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Improve test/threads demo program (backported from 1.5)

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- use Fl_Terminal instead of Fl_Browser for prime display
- add Fl::lock()/Fl::unlock() at thread initialization
- format "Max Prime" output as integer number
- use a fixed font for better readability
- close all windows when the user closes one of them
- use standard background and text colors

Note: This commit is a compromise. The version in FLTK 1.5 uses
  std::vector<> and can't be fully backported to 1.4.
This commit is contained in:
Albrecht Schlosser 2025-07-14 17:00:23 +02:00
parent a5d2d19a23
commit 75f3bdfa55
1 changed files with 98 additions and 61 deletions
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159
test/threads.cxx
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@ -1,7 +1,7 @@
//
// Threading example program for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2018 by Bill Spitzak and others.
// Copyright 1998-2025 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file. If this
@ -19,8 +19,8 @@
#if defined(HAVE_PTHREAD) || defined(_WIN32)
# include <FL/Fl.H>
# include <FL/Fl_Double_Window.H>
# include <FL/Fl_Browser.H>
# include <FL/Fl_Value_Output.H>
# include <FL/Fl_Terminal.H>
# include <FL/Fl_Output.H>
# include <FL/fl_ask.H>
# include "threads.h"
# include <stdio.h>
@ -28,34 +28,39 @@
Fl_Thread prime_thread;
Fl_Browser *browser1, *browser2;
Fl_Value_Output *value1, *value2;
Fl_Terminal *tty1, *tty2;
Fl_Output *value1, *value2;
int start2 = 3;
void magic_number_cb(void *p)
{
Fl_Value_Output *w = (Fl_Value_Output*)p;
void magic_number_cb(void *p) {
Fl_Output *w = (Fl_Output*)p;
w->labelcolor(FL_RED);
w->redraw_label();
// if (w == value1) Fl::hide_all_windows(); // TEST: terminate early to measure time
}
extern "C" void* prime_func(void* p)
{
Fl_Browser* browser = (Fl_Browser*) p;
Fl_Value_Output *value;
int n;
extern "C" void* prime_func(void* p) {
Fl_Terminal* terminal = (Fl_Terminal*)p;
Fl_Output *value;
unsigned long n;
unsigned long max_value = 0;
int step;
char proud = 0;
char maxbuf[32];
if (browser == browser2) {
n = start2;
// initialize thread variables
if (terminal == tty2) { // multiple threads
Fl::lock(); // lock to prevent race condition on `start2`
n = start2;
start2 += 2;
step = 12;
value = value2;
} else {
n = 3;
step = 2;
value = value1;
Fl::unlock();
step = 12;
value = value2;
} else { // single thread
n = 3;
step = 2;
value = value1;
}
// very simple prime number calculator !
@ -63,35 +68,45 @@ extern "C" void* prime_func(void* p)
// The return at the end of this function can never be reached and thus
// will generate a warning with some compilers, however we need to have
// a return statement or other compilers will complain there is no return
// statement. To avoid warnings on all compilers, we fool the smart ones
// into beleiving that there is a chance that we reach the end by testing
// n>=0, knowing that logically, n will never be negative in this context.
if (n>=0) for (;;) {
// statement. To avoid warnings on all compilers, we fool the smart ones into
// believing that there is a chance that we reach the end by testing n > 0,
// knowing that logically, n will never be less than 3 in this context.
if (n > 0) for (;;) {
int pp;
int hn = (int)sqrt((double)n);
for (pp=3; pp<=hn; pp+=2) if ( n%pp == 0 ) break;
if (pp >= hn) {
char s[128];
snprintf(s, 128, "%d", n);
for (pp = 3; pp <= hn; pp += 2) {
if (n % pp == 0)
break;
}
if (pp > hn) { // n is a prime
// Obtain a lock before we access the terminal widget...
// Note: locking the GUI for each prime number is not recommended.
// A better (more efficient) solution has been implemented in FLTK 1.5
// Obtain a lock before we access the browser widget...
