diff --git a/README.md b/README.md
index fba05c2..47f1204 100644
--- a/README.md
+++ b/README.md
@@ -253,18 +253,18 @@ You have to use events for that, you will modify both the C and YAML file.
 ```bash
   diff ex5.h5dump <(h5dump ex5*.h5)
 ```
-
-
 ### Ex6. Simplifying the code
 
 As you can notice, the %PDI code is quite redundant.
 In this exercise, you will use `::PDI_expose` and `::PDI_multi_expose` to
 simplify the code while keeping the exact same behaviour.
 For once, there is no need to modify the YAML file here, you only need to modify
-the C file in this exercise.
+the C file. Moreover, This exercise will be launched in sequential to facilitate the comparison between logs.
 
 * Examine the source code, compile it and run it.
 
+\remark At the end of the iteration loop, a new event `finalization` is added.
+
 There are lots of matched `::PDI_share`/`::PDI_reclaim` in the code.
 
 * Replace these by `::PDI_expose` that is the exact equivalent of a
@@ -276,13 +276,17 @@ This case is however handled by `::PDI_multi_expose` call that exposes all data,
 then triggers an event and finally does all the reclaim in reverse order.
 
 * Replace the remaining `::PDI_share`/`::PDI_reclaim` by `::PDI_expose`s and
-  `::PDI_multi_expose`s and ensure that your code keeps the exact same behaviour
-  by comparing its trace to `ex6.log` (only the lines matching `[Trace-plugin]`
-  have been kept). You can easily check if the files are the same by running:
+  `::PDI_multi_expose`s and ensure that your code keeps the exact same behaviour as in previous exercise by comparing its trace to `ex6.log`
+  (only the lines matching `[Trace-plugin]` have been kept). Using the previous section [Execution with storage of the log](#execution-with-storage-of-the-log),
+  run  this exercise in saving the output log in the `ex6.result.log`.
+  After that you can easily check if the files are the same by running:
 ```bash
   diff ex6.log <(grep Trace-plugin ex6.result.log)
 ```
 
+In summary:\n 
+  1. `::PDI_expose` is equivalent to `::PDI_share` + `::PDI_reclaim` \n 
+  2. `::PDI_multi_expose` is equivalent to `::PDI_share` + `::PDI_event` + `::PDI_reclaim`\n 
 
 ### Ex7. Writing a selection
 
diff --git a/ex6.c b/ex6.c
index 020071b..5b6f6f3 100644
--- a/ex6.c
+++ b/ex6.c
@@ -29,7 +29,6 @@
 #include <time.h>
 
 #include <paraconf.h>
-// load the PDI header
 #include <pdi.h>
 
 /// size of the local data as [HEIGHT, WIDTH] including ghosts & boundary constants
@@ -44,13 +43,32 @@ int pcoord[2];
 /// the alpha coefficient used in the computation
 double alpha;
 
+double L=1.0;
+double source1[4]={0.4, 0.4, 0.2, 100};
+double source2[4]={0.7, 0.8, 0.1, 200};
+
 /** Initialize the data all to 0 except for the left border (XX==0) initialized to 1 million
  * \param[out] dat the local data to initialize
  */
 void init(double dat[dsize[0]][dsize[1]])
 {
 	for (int yy=0; yy<dsize[0]; ++yy)  for (int xx=0; xx<dsize[1]; ++xx)  dat[yy][xx] = 0;
-	if ( pcoord[1] == 0 ) for (int yy=0; yy<dsize[0]; ++yy)  dat[yy][0] = 1000000;
+	double dy = L / ((dsize[0]-2) *psize[0]) ;
+	double dx = L / ((dsize[1]-2) *psize[1]) ;
+
+	double cpos_x,cpos_y;
+	for(int yy=0; yy<dsize[0];++yy) {
+		cpos_y=(yy+pcoord[0]*(dsize[0]-2))*dy-0.5*dy;
+		for(int xx=0; xx<dsize[1];++xx) {
+			cpos_x=(xx+pcoord[1]*(dsize[1]-2))*dx-0.5*dx;
+			if((cpos_y-source1[0])*(cpos_y-source1[0]) + (cpos_x-source1[1])*(cpos_x-source1[1]) <= source1[2]*source1[2]) {
+				dat[yy][xx] = source1[3];
+			}
+			if((cpos_y-source2[0])*(cpos_y-source2[0]) + (cpos_x-source2[1])*(cpos_x-source2[1]) <= source2[2]*source2[2]) {
+				dat[yy][xx] = source2[3];
+			}
+		}
+	}
 }
 
