Fix number of rounds in Segmented Ring

patrick96 · patrick96 · commit e898b28357e5 · 2022-01-13T00:27:56.000+01:00
diff --git a/notes/cost-model/allreduce-ring-segmented.c b/notes/cost-model/allreduce-ring-segmented.c
@@ -100,7 +100,7 @@ const int phase_count = block_count / num_phases;
  *
  *     phase_count ADDs
  *
- * P rounds
+ * P - 1 rounds
  *
  *     o + L + (block_count * 8 - 1) * G + g
  */
@@ -305,7 +305,7 @@ int allreduce_ring_segmented(const void *sbuf, void *rbuf, int count) {
     /* Distribution loop - variation of ring allgather */
     send_to = (rank + 1) % size;
     recv_from = (rank + size - 1) % size;
-    // #### P rounds
+    // #### P -1 rounds
     for (k = 0; k < size - 1; k++) {
         const int recv_data_from = (rank + size - k) % size;
         const int send_data_from = (rank + 1 + size - k) % size;

Original file line number	Diff line number	Diff line change
`@@ -100,7 +100,7 @@ const int phase_count = block_count / num_phases;`
`100`	`100`	`*`
`101`	`101`	`* phase_count ADDs`
`102`	`102`	`*`
`103`		`- * P rounds`
	`103`	`+ * P - 1 rounds`
`104`	`104`	`*`
`105`	`105`	`* o + L + (block_count * 8 - 1) * G + g`
`106`	`106`	`*/`
`@@ -305,7 +305,7 @@ int allreduce_ring_segmented(const void sbuf, void rbuf, int count) {`
`305`	`305`	`/* Distribution loop - variation of ring allgather */`
`306`	`306`	`send_to = (rank + 1) % size;`
`307`	`307`	`recv_from = (rank + size - 1) % size;`
`308`		`- // #### P rounds`
	`308`	`+ // #### P -1 rounds`
`309`	`309`	`for (k = 0; k < size - 1; k++) {`
`310`	`310`	`const int recv_data_from = (rank + size - k) % size;`
`311`	`311`	`const int send_data_from = (rank + 1 + size - k) % size;`