terminal == tty2) { // multiple threads
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Fl::lock(); // lock to prevent race condition on `start2`
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n = start2;
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start2 += 2;
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Fl::unlock();
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step = 12;
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value = value2;
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} else {
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} else { // single thread
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n = 3;
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step = 2;
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value = value1;
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}
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// initialize alternate buffers (struct prime) to store primes
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struct prime pr[2];
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pr[0].done = 0;
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pr[1].done = 1;
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pr[0].terminal = pr[1].terminal = terminal;
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pr[0].idx = pr[1].idx = n/2 - 1;
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pr[0].value = pr[1].value = value;
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pr[0].primes.clear();
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pr[1].primes.clear();
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int pi = 0; // prime buffer index
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Fl_Timestamp last = Fl::now();
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// very simple prime number calculator !
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//
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// The return at the end of this function can never be reached and thus
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// will generate a warning with some compilers, however we need to have
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// a return statement or other compilers will complain there is no return
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// statement. To avoid warnings on all compilers, we fool the smart ones
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// into beleiving that there is a chance that we reach the end by testing
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// n>=0, knowing that logically, n will never be negative in this context.
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if (n>=0) for (;;) {
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// statement. To avoid warnings on all compilers, we fool the smart ones into
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// believing that there is a chance that we reach the end by testing n > 0,
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// knowing that logically, n will never be less than 3 in this context.
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if (n > 0) for (;;) {
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int pp;
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int hn = (int)sqrt((double)n);
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for (pp = 3; pp <= hn; pp += 2) if ( n%pp == 0 ) break;
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if (pp >= hn) {
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char s[128];
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snprintf(s, 128, "%d", n);
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// Obtain a lock before we access the browser widget...
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Fl::lock();
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if (pp > hn) { // n is a prime
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browser->add(s);
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browser->bottomline(browser->size());
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if (n > value->value()) value->value(n);
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n += step;
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// Release the lock...
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Fl::unlock();
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pr[pi].primes.push_back(n);
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// Send a message to the main thread, at which point it will
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// process any pending redraws for our browser widget.
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Fl::awake();
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if (n>10000 && !proud) {
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// process any pending updates.
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double ssl = Fl::seconds_since(last);
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if (ssl > DELTA && pr[1-pi].done) { // ready to switch buffers
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last = Fl::now();
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Fl::awake(update_handler, (void *)(&pr[pi]));
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pi = 1 - pi; // switch to alternate buffer
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pr[pi].primes.clear(); // clear primes
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}
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n += step;
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if (n > 5*1000*1000 && !proud) {
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proud = 1;
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Fl::awake(magic_number_cb, value);
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}
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@ -107,40 +153,44 @@ extern "C" void* prime_func(void* p)
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int main(int argc, char **argv)
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{
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Fl_Double_Window* w = new Fl_Double_Window(200, 200, "Single Thread");
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browser1 = new Fl_Browser(0, 0, 200, 175);
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w->resizable(browser1);
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// First window: single thread
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Fl_Double_Window* w = new Fl_Double_Window(300, 200, "Single Thread");
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tty1 = new Fl_Terminal(0, 0, 300, 175);
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w->resizable(tty1);
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value1 = new Fl_Value_Output(100, 175, 200, 25, "Max Prime:");
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w->end();
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w->show(argc, argv);
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w = new Fl_Double_Window(200, 200, "Six Threads");
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browser2 = new Fl_Browser(0, 0, 200, 175);
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w->resizable(browser2);
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// Second window: multiple threads
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w = new Fl_Double_Window(300, 200, "Six Threads");
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tty2 = new Fl_Terminal(0, 0, 300, 175);
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w->resizable(tty2);
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value2 = new Fl_Value_Output(100, 175, 200, 25, "Max Prime:");
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w->end();
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w->show();
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browser1->add("Prime numbers:");
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browser2->add("Prime numbers:");
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tty1->printf("Prime numbers:\n");
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tty2->printf("Prime numbers:\n");
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// Enable multi-thread support by locking from the main thread.
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// Fl::wait() and Fl::run() call Fl::unlock() and Fl::lock() as needed
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// to release control to the child threads when it is safe to do so...
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// Enable multi-thread support by locking from the main
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// thread. Fl::wait() and Fl::run() call Fl::unlock() and
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// Fl::lock() as needed to release control to the child threads
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// when it is safe to do so...
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Fl::lock();
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// Start threads...
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// One thread displaying in one browser
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fl_create_thread(prime_thread, prime_func, browser1);
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// One thread displaying in one terminal
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fl_create_thread(prime_thread, prime_func, tty1);
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// Several threads displaying in another browser
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fl_create_thread(prime_thread, prime_func, browser2);
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fl_create_thread(prime_thread, prime_func, browser2);
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fl_create_thread(prime_thread, prime_func, browser2);
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fl_create_thread(prime_thread, prime_func, browser2);
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fl_create_thread(prime_thread, prime_func, browser2);
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fl_create_thread(prime_thread, prime_func, browser2);
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// Six threads displaying in another terminal
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fl_create_thread(prime_thread, prime_func, tty2);
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fl_create_thread(prime_thread, prime_func, tty2);
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fl_create_thread(prime_thread, prime_func, tty2);
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fl_create_thread(prime_thread, prime_func, tty2);
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fl_create_thread(prime_thread, prime_func, tty2);
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fl_create_thread(prime_thread, prime_func, tty2);
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Fl::run();
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