 /** Compute the values at the next time-step based on the values at the current time-step
@@ -60,21 +78,15 @@ void init(double dat[dsize[0]][dsize[1]])
 void iter(double cur[dsize[0]][dsize[1]], double next[dsize[0]][dsize[1]])
 {
 	int xx, yy;
-	for (xx=0; xx<dsize[1]; ++xx) next[0][xx] = cur[0][xx];
 	for (yy=1; yy<dsize[0]-1; ++yy) {
-		next[yy][0] = cur[yy][0];
 		for (xx=1; xx<dsize[1]-1; ++xx) {
-			next[yy][xx] =
-					  (1.-4.*alpha) * cur[yy][xx]
-					+        alpha  * (   cur[yy][xx-1]
-					                    + cur[yy][xx+1]
-					                    + cur[yy-1][xx]
-					                    + cur[yy+1][xx]
-					                  ); 
+			next[yy][xx] = (1.-4.*alpha) * cur[yy][xx]
+					             +alpha  * ( cur[yy][xx-1]
+					                       + cur[yy][xx+1]
+					                       + cur[yy-1][xx]
+					                       + cur[yy+1][xx]); 
 		}
-		next[yy][dsize[1]-1] = cur[yy][dsize[1]-1];
 	}
-	for (xx=0; xx<dsize[1]; ++xx) next[dsize[0]-1][xx] = cur[dsize[0]-1][xx];
 }
 
 /** Exchanges ghost values with neighbours
@@ -162,7 +174,7 @@ int main( int argc, char* argv[] )
 	dsize[1] = global_size[1]/psize[1] + 2;
 	
 	// create a 2D Cartesian MPI communicator & get our coordinate (rank) in it
-	int cart_period[2] = { 0, 0 };
+	int cart_period[2] = { 1, 1 };
 	MPI_Comm cart_comm; MPI_Cart_create(main_comm, 2, psize, cart_period, 1, &cart_comm);
 	MPI_Cart_coords(cart_comm, pcoord_1d, 2, pcoord);
 	
@@ -178,20 +190,20 @@ int main( int argc, char* argv[] )
 	int ii=0;
 	
 	// share useful configuration bits with PDI
-	PDI_share("ii",         &ii,    PDI_OUT);
-	PDI_reclaim("ii");
+	//*** use PDI_expose to replace PDI_share + reclaim
+	//...
 	PDI_share("pcoord",     pcoord, PDI_OUT);
 	PDI_reclaim("pcoord");
 	PDI_share("dsize",      dsize,  PDI_OUT);
 	PDI_reclaim("dsize");
 	PDI_share("psize",      psize,  PDI_OUT);
 	PDI_reclaim("psize");
-	PDI_share("main_field", cur,    PDI_OUT);
-	PDI_reclaim("main_field");
 	
 	// the main loop
 	for (; ii<10; ++ii) {
 		// share the loop counter & main field at each iteration
+		//*** use PDI_multi_expose to replace PDI_share + event + reclaim
+		//...
 		PDI_share("ii",         &ii, PDI_OUT);
 		PDI_share("main_field", cur, PDI_OUT);
 		PDI_event("loop");
@@ -208,11 +220,13 @@ int main( int argc, char* argv[] )
 		double (*tmp)[dsize[1]] = cur; cur = next; next = tmp;
 	}
 	// finally share the main field as well as the loop counter after the loop
-	PDI_share("main_field", cur, PDI_OUT);
+	//*** use PDI_multi_expose to replace PDI_share + event + reclaim
+	//...
 	PDI_share("ii",         &ii, PDI_OUT);
+	PDI_share("main_field", cur, PDI_OUT);
 	PDI_event("finalization");
-	PDI_reclaim("ii");
 	PDI_reclaim("main_field");
+	PDI_reclaim("ii");
 	
