[OMPI devel] MPI_T and coll/tuned module

[Gilles Gouaillardet]

Folks,

i was thinking of using the MPI_T interface in order to try within the 
same MPI test program *all* the available algo of a given collective.


That cannot currently be done because the mca parameter is registered with

{flag=0, scope=MCA_BASE_VAR_SCOPE_READONLY}


i made a proof of concept by changing this to

{flag=MCA_BASE_VAR_FLAG_SETTABLE, scope=MCA_VAR_SCOPE_ALL}

(see the inline patch below)


strictly speaking, it does not work since the updated values are used 
next time a communicator is created.

for example, changing a value on MPI_COMM_WORLD has no effect,

but changing a value, MPI_Comm_dup(MPI_COMM_WORLD) and using the dup'ed 
communicator works.

btw, i guess any communicator could be used to set the value.


as far as i am concerned, that is good enough for me


any objections to make some coll/tuned parameters writable by MPI_T ?

if no, did i implement it correctly ?


Cheers,


Gilles


here is the function that sets a value :

int setValue_int_comm(int index, MPI_Comm comm, int *val) {
  int err,count;
  MPI_T_cvar_handle handle;
  /* This example assumes that the variable index */
  /* can be bound to a communicator */
err=MPI_T_cvar_handle_alloc(index,&comm,&handle,&count);
  if (err!=MPI_SUCCESS) return err;
  /* The following assumes that the variable is */
  /* represented by a single integer */
  err=MPI_T_cvar_write(handle,val);
  if (err!=MPI_SUCCESS) return err;
  err=MPI_T_cvar_handle_free(&handle);
  return err;
}

and here is the proof of concept

diff --git a/ompi/mca/coll/tuned/coll_tuned_bcast_decision.c 
b/ompi/mca/coll/tuned/coll_tuned_bcast_decision.c
index 81345b2..31ca217 100644
--- a/ompi/mca/coll/tuned/coll_tuned_bcast_decision.c
+++ b/ompi/mca/coll/tuned/coll_tuned_bcast_decision.c
@@ -76,9 +76,9 @@ int ompi_coll_tuned_bcast_intra_check_forced_init 
(coll_tuned_force_algorithm_mc
mca_base_component_var_register(&mca_coll_tuned_component.super.collm_version,
                                         "bcast_algorithm",
                                         "Which bcast algorithm is 
used. Can be locked down to choice of: 0 ignore, 1 basic linear, 2 
chain, 3: pipeline, 4: split binary tree, 5: binary tree, 6: binomial 
tree.",
-                                        MCA_BASE_VAR_TYPE_INT, 
new_enum, 0, 0,
+                                        MCA_BASE_VAR_TYPE_INT, 
new_enum, 0, MCA_BASE_VAR_FLAG_SETTABLE,
                                         OPAL_INFO_LVL_5,
- MCA_BASE_VAR_SCOPE_READONLY,
+                                        MCA_BASE_VAR_SCOPE_ALL,
&coll_tuned_bcast_forced_algorithm);
     OBJ_RELEASE(new_enum);
     if (mca_param_indices->algorithm_param_index < 0) {
diff --git a/ompi/mca/coll/tuned/coll_tuned_component.c 
b/ompi/mca/coll/tuned/coll_tuned_component.c
index 9756359..ea389fd 100644
--- a/ompi/mca/coll/tuned/coll_tuned_component.c
+++ b/ompi/mca/coll/tuned/coll_tuned_component.c
@@ -164,9 +164,9 @@ static int tuned_register(void)
     (void) 
mca_base_component_var_register(&mca_coll_tuned_component.super.collm_version,
                                            "use_dynamic_rules",
                                            "Switch used to decide if 
we use static (compiled/if statements) or dynamic (built at runtime) 
decision function rules",
- MCA_BASE_VAR_TYPE_BOOL, NULL, 0, 0,
+ MCA_BASE_VAR_TYPE_BOOL, NULL, 0, MCA_BASE_VAR_FLAG_SETTABLE,
                                            OPAL_INFO_LVL_6,
- MCA_BASE_VAR_SCOPE_READONLY,
+ MCA_BASE_VAR_SCOPE_ALL,
&ompi_coll_tuned_use_dynamic_rules);

     ompi_coll_tuned_dynamic_rules_filename = NULL;