kc3-lang/SDL/test/testsem.c

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• Hash : 0d763800
  Author :
  Date : 2023-03-09T15:10:00
  

  Code style: changed "sizeof foo" to "sizeof(foo)" (thanks @sezero!) (cherry picked from commit c6443d86c92e962683a1efe5f123a144988875b5)

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• test/testsem.c

• /*
    Copyright (C) 1997-2023 Sam Lantinga <slouken@libsdl.org>
  
    This software is provided 'as-is', without any express or implied
    warranty.  In no event will the authors be held liable for any damages
    arising from the use of this software.
  
    Permission is granted to anyone to use this software for any purpose,
    including commercial applications, and to alter it and redistribute it
    freely.
  */
  
  /* Simple test of the SDL semaphore code */
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <signal.h>
  
  #include "SDL.h"
  
  #define NUM_THREADS 10
  /* This value should be smaller than the maximum count of the */
  /* semaphore implementation: */
  #define NUM_OVERHEAD_OPS      10000
  #define NUM_OVERHEAD_OPS_MULT 10
  
  static SDL_sem *sem;
  int alive;
  
  typedef struct Thread_State
  {
      SDL_Thread *thread;
      int number;
      SDL_bool flag;
      int loop_count;
      int content_count;
  } Thread_State;
  
  static void
  killed(int sig)
  {
      alive = 0;
  }
  
  static int SDLCALL
  ThreadFuncRealWorld(void *data)
  {
      Thread_State *state = (Thread_State *)data;
      while (alive) {
          SDL_SemWait(sem);
          SDL_Log("Thread number %d has got the semaphore (value = %" SDL_PRIu32 ")!\n",
                  state->number, SDL_SemValue(sem));
          SDL_Delay(200);
          SDL_SemPost(sem);
          SDL_Log("Thread number %d has released the semaphore (value = %" SDL_PRIu32 ")!\n",
                  state->number, SDL_SemValue(sem));
          ++state->loop_count;
          SDL_Delay(1); /* For the scheduler */
      }
      SDL_Log("Thread number %d exiting.\n", state->number);
      return 0;
  }
  
  static void
  TestRealWorld(int init_sem)
  {
      Thread_State thread_states[NUM_THREADS] = { { 0 } };
      int i;
      int loop_count;
  
      sem = SDL_CreateSemaphore(init_sem);
  
      SDL_Log("Running %d threads, semaphore value = %d\n", NUM_THREADS,
              init_sem);
      alive = 1;
      /* Create all the threads */
      for (i = 0; i < NUM_THREADS; ++i) {
          char name[64];
          (void)SDL_snprintf(name, sizeof(name), "Thread%u", (unsigned int)i);
          thread_states[i].number = i;
          thread_states[i].thread = SDL_CreateThread(ThreadFuncRealWorld, name, (void *)&thread_states[i]);
      }
  
      /* Wait 10 seconds */
      SDL_Delay(10 * 1000);
  
      /* Wait for all threads to finish */
      SDL_Log("Waiting for threads to finish\n");
      alive = 0;
      loop_count = 0;
      for (i = 0; i < NUM_THREADS; ++i) {
          SDL_WaitThread(thread_states[i].thread, NULL);
          loop_count += thread_states[i].loop_count;
      }
      SDL_Log("Finished waiting for threads, ran %d loops in total\n\n", loop_count);
  
      SDL_DestroySemaphore(sem);
  }
  
  static void
  TestWaitTimeout(void)
  {
      Uint32 start_ticks;
      Uint32 end_ticks;
      Uint32 duration;
      int retval;
  
      sem = SDL_CreateSemaphore(0);
      SDL_Log("Waiting 2 seconds on semaphore\n");
  
      start_ticks = SDL_GetTicks();
      retval = SDL_SemWaitTimeout(sem, 2000);
      end_ticks = SDL_GetTicks();
  
      duration = end_ticks - start_ticks;
  
      /* Accept a little offset in the effective wait */
      SDL_assert(duration > 1900 && duration < 2050);
      SDL_Log("Wait took %" SDL_PRIu32 " milliseconds\n\n", duration);
  
      /* Check to make sure the return value indicates timed out */
      if (retval != SDL_MUTEX_TIMEDOUT) {
          SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "SDL_SemWaitTimeout returned: %d; expected: %d\n\n", retval, SDL_MUTEX_TIMEDOUT);
      }
  
      SDL_DestroySemaphore(sem);
  }
  
  static void
  TestOverheadUncontended(void)
  {
      Uint32 start_ticks;
      Uint32 end_ticks;
      Uint32 duration;
      int i, j;
  
      sem = SDL_CreateSemaphore(0);
      SDL_Log("Doing %d uncontended Post/Wait operations on semaphore\n", NUM_OVERHEAD_OPS * NUM_OVERHEAD_OPS_MULT);
  
      start_ticks = SDL_GetTicks();
      for (i = 0; i < NUM_OVERHEAD_OPS_MULT; i++) {
          for (j = 0; j < NUM_OVERHEAD_OPS; j++) {
              SDL_SemPost(sem);
          }
          for (j = 0; j < NUM_OVERHEAD_OPS; j++) {
              SDL_SemWait(sem);
          }
      }
      end_ticks = SDL_GetTicks();
  
      duration = end_ticks - start_ticks;
      SDL_Log("Took %" SDL_PRIu32 " milliseconds\n\n", duration);
  
