[Starpu-devel] Pointer arithmetic and OpenCL

[Nathalie Furmento <nathalie.furmento@labri.fr>]

As OpenCL does not allow to perform pointer arithmetics on a cl_mem 
object, it is necessary to keep  the original pointer and the offset 
when splitting data in StarPU.

Here a patch (approved by Cédric himself ;)) fixing the vector interface 
in that regard. Comments welcome!

Nathalie

-----------------------------------------------------------------------------------------------------------------
Index: include/starpu-data-interfaces.h
===================================================================
--- include/starpu-data-interfaces.h    (revision 1822)
+++ include/starpu-data-interfaces.h    (working copy)
@@ -86,6 +86,8 @@
/* vector interface for contiguous (non-strided) buffers */
typedef struct starpu_vector_interface_s {
       uintptr_t ptr;
+        uintptr_t dev_handle;
+        size_t offset;
       uint32_t nx;
       size_t elemsize;
} starpu_vector_interface_t;
Index: src/datawizard/interfaces/vector_interface.c
===================================================================
--- src/datawizard/interfaces/vector_interface.c        (revision 1822)
+++ src/datawizard/interfaces/vector_interface.c        (working copy)
@@ -87,13 +87,16 @@

               if (node == home_node) {
                       local_interface->ptr = vector_interface->ptr;
+                        local_interface->dev_handle = 
vector_interface->dev_handle;
               }
               else {
                       local_interface->ptr = 0;
+                        local_interface->dev_handle = 0;
               }

               local_interface->nx = vector_interface->nx;
               local_interface->elemsize = vector_interface->elemsize;
+                local_interface->offset = vector_interface->offset;
       }
}

@@ -116,7 +119,9 @@
       starpu_vector_interface_t vector = {
               .ptr = ptr,
               .nx = nx,
-               .elemsize = elemsize
+               .elemsize = elemsize,
+                .dev_handle = ptr,
+                .offset = 0
       };     

       _starpu_register_data_handle(handleptr, home_node, &vector, 
&interface_vector_ops);
@@ -228,6 +233,8 @@

       /* update the data properly in consequence */
       interface->ptr = addr;
+        interface->dev_handle = addr;
+        interface->offset = 0;
      
       return allocated_memory;
}

Index: src/datawizard/interfaces/vector_filters.c
===================================================================
--- src/datawizard/interfaces/vector_filters.c  (revision 1822)
+++ src/datawizard/interfaces/vector_filters.c  (working copy)
@@ -28,6 +28,7 @@

       uint32_t nx = vector_root->nx;
       size_t elemsize = vector_root->elemsize;
+        uintptr_t dev_handle = vector_root->dev_handle;

       /* we will have arg chunks */
       nchunks = STARPU_MIN(nx, arg);
@@ -62,6 +63,8 @@
                                       
starpu_data_get_interface_on_node(root_handle, node);

                               local->ptr = local_root->ptr + offset;
+                                local->dev_handle = local_root->dev_handle;
+                                local->offset = local_root->offset + 
offset;
                       }
               }
       }
@@ -77,6 +80,7 @@

       uint32_t nx = vector_root->nx;
       size_t elemsize = vector_root->elemsize;
+        uintptr_t dev_handle = vector_root->dev_handle;

       /* first allocate the children data_state */
       starpu_data_create_children(root_handle, 2, root_handle->ops);
@@ -100,6 +104,8 @@
                               
starpu_data_get_interface_on_node(root_handle, node);

                       local->ptr = local_root->ptr;
+                        local->offset = local_root->offset;
+                        local->dev_handle = local_root->dev_handle;
               }
       }

@@ -119,6 +125,8 @@
                               
starpu_data_get_interface_on_node(root_handle, node);

                       local->ptr = local_root->ptr + 
length_first*elemsize;
+                        local->offset = local_root->offset + 
length_first*elemsize;
+                        local->dev_handle = local_root->dev_handle;
               }
       }
}
@@ -161,6 +169,8 @@
                                       
starpu_data_get_interface_on_node(root_handle, node);

                               local->ptr = local_root->ptr + 
current_pos*elemsize;
+                                local->offset = local_root->offset + 
current_pos*elemsize;
+                                local->dev_handle = local_root->dev_handle;