 	// finalize PDI
 	PDI_finalize();
@@ -230,3 +244,4 @@ int main( int argc, char* argv[] )
 	fprintf(stderr, "[%d] SUCCESS\n", pcoord_1d);
 	return EXIT_SUCCESS;
 }
+
diff --git a/ex6.log b/ex6.log
index 1d498c6..d0aecc6 100644
--- a/ex6.log
+++ b/ex6.log
@@ -1,15 +1,46 @@
 [PDI][Trace-plugin] *** info: Welcome!
 [PDI][Trace-plugin] *** info: !!!                            named event: initialization
-[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: ii
-[PDI][Trace-plugin] *** info: <<= data stop being available in the store: ii
 [PDI][Trace-plugin] *** info: =>>   data becoming available in the store: pcoord
 [PDI][Trace-plugin] *** info: <<= data stop being available in the store: pcoord
 [PDI][Trace-plugin] *** info: =>>   data becoming available in the store: dsize
 [PDI][Trace-plugin] *** info: <<= data stop being available in the store: dsize
 [PDI][Trace-plugin] *** info: =>>   data becoming available in the store: psize
 [PDI][Trace-plugin] *** info: <<= data stop being available in the store: psize
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: main_field
+[PDI][Trace-plugin] *** info: !!!                            named event: loop
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: main_field
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: main_field
+[PDI][Trace-plugin] *** info: !!!                            named event: loop
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: main_field
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: ii
 [PDI][Trace-plugin] *** info: =>>   data becoming available in the store: main_field
+[PDI][Trace-plugin] *** info: !!!                            named event: loop
 [PDI][Trace-plugin] *** info: <<= data stop being available in the store: main_field
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: main_field
+[PDI][Trace-plugin] *** info: !!!                            named event: loop
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: main_field
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: main_field
+[PDI][Trace-plugin] *** info: !!!                            named event: loop
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: main_field
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: main_field
+[PDI][Trace-plugin] *** info: !!!                            named event: loop
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: main_field
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: ii
+[PDI][Trace-plugin] *** info: =>>   data becoming available in the store: main_field
+[PDI][Trace-plugin] *** info: !!!                            named event: loop
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: main_field
+[PDI][Trace-plugin] *** info: <<= data stop being available in the store: ii
 [PDI][Trace-plugin] *** info: =>>   data becoming available in the store: ii
 [PDI][Trace-plugin] *** info: =>>   data becoming available in the store: main_field
 [PDI][Trace-plugin] *** info: !!!                            named event: loop
diff --git a/ex6.yml b/ex6.yml
index fb85810..3c3622e 100644
--- a/ex6.yml
+++ b/ex6.yml
@@ -16,3 +16,14 @@ pdi:
   plugins:
     trace:
       logging: { pattern: '[PDI][%n-plugin] *** %l: %v' }
+    decl_hdf5:
+      - file: ex5-meta${pcoord[0]}x${pcoord[1]}.h5
+        write: [ dsize, psize ]
+      - file: ex5-data${pcoord[0]}x${pcoord[1]}.h5
+        on_event: loop
+        when: '$ii>0 & $ii<3' 
+        write:
+          ii:
+            dataset: 'iter${ii}/ii' 
+          main_field:
+            dataset: 'iter${ii}/main_field'
diff --git a/solutions/ex6.c b/solutions/ex6.c
index 1272adc..7e3aa02 100644
--- a/solutions/ex6.c
+++ b/solutions/ex6.c
@@ -29,7 +29,6 @@
 #include <time.h>
 
 #include <paraconf.h>
-// load the PDI header
 #include <pdi.h>
 
 /// size of the local data as [HEIGHT, WIDTH] including ghosts & boundary constants
@@ -44,13 +43,32 @@ int pcoord[2];
 /// the alpha coefficient used in the computation
 double alpha;
 