      SDL_DestroySemaphore(sem);
  }
  
  static int SDLCALL
  ThreadFuncOverheadContended(void *data)
  {
      Thread_State *state = (Thread_State *)data;
  
      if (state->flag) {
          while (alive) {
              if (SDL_SemTryWait(sem) == SDL_MUTEX_TIMEDOUT) {
                  ++state->content_count;
              }
              ++state->loop_count;
          }
      } else {
          while (alive) {
              /* Timeout needed to allow check on alive flag */
              if (SDL_SemWaitTimeout(sem, 50) == SDL_MUTEX_TIMEDOUT) {
                  ++state->content_count;
              }
              ++state->loop_count;
          }
      }
      return 0;
  }
  
  static void
  TestOverheadContended(SDL_bool try_wait)
  {
      Uint32 start_ticks;
      Uint32 end_ticks;
      Uint32 duration;
      Thread_State thread_states[NUM_THREADS] = { { 0 } };
      char textBuffer[1024];
      int loop_count;
      int content_count;
      int i, j;
      size_t len;
  
      sem = SDL_CreateSemaphore(0);
      SDL_Log("Doing %d contended %s operations on semaphore using %d threads\n",
              NUM_OVERHEAD_OPS * NUM_OVERHEAD_OPS_MULT, try_wait ? "Post/TryWait" : "Post/WaitTimeout", NUM_THREADS);
      alive = 1;
      /* Create multiple threads to starve the semaphore and cause contention */
      for (i = 0; i < NUM_THREADS; ++i) {
          char name[64];
          (void)SDL_snprintf(name, sizeof(name), "Thread%u", (unsigned int)i);
          thread_states[i].flag = try_wait;
          thread_states[i].thread = SDL_CreateThread(ThreadFuncOverheadContended, name, (void *)&thread_states[i]);
      }
  
      start_ticks = SDL_GetTicks();
      for (i = 0; i < NUM_OVERHEAD_OPS_MULT; i++) {
          for (j = 0; j < NUM_OVERHEAD_OPS; j++) {
              SDL_SemPost(sem);
          }
          /* Make sure threads consumed everything */
          while (SDL_SemValue(sem)) {
              /* Friendlier with cooperative threading models */
              SDL_Delay(1);
          }
      }
      end_ticks = SDL_GetTicks();
  
      alive = 0;
      loop_count = 0;
      content_count = 0;
      for (i = 0; i < NUM_THREADS; ++i) {
          SDL_WaitThread(thread_states[i].thread, NULL);
          loop_count += thread_states[i].loop_count;
          content_count += thread_states[i].content_count;
      }
      SDL_assert_release((loop_count - content_count) == NUM_OVERHEAD_OPS * NUM_OVERHEAD_OPS_MULT);
  
      duration = end_ticks - start_ticks;
      SDL_Log("Took %" SDL_PRIu32 " milliseconds, threads %s %d out of %d times in total (%.2f%%)\n",
              duration, try_wait ? "where contended" : "timed out", content_count,
              loop_count, ((float)content_count * 100) / loop_count);
      /* Print how many semaphores where consumed per thread */
      (void)SDL_snprintf(textBuffer, sizeof(textBuffer), "{ ");
      for (i = 0; i < NUM_THREADS; ++i) {
          if (i > 0) {
              len = SDL_strlen(textBuffer);
              (void)SDL_snprintf(textBuffer + len, sizeof(textBuffer) - len, ", ");
          }
          len = SDL_strlen(textBuffer);
          (void)SDL_snprintf(textBuffer + len, sizeof(textBuffer) - len, "%d", thread_states[i].loop_count - thread_states[i].content_count);
      }
      len = SDL_strlen(textBuffer);
      (void)SDL_snprintf(textBuffer + len, sizeof(textBuffer) - len, " }\n");
      SDL_Log("%s\n", textBuffer);
  
      SDL_DestroySemaphore(sem);
  }
  
  int main(int argc, char **argv)
  {
      int init_sem;
  
      /* Enable standard application logging */
      SDL_LogSetPriority(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO);
  
      if (argc < 2) {
          SDL_Log("Usage: %s init_value\n", argv[0]);
          return 1;
      }
  
      /* Load the SDL library */
      if (SDL_Init(0) < 0) {
          SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't initialize SDL: %s\n", SDL_GetError());
          return 1;
      }
      (void)signal(SIGTERM, killed);
      (void)signal(SIGINT, killed);
  
      init_sem = SDL_atoi(argv[1]);
      if (init_sem > 0) {
          TestRealWorld(init_sem);
      }
  
      TestWaitTimeout();
  
      TestOverheadUncontended();
  
      TestOverheadContended(SDL_FALSE);
  
      TestOverheadContended(SDL_TRUE);
  
      SDL_Quit();
      return 0;
  }
  

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