Fl::lock();
browser->add(s);
browser->bottomline(browser->size());
if (n > value->value()) value->value(n);
n += step;
terminal->printf("prime: %10u\n", n);
if (n > max_value) {
max_value = n;
snprintf(maxbuf, sizeof(maxbuf), "%9lu", max_value);
value->value(maxbuf);
}
// Release the lock...
Fl::unlock();
// Send a message to the main thread, at which point it will
// process any pending redraws for our browser widget. The
// message we pass here isn't used for anything, so we could also
// just pass NULL.
Fl::awake(p);
if (n>10000 && !proud) {
// Send a message to the main thread, at which point it will process
// any pending redraws for our terminal widget.
Fl::awake();
n += step;
if (n > 2 * 1000 * 1000 && !proud) {
proud = 1;
Fl::awake(magic_number_cb, value);
}
@ -107,42 +122,64 @@ extern "C" void* prime_func(void* p)
return 0L;
}
// close all windows when the user closes one of the windows
void close_cb(Fl_Widget *w, void *v) {
Fl::hide_all_windows();
printf("Max prime number with 1 thread : %s\n", value1->value());
printf("Max prime number with 6 threads: %s\n", value2->value());
return;
}
int main(int argc, char **argv)
{
// First window: single thread
Fl_Double_Window* w = new Fl_Double_Window(200, 200, "Single Thread");
browser1 = new Fl_Browser(0, 0, 200, 175);
w->resizable(browser1);
value1 = new Fl_Value_Output(100, 175, 200, 25, "Max Prime:");
tty1 = new Fl_Terminal(0, 0, 200, 175);
tty1->color(FL_BACKGROUND2_COLOR);
tty1->textcolor(FL_FOREGROUND_COLOR);
w->resizable(tty1);
value1 = new Fl_Output(100, 175, 98, 23, "Max Prime:");
value1->textfont(FL_COURIER);
w->callback(close_cb);
w->end();
w->show(argc, argv);
// Second window: multiple threads
w = new Fl_Double_Window(200, 200, "Six Threads");
browser2 = new Fl_Browser(0, 0, 200, 175);
w->resizable(browser2);
value2 = new Fl_Value_Output(100, 175, 200, 25, "Max Prime:");
tty2 = new Fl_Terminal(0, 0, 200, 175);
tty2->color(FL_BACKGROUND2_COLOR);
tty2->textcolor(FL_FOREGROUND_COLOR);
w->resizable(tty2);
value2 = new Fl_Output(100, 175, 98, 23, "Max Prime:");
value2->textfont(FL_COURIER);
w->callback(close_cb);
w->end();
w->show();
browser1->add("Prime numbers:");
browser2->add("Prime numbers:");
tty1->printf("Prime numbers:\n");
tty2->printf("Prime numbers:\n");
// Enable multi-thread support by locking from the main thread.
// Fl::wait() and Fl::run() call Fl::unlock() and Fl::lock() as needed
// to release control to the child threads when it is safe to do so...
// Enable multi-thread support by locking from the main
// thread. Fl::wait() and Fl::run() call Fl::unlock() and
// Fl::lock() as needed to release control to the child threads
// when it is safe to do so...
Fl::lock();
// Start threads...
// One thread displaying in one browser
fl_create_thread(prime_thread, prime_func, browser1);
// One thread displaying in one terminal
// Several threads displaying in another browser
fl_create_thread(prime_thread, prime_func, browser2);
fl_create_thread(prime_thread, prime_func, browser2);
fl_create_thread(prime_thread, prime_func, browser2);
fl_create_thread(prime_thread, prime_func, browser2);
fl_create_thread(prime_thread, prime_func, browser2);
fl_create_thread(prime_thread, prime_func, browser2);
fl_create_thread(prime_thread, prime_func, tty1);
// Six threads displaying in another terminal
fl_create_thread(prime_thread, prime_func, tty2);
fl_create_thread(prime_thread, prime_func, tty2);
fl_create_thread(prime_thread, prime_func, tty2);
fl_create_thread(prime_thread, prime_func, tty2);
fl_create_thread(prime_thread, prime_func, tty2);
fl_create_thread(prime_thread, prime_func, tty2);
Fl::run();