Re: GThreads and GThreadPool help for a dummy

[richard boaz <ivor boaz gmail com>]

this is how i do it (not using pools), i have modified my code for your purposes, though it's probably wrong somewhere in the implementation details (i didn't even compile it), but i leave that to you.

this is very easily generalizable to do any kind of background work on a "list" of items.

richard

=== BEGIN code snippet ===

{ // in the main routine

gfloat *retPtr, tot_err;

GQueue *threadsQ = g_queue_new(); // Q holding list of data items to process

data_t data[N_DATAPOINTS]; // data items to process

fill_the_data_array(data);

for(i = 0;�

i < N_DATAPOINTS;

i++)

{

g_queue_push_head(threadsQ, &data[i]); // put data item onto Q for processing

}

g_thread_init(NULL);

commQ = g_async_queue_new(); // create comms Q�

threadsProc(threadsQ, maxThreads); // initiate threads

retPtr�= (g_float*) g_async_queue_pop(commQ); // sit and wait for all threads in threadsProc() to complete...

tot_err = *retPtr; // the answer

}

// all the rest in a different source file...

static GQueue *threadsQ; // Q holding the data to process

static int numThreads; // number of threads (and a counter too)

static g_float *tot_err; // array of g_float, one element per thread

static g_float total_errors; // total errors, added up, returned to main

static GStaticMutex QMutex = G_STATIC_MUTEX_INIT; // mutex to read Q

typedef struct _THREADARGS

{ // structure of arguments to thread proc

GThreadFunc returnFunc;

int threadNum;

} THREADARGS;

static void finishThreads()

{ // called once a thread has finished its work

numThreads--;

if (!numThreads)

{ // return to main routine

int i;

g_float retValue = 0;

for (i = 0;i<numThreads; i++)

retValue += tot_err[i];

total_errors = retValue;

g_async_queue_push(commQ, &total_errors);

}

}

static data_t *get_data()

{ // get the next data item off the Q to process, called by _addData()

data_t *data;

g_static_mutex_lock(&QMutex);

data = "">

g_static_mutex_unlock(&QMutex);

return (data);

}

static void _addData(THREADARGS *threadArgs)

{ // processing thread

int threadNum = threadArgs->threadNum;

GThreadFunc retFunc = threadArgs->returnFunc;

data_t *data = "" class="Apple-tab-span" style="white-space: pre; "> // get a data item to process

while�(data)

{

tot_err[threadNum] += calc_error(data);

data = "" class="Apple-tab-span" style="white-space: pre; "> // until no more to do

}

(*(retFunc))(NULL);

}

void threadsProc(GQueue *q, int nThreads)

{

int i;

numThreads = nThreads;

tot_err = calloc(numThreads, sizeof(g_float));

threadsQ = q;

for(i=0;i<numThreads;i++)

{

THREADARGS *threadArgs;

threadArgs = calloc(1, sizeof(THREADARGS));

threadArgs->returnFunc = (GThreadFunc) finishThreads;

threadArgs->threadNum = i;

g_thread_create((GThreadFunc) _addData, (void *) threadArgs, FALSE, NULL);�

}

}

=== END code snippet ===

2010/7/23 �stein Sch�g-Johansen <oystein gnubg org>

I tried, and the new problem is now:

�pool = g_thread_pool_new( my_calc, (gpointer) &common, 8, FALSE, &err );

�for (i = 0; i < n_tot; i++ )
� � � � �g_thread_pool_push( pool, &store[i], &err );

�g_thread_pool_free( pool, FALSE, TRUE );

When I run this code, it continues without waiting for the threads to
complete. I expected that the g_thread_pool_free function would make it wait
for all threads to complete before the program code continues, however
it does not! How can I make it wait?

(Yes, I added a static mutex in my_func. I'm convinced that I need it. )

-�stein
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