I spent quite a bit of time looking on how to use the multiprocessing package, but couldn't find anything on how to use it inside a plugin in QGIS. I am developing a plugin that does some optimization for several elements. I would like to parallelize it.

I found a useful link on multi-threading inside a python plugin (http://snorf.net/blog/2013/12/07/multithreading-in-qgis-python-plugins/), but nothing on using the multiprocessing module, which might be easier?

I have been trying with a very basic example. I am only showing the run function from the plugin here:

def run(self):
    """Run method that performs all the real work"""
    # show the dialog
    self.dlg.show()
    
    # Run the dialog event loop
    result = self.dlg.exec_()
    
    # See if OK was pressed and run code
    if result:
        #Get number of cores
        nProcs = mp.cpu_count()
                
        #Start a Process
        p = mp.Pool(nProcs)
        
        #Define function     
            def cube(x):
                return x**3
        
        #Run parallel        
        results = p.map(cube, range(1,7))

When I run this code from the plugin in QGIS, it opens several QGIS windows, which then return errors (can't load layers, etc.). What am I missing? Do I need to start a worker first on another thread and then use multiprocessing there? Or would we use another function from multiprocessing?

Please let me know if the question needs edits. I am working under windows 7, using QGIS 2.10.

Thanks,

I spent quite a bit of time looking on how to use the multiprocessing package, but couldn't find anything on how to use it inside a plugin in QGIS. I am developing a plugin that does some optimization for several elements. I would like to parallelize it.

I found a useful link on multi-threading inside a python plugin (http://snorf.net/blog/2013/12/07/multithreading-in-qgis-python-plugins/), but nothing on using the multiprocessing module, which might be easier?

I have been trying with a very basic example. I am only showing the run function from the plugin here:

def run(self):
    """Run method that performs all the real work"""
    # show the dialog
    self.dlg.show()
    
    # Run the dialog event loop
    result = self.dlg.exec_()
    
    # See if OK was pressed and run code
    if result:
        #Get number of cores
        nProcs = mp.cpu_count()
                
        #Start a Process
        p = mp.Pool(nProcs)
        
        #Define function     
            def cube(x):
                return x**3
        
        #Run parallel        
        results = p.map(cube, range(1,7))

When I run this code from the plugin in QGIS, it opens several QGIS windows, which then return errors (can't load layers, etc.).

What am I missing? 

Do I need to start a worker first on another thread and then use multiprocessing there? 

Or would we use another function from multiprocessing?

I am working under windows 7, using QGIS 2.10.

I spent quite a bit of time looking on how to use the multiprocessing package, but couldn't find anything on how to use it inside a puglin in Qgis. I am developing a plugin that does some optimization for several elements. I would like to parallelize it.

I found a useful link on multi-threading inside a python plugin (http://snorf.net/blog/2013/12/07/multithreading-in-qgis-python-plugins/), but nothing on using the multiprocessing module, which might be easier?

I have been trying with a very basic example. I am only showing the run function from the plugin here:

def run(self):
    """Run method that performs all the real work"""
    # show the dialog
    self.dlg.show()
    
    # Run the dialog event loop
    result = self.dlg.exec_()
    
    # See if OK was pressed and run code
    if result:
        #Get number of cores
        nProcs = mp.cpu_count()
                
        #Start a Process
        p = mp.Pool(nProcs)
        
        #Define function     
            def cube(x):
                return x**3
        
        #Run parallel        
        results = p.map(cube, range(1,7))

When I run this code from the plugin in Qgis, it opens several Qgis windows, which then return errors (can't load layers, etc.). What am I missing? Do I need to start a worker first on another thread and then use multiprocessing there? Or whould we use another function from multiprocessing?

Please let me know if the question needs edits. I am working unser windows 7, using Qgis 2.10.

Thanks,

I spent quite a bit of time looking on how to use the multiprocessing package, but couldn't find anything on how to use it inside a plugin in QGIS. I am developing a plugin that does some optimization for several elements. I would like to parallelize it.

I found a useful link on multi-threading inside a python plugin (http://snorf.net/blog/2013/12/07/multithreading-in-qgis-python-plugins/), but nothing on using the multiprocessing module, which might be easier?

I have been trying with a very basic example. I am only showing the run function from the plugin here:

def run(self):
    """Run method that performs all the real work"""
    # show the dialog
    self.dlg.show()
    
    # Run the dialog event loop
    result = self.dlg.exec_()
    
    # See if OK was pressed and run code
    if result:
        #Get number of cores
        nProcs = mp.cpu_count()
                
        #Start a Process
        p = mp.Pool(nProcs)
        
        #Define function     
            def cube(x):
                return x**3
        
        #Run parallel        
        results = p.map(cube, range(1,7))

When I run this code from the plugin in QGIS, it opens several QGIS windows, which then return errors (can't load layers, etc.). What am I missing? Do I need to start a worker first on another thread and then use multiprocessing there? Or would we use another function from multiprocessing?

Please let me know if the question needs edits. I am working under windows 7, using QGIS 2.10.

Thanks,