From 38089071300b8e04ed42236dd08d9055094fb3b8 Mon Sep 17 00:00:00 2001
From: Thomas White <taw@physics.org>
Date: Tue, 15 Nov 2011 12:05:55 +0100
Subject: Introduce "libcrystfel"

---
 libcrystfel/src/thread-pool.c | 283 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 283 insertions(+)
 create mode 100644 libcrystfel/src/thread-pool.c

(limited to 'libcrystfel/src/thread-pool.c')

diff --git a/libcrystfel/src/thread-pool.c b/libcrystfel/src/thread-pool.c
new file mode 100644
index 00000000..0ae26e17
--- /dev/null
+++ b/libcrystfel/src/thread-pool.c
@@ -0,0 +1,283 @@
+/*
+ * thread-pool.c
+ *
+ * A thread pool implementation
+ *
+ * (c) 2006-2011 Thomas White <taw@physics.org>
+ *
+ * Part of CrystFEL - crystallography with a FEL
+ *
+ */
+
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <assert.h>
+
+#ifdef HAVE_CPU_AFFINITY
+#include <sched.h>
+#endif
+
+
+#include "utils.h"
+
+
+/**
+ * SECTION:thread-pool
+ * @short_description: The thread pool
+ * @title: The thread pool
+ * @section_id:
+ * @see_also:
+ * @include: "thread-pool.h"
+ * @Image:
+ *
+ * The thread pool helps when running many tasks in parallel.  It takes care of
+ * starting and stopping threads, and presents a relatively simple interface to
+ * the individual programs.
+ */
+
+/* ------------------------------ CPU affinity ------------------------------ */
+
+#ifdef HAVE_CPU_AFFINITY
+
+static void set_affinity(int n, int cpu_num, int cpu_groupsize, int cpu_offset)
+{
+	cpu_set_t c;
+	int group;
+	int n_cpu_groups;
+	int i;
+
+	if ( cpu_num == 0 ) return;
+
+	CPU_ZERO(&c);
+
+	/* Work out which group this thread belongs to */
+	group = (n / cpu_groupsize) + cpu_offset;
+
+	/* Work out which CPUs should be used for this group */
+	n_cpu_groups = cpu_num / cpu_groupsize;
+	group = group % n_cpu_groups;
+
+	/* Set flags */
+	for ( i=0; i<cpu_groupsize; i++ ) {
+
+		int cpu = cpu_groupsize*group + i;
+
+		CPU_SET(cpu, &c);
+
+	}
+
+	if ( sched_setaffinity(0, sizeof(cpu_set_t), &c) ) {
+
+		/* Cannot use ERROR() just yet */
+		fprintf(stderr, "%i: Failed to set CPU affinity.\n", n);
+
+	}
+}
+
+#else /* HAVE_CPU_AFFINITY */
+
+static void set_affinity(int n, int cpu_num, int cpu_groupsize, int cpu_offset)
+{
+	/* Do absolutely nothing */
+}
+
+#endif /* HAVE_CPU_AFFINITY */
+
+
+/* --------------------------- Status label stuff --------------------------- */
+
+static int use_status_labels = 0;
+static pthread_key_t status_label_key;
+pthread_mutex_t stderr_lock = PTHREAD_MUTEX_INITIALIZER;
+
+struct worker_args
+{
+	struct task_queue_range *tqr;
+	struct task_queue *tq;
+	int id;
+	int cpu_num;
+	int cpu_groupsize;
+	int cpu_offset;
+};
+
+
+signed int get_status_label()
+{
+	int *cookie;
+
+	if ( !use_status_labels ) {
+		return -1;
+	}
+
+	cookie = pthread_getspecific(status_label_key);
+	return *cookie;
+}
+
+
+struct task_queue
+{
+	pthread_mutex_t  lock;
+
+	int              n_started;
+	int              n_completed;
+	int              max;
+
+	void *(*get_task)(void *);
+	void (*finalise)(void *, void *);
+	void *queue_args;
+	void (*work)(void *, int);
+};
+
+
+static void *task_worker(void *pargsv)
+{
+	struct worker_args *w = pargsv;
+	struct task_queue *q = w->tq;
+	int *cookie;
+
+	set_affinity(w->id, w->cpu_num, w->cpu_groupsize, w->cpu_offset);
+
+	cookie = malloc(sizeof(int));
+	*cookie = w->id;
+	pthread_setspecific(status_label_key, cookie);
