iOS多线程

int n = 200000000;

– (void)compute:(NSNumber *)aObject
{
    double sum = 0;
    for (int a = aObject.intValue; a < n ; a++)
    {
        sum = sum + a;
//        [self print:a];
    }
    [self performSelectorOnMainThread:@selector(updateLabel:) withObject:[NSNumber numberWithDouble:sum] waitUntilDone:NO];
}

– (void)thread1
{
    [NSThread detachNewThreadSelector:@selector(compute:) toTarget:self withObject:[NSNumber numberWithInt:i]];
}

– (void)thread2
{
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    
//group
    dispatch_group_t group = dispatch_group_create();
    dispatch_group_async(group, queue, ^{
        double sum = 0;
        for (int a = i; a < n  ; a++)
        {
            sum = sum + a;
        }
        NSLog(@"queue 1 = %f",sum);
    });
    
    dispatch_barrier_async(queue, ^{
        double sum = 0;
        for (int a = i; a < n  ; a++)
        {
            sum = sum + a;
        }
        NSLog(@"barrier  = %f",sum);
    });
    
    dispatch_group_async(group, queue, ^{
        double sum = 0;
        for (int a = i; a < n  ; a++)
        {
            sum = sum + a;
        }
        NSLog(@"queue 2 = %f",sum);
    });
    
    
    
    dispatch_group_async(group, queue, ^{
        double sum = 0;
        for (int a = i; a < n  ; a++)
        {
            sum = sum + a;
        }
        NSLog(@"queue 3 = %f",sum);
    });
    
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
       self.displayLabel.text = @"all done";
    });
    
    
//async
//    dispatch_async(queue, ^{
//        double sum = 0;
//        for (int a = i; a < n  ; a++)
//        {
//            sum = sum + a;
////            [self print:a];
//        }
//        dispatch_async(dispatch_get_main_queue(), ^{
//            self.displayLabel.text = [NSString stringWithFormat:@"%f",sum];
//            NSLog(@"is duo xiancheng = %@",[[NSNumber numberWithBool:[NSThread isMultiThreaded]] stringValue]);
//        });
//    });
    
//
    dispatch_async(queue, ^{
        double sum = 0;
        for (int a = i; a < n  ; a++)
        {
            sum = sum + a;
        }
        NSLog(@"barrier queue 1 = %f",sum);
    });
    
    dispatch_async(queue, ^{
        double sum = 0;
        for (int a = i; a < n  ; a++)
        {
            sum = sum + a;
        }
        NSLog(@"barrier  = %f",sum);
    });
    
    dispatch_async(queue, ^{
        double sum = 0;
        for (int a = i; a < n  ; a++)
        {
            sum = sum + a;
        }
        NSLog(@"barrier queue 2 = %f",sum);
    });
    
    
    
    dispatch_async(queue, ^{
        double sum = 0;
        for (int a = i; a < n  ; a++)
        {
            sum = sum + a;
        }
        NSLog(@"barrier queue 3 = %f",sum);
    });
}

– (void)thread3
{
    NSMethodSignature *sig = [self methodSignatureForSelector:@selector(compute:)];
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:sig];
    [invocation setTarget:self];
    [invocation setSelector:@selector(compute:)];
    NSNumber *num = [NSNumber numberWithInt:i];
    [invocation setArgument:&num atIndex:2];
    NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithInvocation:invocation];
    //[[NSInvocationOperation alloc] initWithTarget:self selector:@selector(compute:) object:];
    
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    [queue addOperation:operation];
}

– (void)thread4
{
    NSThread *thread = [[NSThread alloc] initWithTarget:self selector:@selector(compute:) object:[NSNumber numberWithInt:i]];
    [thread start];
}

– (void)thread5
{
    [self performSelectorInBackground:@selector(compute:) withObject:[NSNumber numberWithInt:i]];
}