+double L=1.0;
+double source1[4]={0.4, 0.4, 0.2, 100};
+double source2[4]={0.7, 0.8, 0.1, 200};
+
 /** Initialize the data all to 0 except for the left border (XX==0) initialized to 1 million
  * \param[out] dat the local data to initialize
  */
 void init(double dat[dsize[0]][dsize[1]])
 {
 	for (int yy=0; yy<dsize[0]; ++yy)  for (int xx=0; xx<dsize[1]; ++xx)  dat[yy][xx] = 0;
-	if ( pcoord[1] == 0 ) for (int yy=0; yy<dsize[0]; ++yy)  dat[yy][0] = 1000000;
+	double dy = L / ((dsize[0]-2) *psize[0]) ;
+	double dx = L / ((dsize[1]-2) *psize[1]) ;
+
+	double cpos_x,cpos_y;
+	for(int yy=0; yy<dsize[0];++yy) {
+		cpos_y=(yy+pcoord[0]*(dsize[0]-2))*dy-0.5*dy;
+		for(int xx=0; xx<dsize[1];++xx) {
+			cpos_x=(xx+pcoord[1]*(dsize[1]-2))*dx-0.5*dx;
+			if((cpos_y-source1[0])*(cpos_y-source1[0]) + (cpos_x-source1[1])*(cpos_x-source1[1]) <= source1[2]*source1[2]) {
+				dat[yy][xx] = source1[3];
+			}
+			if((cpos_y-source2[0])*(cpos_y-source2[0]) + (cpos_x-source2[1])*(cpos_x-source2[1]) <= source2[2]*source2[2]) {
+				dat[yy][xx] = source2[3];
+			}
+		}
+	}
 }
 
 /** Compute the values at the next time-step based on the values at the current time-step
@@ -60,21 +78,15 @@ void init(double dat[dsize[0]][dsize[1]])
 void iter(double cur[dsize[0]][dsize[1]], double next[dsize[0]][dsize[1]])
 {
 	int xx, yy;
-	for (xx=0; xx<dsize[1]; ++xx) next[0][xx] = cur[0][xx];
 	for (yy=1; yy<dsize[0]-1; ++yy) {
-		next[yy][0] = cur[yy][0];
 		for (xx=1; xx<dsize[1]-1; ++xx) {
-			next[yy][xx] =
-					  (1.-4.*alpha) * cur[yy][xx]
-					+        alpha  * (   cur[yy][xx-1]
-					                    + cur[yy][xx+1]
-					                    + cur[yy-1][xx]
-					                    + cur[yy+1][xx]
-					                  ); 
+			next[yy][xx] = (1.-4.*alpha) * cur[yy][xx]
+					             +alpha  * ( cur[yy][xx-1]
+					                       + cur[yy][xx+1]
+					                       + cur[yy-1][xx]
+					                       + cur[yy+1][xx]); 
 		}
-		next[yy][dsize[1]-1] = cur[yy][dsize[1]-1];
 	}
-	for (xx=0; xx<dsize[1]; ++xx) next[dsize[0]-1][xx] = cur[dsize[0]-1][xx];
 }
 
 /** Exchanges ghost values with neighbours
@@ -162,7 +174,7 @@ int main( int argc, char* argv[] )
 	dsize[1] = global_size[1]/psize[1] + 2;
 	
 	// create a 2D Cartesian MPI communicator & get our coordinate (rank) in it
-	int cart_period[2] = { 0, 0 };
+	int cart_period[2] = { 1, 1 };
 	MPI_Comm cart_comm; MPI_Cart_create(main_comm, 2, psize, cart_period, 1, &cart_comm);
 	MPI_Cart_coords(cart_comm, pcoord_1d, 2, pcoord);
 	
@@ -178,15 +190,15 @@ int main( int argc, char* argv[] )
 	int ii=0;
 	
 	// share useful configuration bits with PDI
-	PDI_expose("ii",         &ii,    PDI_OUT);
+	//*** use PDI_expose to replace PDI_share + reclaim
 	PDI_expose("pcoord",     pcoord, PDI_OUT);
 	PDI_expose("dsize",      dsize,  PDI_OUT);
 	PDI_expose("psize",      psize,  PDI_OUT);
-	PDI_expose("main_field", cur,    PDI_OUT);
 	
 	// the main loop
-	for (; ii<3; ++ii) {
+	for (; ii<10; ++ii) {
 		// share the loop counter & main field at each iteration
+		//*** use PDI_multi_expose to replace PDI_share + event + reclaim
 		PDI_multi_expose("loop",
 				"ii",         &ii, PDI_OUT,
 				"main_field", cur, PDI_OUT,
@@ -202,6 +214,7 @@ int main( int argc, char* argv[] )
 		double (*tmp)[dsize[1]] = cur; cur = next; next = tmp;
 	}
 	// finally share the main field as well as the loop counter after the loop
+	//*** use PDI_multi_expose to replace PDI_share + event + reclaim
 	PDI_multi_expose("finalization",
 	        "main_field", cur, PDI_OUT,
 	        "ii",         &ii, PDI_OUT,