Re: [Myrinet] (No Subject)

On Sat, 08 Jun 2002 22:14:48  
 Patrick Geoffray wrote:
>Salut Julien,
>
>TOUCHE Julien wrote:
>> with your help, i solve the problem with gm_dma_alloc(), but there is 
>> always a problem of "incompatibles types assignement" with 
>> gm_register_memory()
>
>In the code:
> > *buffer = gm_register_memory(port,
> > 		 
>	buffer,
> > 		 
>	(unsigned int)(size_mem*sizeof(char))
> > 		 
>	);		// DMA transfer register
>
>gm_register_memory return a type gm_status_t. The right code should be :
>
>*buffer = gm_malloc(size_mem*sizeof(char));
>if (gm_register_memory (port, *buffer, (unsigned int)
>       (size_mem * sizeof(char) != GM_SUCCESS)
>{
>   /* something bad happen */
>}
>

so register don't allocate anything, but why use gm_malloc instead 
of gm_dma_malloc ? or can i use both of us ?


>
>> when i use
>  __GM_DMA__ (see end), it compiles but i have the following
>> error:
>> "gm_open: send dropped as requested by the client"
>
>There is many errors in the code. For example:
>* in allocate_gm_buffer, a piece of memory should be allocated before to 
>register it.
>* in allocate_gm_buffer, in the call to gm_register_memory, "buffer" 
>should be "*buffer";
>* in unallocate_gm_buffer, all the "buffer" should be "*buffer";

i've just move the code, and make these 2 functions and i forgotten
to modify this code. sorry ...

>* The value of remote_address is uninitialized.

what do you mean by uninitialized. i could put a NULL at var creation,
but remote_address is to get the distant memory address so it's the
receive which must initialized it.

>* Why do you gm_provide_receive_buffer on "remote_address" before to do 
>a gm_directed_send to the same (uninitialized) address on the other node 
>? gm_directed_send is like a PUT, you only need to register or dma_alloc 
>  on the receiver side the memory you want to write to, and the sender 
>only call gm_directed_send with the virtual address of the *buffer on 
>the receiving side*.

to receive the message from gm_directed_send(), which function must
i use ? gm_receive as for gm_send ?


>* you didn't understand the notion of Sizes in GM. I don't blame you, 
>it's one of the very bad parts of the API, it took me months to (almost) 
>understand what it is. It's like a tag with a relationship with the 
>length of the message, insane. Anyway, think about it like a tag with a 
>value between 8 and 31. The relationship with the length has been 
>relaxed a long time ago actually.

not much clear ;)
for a char[size], which length ?
            size*sizeof(char)
for a int[size] <-> size*sizeof(int) or size ?


>
>> i have also a mpi test which doesn't execute correctly, i don't know 
>> why ? i send a message to another nodes, and it returns but not 
>> modified ...
>
>I looked at it very quickly and the buffer "message" is size_mem 
>characters, but the MPI operations send/recv size_mem integers (MPI_INT).
>
>>   	message = (char *) calloc(size_mem,sizeof(char));
>[...]
>> 		  MPI_Send(message, size_mem , MPI_INT, next, TAG, MPI_COMM_WORLD );
>

for a char[size], the type is what (MPI_CHAR) ?
i don't find much docs on MPI except the one with MPICH but it's not a real guide to programming MPI.
For gm, the myrinet doc is good and the example helps but is not 
sufficient (i don't understand all)(not a real guide programming 
too ;)

but thanks to mailing list, it comes :)

>Patrick
>

---

Thanks
bye

           Julien Touche



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