+
+	free(w);
+
+	do {
+
+		void *task;
+		int cookie;
+
+		/* Get a task */
+		pthread_mutex_lock(&q->lock);
+		if ( (q->max) && (q->n_started >= q->max) ) {
+			pthread_mutex_unlock(&q->lock);
+			break;
+		}
+		task = q->get_task(q->queue_args);
+
+		/* No more tasks? */
+		if ( task == NULL ) {
+			pthread_mutex_unlock(&q->lock);
+			break;
+		}
+
+		q->n_started++;
+		pthread_mutex_unlock(&q->lock);
+
+		cookie = *(int *)pthread_getspecific(status_label_key);
+		q->work(task, cookie);
+
+		/* Update totals etc */
+		pthread_mutex_lock(&q->lock);
+		q->n_completed++;
+		if ( q->finalise ) {
+			q->finalise(q->queue_args, task);
+		}
+		pthread_mutex_unlock(&q->lock);
+
+	} while ( 1 );
+
+	free(cookie);
+
+	return NULL;
+}
+
+
+/**
+ * run_threads:
+ * @n_threads: The number of threads to run in parallel
+ * @work: The function to be called to do the work
+ * @get_task: The function which will determine the next unassigned task
+ * @final: The function which will be called to clean up after a task
+ * @queue_args: A pointer to any data required to determine the next task
+ * @max: Stop calling get_task after starting this number of jobs
+ * @cpu_num: The number of CPUs in the system
+ * @cpu_groupsize: The group size into which the CPUs are grouped
+ * @cpu_offset: The CPU group number at which to start pinning threads
+ *
+ * 'get_task' will be called every time a worker is idle.  It returns either
+ * NULL, indicating that no further work is available, or a pointer which will
+ * be passed to 'work'.
+ *
+ * 'final' will be called once per image, and will be given both queue_args
+ * and the last task pointer.
+ *
+ * 'get_task' and 'final' will be called only under lock, and so do NOT need to
+ * be re-entrant or otherwise thread safe.  'work', of course, needs to be
+ * thread safe.
+ *
+ * Work will stop after 'max' tasks have been processed whether get_task
+ * returned NULL or not.  If "max" is zero, all tasks will be processed.
+ *
+ * Returns: The number of tasks completed.
+ **/
+int run_threads(int n_threads, TPWorkFunc work,
+                TPGetTaskFunc get_task, TPFinalFunc final,
+                void *queue_args, int max,
+                int cpu_num, int cpu_groupsize, int cpu_offset)
+{
+	pthread_t *workers;
+	int i;
+	struct task_queue q;
+
+	pthread_key_create(&status_label_key, NULL);
+
+	workers = malloc(n_threads * sizeof(pthread_t));
+
+	pthread_mutex_init(&q.lock, NULL);
+	q.work = work;
+	q.get_task = get_task;
+	q.finalise = final;
+	q.queue_args = queue_args;
+	q.n_started = 0;
+	q.n_completed = 0;
+	q.max = max;
+
+	/* Now it's safe to start using the status labels */
+	if ( n_threads > 1 ) use_status_labels = 1;
+
+	/* Start threads */
+	for ( i=0; i<n_threads; i++ ) {
+
+		struct worker_args *w;
+
+		w = malloc(sizeof(struct worker_args));
+
+		w->tq = &q;
+		w->tqr = NULL;
+		w->id = i;
+		w->cpu_num = cpu_num;
+		w->cpu_groupsize = cpu_groupsize;
+		w->cpu_offset = cpu_offset;
+
+		if ( pthread_create(&workers[i], NULL, task_worker, w) ) {
+			/* Not ERROR() here */
+			fprintf(stderr, "Couldn't start thread %i\n", i);
+			n_threads = i;
+			break;
+		}
+
+	}
+
+	/* Join threads */
+	for ( i=0; i<n_threads; i++ ) {
+		pthread_join(workers[i], NULL);
+	}
+
+	use_status_labels = 0;
+
+	free(workers);
+
+	return q.n_completed;
+}
-- 
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