[Omp] Working with threadprivate elements of structs

[Shah, Sanjiv]

Clay,
 
Yes, this should be sufficient.  The only other thing to worry about is
to guarantee persistence of the threadprivate's across multiple parallel
regions.  If you disable omp_dynamic (as Andrey suggested) and keep the
number of threads in all the regions the same, you will have this
guarantee.
 
Sanjiv
 

-- 
Sanjiv, 217-403-4244 

 

  _____  

From: Breshears, Clay 
Sent: Tuesday, January 13, 2004 10:56 AM
To: Shah, Sanjiv; 'omp at openmp.org'
Subject: RE: [Omp] Working with threadprivate elements of structs


Sanjiv -
 
Okay, that make sense.  If I initialized the static_ltree with a static
initializer, used a NULL in the l_desc initialization, and then stored
the address of static_ltree in l_desc within a parallel region, would
this set up the correct address and threadprivates that I need? 
 
Example code:
 
ct_data static_ltree[100] = { {0,0} };  //init one element to force use?

#pragma omp threadprivate (static_ltree)

typedef struct tree_desc { 
   ct_data *tree; 
   int max_length; 
   int max_code; 
} tree_desc; 

tree_desc l_desc = {NULL, MAX_LEN, 0}; 

#pragma omp threadprivate (l_desc)

 

#pragma omp parallel   
   l_desc.tree = static_ltree;   //threadprivate address into
threadprivate?


	-----Original Message-----
	From: Shah, Sanjiv 
	Sent: Friday, January 09, 2004 6:12 PM
	To: Breshears, Clay; omp at openmp.org
	Subject: RE: [Omp] Working with threadprivate elements of
structs
	
	
	Clay,
	 
	Addresses of threadprivate objects are not constant, so as soon
as you make static_ltree threadprivate, you will not be able to use it
in the structure initialization for l_desc.  You will have to initialize
the tree field with NULL and then use a dummy parallel region, as you
suggest, to set up the correct linkages.  The code should be just a
simple assignment in the parallel region.
	 
	Sanjiv
	 

	-- 
	Sanjiv, 217-403-4244 

	 

  _____  

	From: Omp-bounces at openmp.org [mailto:Omp-bounces at openmp.org] On
Behalf Of Breshears, Clay
	Sent: Friday, January 09, 2004 5:45 PM
	To: omp at openmp.org
	Subject: [Omp] Working with threadprivate elements of structs
	
	


	I need to have a threadprivate array that is pointed to by a
threadprivate struct.  How do I declare and initialize these so they all
refer to the correct versions?

	In a C code, I have an array that needs to be threadprivate.
The original serial code also includes a struct (used as a descriptor to
carry additional information about the array and its contents) that is
also used as a parameter to some function calls.  The fields of the
descriptor instances are statically initialized at declaration time.
For example, the serial code looks something like:

	ct_data static_ltree[100]; 

	typedef struct tree_desc { 
	   ct_data *tree; 
	   int max_length; 
	   int max_code; 
	} tree_desc; 

	tree_desc l_desc = {static_ltree, MAX_LEN, 0}; 

	If I put in pragmas to set static_ltree and l_desc to be
threadprivate, how can I guarantee that each thread's copy of
static_ltree will be pointed to by that same thread's copy of l_desc?
Do I need to use a "dummy" parallel region to access static_ltree and
initialize l_desc in parallel to make sure the desired linkage occurs?
Does the static initialization of l_desc suffice to hook things up
correctly?  Is there a better or simpler way?

	Thanks in advance for any help or advice. 

	                                                clay 
	-- 
	Clay Breshears   
	Parallel Applications Engineer 
	KAI Software Labs, a division of Intel Americas, Inc.   
	phone: 217-403-4206  fax: 217-403-4399 

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