[Openmp-dev] [Openmp-commits] Intel OpenMP Runtime & LLVM : RUNTIME FUNCTION (newly written) CALL gets " Undefined Reference"
Cownie, James H via Openmp-dev
openmp-dev at lists.llvm.org
Wed Jan 20 02:07:09 PST 2016
At a guess you’re not linking against the runtime you have modified.
Check exactly which shared library is being linked, and then use nm on it to see what symbols it contains.
As a second, stylistic, issue: please don’t name your new, non-standard function “omp_anything”. Such names should be reserved for functions from the OpenMP standard. Historically other, non-standard, entrypoints to the runtime have used the “kmp_” prefix. Either use that, or choose your own, but having non-standard functionality appear to be standard is asking for trouble.
-- Jim
James Cownie <james.h.cownie at intel.com>
SSG/DPD/TCAR (Technical Computing, Analyzers and Runtimes)
Tel: +44 117 9071438
From: Openmp-commits [mailto:openmp-commits-bounces at lists.llvm.org] On Behalf Of Rezaul Karim Raju via Openmp-commits
Sent: Wednesday, January 20, 2016 3:33 AM
To: openmp-dev at lists.llvm.org; openmp-commits at lists.llvm.org
Subject: Re: [Openmp-commits] [Openmp-dev] Intel OpenMP Runtime & LLVM : RUNTIME FUNCTION (newly written) CALL gets " Undefined Reference"
Hello everyone,
I was writing a new runtime routine to integrate with intel openMP runtime. My function call is pretty like the calling of, "omp_set_num_threads(4);"
omp_set_my_threads(8);
omp_set_data_bind(&bindvariable);
my goal here is to set/provide (to runtime) a integer value and an address location through runtime routine call.
What I did:
I have made a shadow copy like the omp_set_num_thread() function implementation; it generates the function prototype as below in the omp.h header file:
extern void __KAI_KMPC_CONVENTION omp_set_num_threads (int);
extern void __KAI_KMPC_CONVENTION omp_set_data_bind (void *);
extern void __KAI_KMPC_CONVENTION omp_set_my_threads (int);
and in my program I am calling like:
int main(){
....
omp_set_num_threads(4);
omp_set_my_threads(8);
omp_set_data_bind(&bindvariable);
#pragma omp parallel
{
---
}
}
Compile with CLANG (LLVM) the IR code generates the function call as: call void @omp_set_my_threads(i32 8)
but while I am going to compile it gives me the error as:
/tmp/XXXa.o: In function `main':
XXXa.c:(.text+0x403): undefined reference to `omp_set_my_threads'
clang-3.5: error: linker command failed with exit code 1
CAN YOU PLEASE COMMENT WHAT I AM MISSING HERE ..?
thank you very much in advance..!!
- Raju
On Tue, Dec 15, 2015 at 11:02 AM, Churbanov, Andrey <Andrey.Churbanov at intel.com<mailto:Andrey.Churbanov at intel.com>> wrote:
Hello,
If you print information from __kmp_task_alloc() function, you cannot find your data in the structures.
The reason is that this routine only allocates space requested by the compiler and initializes its own runtime-related info, and if you examine the space allocated for shareds you can only find uninitialized memory there.
The addresses of shared variables are put into allocated memory by the compiler later, AFTER the __kmp_task_alloc() call. E.g. the array of shareds should already be initialized in the __kmp_omp_task() call. But I doubt you can rely on particular location of any shared variable in the array of shareds, it is compiler’s decision where to place your particular variable’s address, and it may or may not be the first in the array of shareds. E.g. compiler can insert its own auxiliary data before user’s data.
Regards,
Andrey
From: Openmp-dev [mailto:openmp-dev-bounces at lists.llvm.org<mailto:openmp-dev-bounces at lists.llvm.org>] On Behalf Of Rezaul Karim Raju via Openmp-dev
Sent: Tuesday, December 15, 2015 8:47 AM
To: openmp-dev at lists.llvm.org<mailto:openmp-dev at lists.llvm.org>; openmp-commits at lists.llvm.org<mailto:openmp-commits at lists.llvm.org>
Subject: [Openmp-dev] Intel OpenMP Runtime & LLVM [kmp_tasking.c]: Problem to access SHARED VARIABLE DATA LOCATION
Dear concern,
Please consider the source code(openmp c code) snippet as below:
--- code snippet ---
int a1, b1, c1, N;
Initially address of a1:= 0x7fff9bd58304
omp_set_num_threads(2);
#pragma omp parallel
{
#pragma omp single
{
// task one: a1=b1+c1;
#pragma omp task shared(a1) firstprivate(b1,c1)
{
a1 = a1 + b1 + c1;
}
}
}
In the above openMP code task construct contains shared variable (a1), I AM INTERESTED TO FIND THE SHARED VARIABLE OF TASK DATA IN RUNTIME TASK ALLOCATION.
I am looking into the source code of Intel OpenMP Runtime, my openmp code is compiled with LLVM. In the LLVM IR, @__kmpc_omp_task_alloc( ...) calls runtime function kmp_task_alloc(), source code is here: under the <src> directory, Kmp_tasking.c
I am trying to access the "shared variable data location for a task" which is as below:
kmp_task_t *
__kmp_task_alloc(...){
kmp_task_t *task;
kmp_taskdata_t *taskdata;
// Calculate shared structure offset including padding after kmp_task_t struct
// to align pointers in shared struct
shareds_offset = sizeof( kmp_taskdata_t ) + sizeof_kmp_task_t;
shareds_offset = __kmp_round_up_to_val( shareds_offset, sizeof( void * ));
// Avoid double allocation here by combining shareds with taskdata
#if USE_FAST_MEMORY
taskdata = (kmp_taskdata_t *) __kmp_fast_allocate( thread, shareds_offset + sizeof_shareds );
#else /* ! USE_FAST_MEMORY */
taskdata = (kmp_taskdata_t *) __kmp_thread_malloc( thread, shareds_offset + sizeof_shareds );
#endif /* USE_FAST_MEMORY */
task = KMP_TASKDATA_TO_TASK(taskdata);
if (sizeof_shareds > 0) {
// Avoid double allocation here by combining shareds with taskdata
task->shareds = & ((char *) taskdata)[ shareds_offset ];
printf("task->shareds address original:= %p address of pointer it points to := %p\n", & ((char *) taskdata)[ shareds_offset ], *task->shareds);
}
}
here,
typedef struct kmp_task { /* GEH: Shouldn't this be aligned somehow? */
void * shareds; /**< pointer to block of pointers to shared vars */
}
But, task->shareds = & ((char *) taskdata)[ shareds_offset ]; which is a pointer to block of pointers to shared variables, if I print the shared variable pointing address(which should be the address of a1:= 0x7fff9bd58304)
IT PRINTS DIFFERENT ADDRESS: <0x1fe0ef0>
NEED TO GET THE ADDRESS OF TASK'S SHARED VARIABLE ADDRESS FROM RUNTIME.
appreciate your comment and help. Thanking you.
------------------------
RaJu, Rezaul Karim
Graduate Student (PhD) | Computer Science | University of Houston
Research in High Performance Computing Tools
Houston, Texas-77004
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Graduate Student (PhD) | Computer Science | University of Houston
Research in High Performance Computing Tools
Houston, Texas-77004
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