add reverse modulo mapping context

codes/codes-mapping-context.h

@@ -29,6 +29,8 @@ enum codes_mctx_type {
     // the number of callees in the group, to provide simple wraparound
     // behaviour
     CODES_MCTX_GROUP_MODULO,
+    // similar to GROUP_MODULO, but maps to offsets in reverse order
+    CODES_MCTX_GROUP_MODULO_REVERSE,
     // instructs those using the context to map into the same group/repetition
     // and directly to a callee offset
     CODES_MCTX_GROUP_DIRECT,
@@ -52,6 +54,7 @@ struct codes_mctx_global_direct {
 struct codes_mctx_group_modulo {
     struct codes_mctx_annotation anno;
 };
+// NOTE: group_modulo_reverse shares the group_modulo representation
 
 struct codes_mctx_group_direct {
     struct codes_mctx_annotation anno;
@@ -74,6 +77,10 @@ struct codes_mctx codes_mctx_set_group_modulo(
         char const * annotation,
         bool ignore_annotations);
 
+struct codes_mctx codes_mctx_set_group_modulo_reverse(
+        char const * annotation,
+        bool ignore_annotations);
+
 struct codes_mctx codes_mctx_set_group_direct(
         int offset,
         char const * annotation,

src/util/codes-mapping-context.c

@@ -27,12 +27,14 @@ struct codes_mctx codes_mctx_set_global_direct(tw_lpid lpid)
     rtn.u.global_direct.lpid = lpid;
     return rtn;
 }
-struct codes_mctx codes_mctx_set_group_modulo(
+
+static struct codes_mctx set_group_modulo_common(
+        enum codes_mctx_type type,
         char const * annotation,
         bool ignore_annotations)
 {
     struct codes_mctx rtn;
-    rtn.type = CODES_MCTX_GROUP_MODULO;
+    rtn.type = type;
     if (ignore_annotations)
         rtn.u.group_modulo.anno.cid = -1;
     else
@@ -40,6 +42,22 @@ struct codes_mctx codes_mctx_set_group_modulo(
             codes_mapping_get_anno_cid_by_name(annotation);
     return rtn;
 }
+struct codes_mctx codes_mctx_set_group_modulo(
+        char const * annotation,
+        bool ignore_annotations)
+{
+    return set_group_modulo_common(CODES_MCTX_GROUP_MODULO, annotation,
+            ignore_annotations);
+}
+
+struct codes_mctx codes_mctx_set_group_modulo_reverse(
+        char const * annotation,
+        bool ignore_annotations)
+{
+    return set_group_modulo_common(CODES_MCTX_GROUP_MODULO_REVERSE, annotation,
+            ignore_annotations);
+}
+
 struct codes_mctx codes_mctx_set_group_direct(
         int offset,
         char const * annotation,
@@ -69,6 +87,7 @@ tw_lpid codes_mctx_to_lpid(
         case CODES_MCTX_GLOBAL_DIRECT:
             return ctx->u.global_direct.lpid;
         case CODES_MCTX_GROUP_MODULO:
+        case CODES_MCTX_GROUP_MODULO_REVERSE:
             anno = &ctx->u.group_modulo.anno;
             break;
         case CODES_MCTX_GROUP_DIRECT:
@@ -92,7 +111,8 @@ tw_lpid codes_mctx_to_lpid(
         anno_str = codes_mapping_get_anno_name_by_cid(anno->cid);
 
     int dest_offset;
-    if (ctx->type == CODES_MCTX_GROUP_MODULO) {
+    if (ctx->type == CODES_MCTX_GROUP_MODULO ||
+            ctx->type == CODES_MCTX_GROUP_MODULO_REVERSE) {
         int num_dest_lps = codes_mapping_get_lp_count(sender_group, 1,
                 dest_lp_name, anno_str, anno->cid == -1);
         if (num_dest_lps == 0)
@@ -104,6 +124,8 @@ tw_lpid codes_mctx_to_lpid(
                     codes_mapping_get_anno_name_by_cid(anno->cid));
 
         dest_offset = offset % num_dest_lps;
+        if (ctx->type == CODES_MCTX_GROUP_MODULO_REVERSE)
+            dest_offset = num_dest_lps - 1 - dest_offset;
     }
     else if (ctx->type == CODES_MCTX_GROUP_DIRECT) {
         dest_offset = ctx->u.group_direct.offset;
@@ -126,6 +148,7 @@ char const * codes_mctx_get_annotation(
         case CODES_MCTX_GLOBAL_DIRECT:
             return codes_mapping_get_annotation_by_lpid(sender_id);
         case CODES_MCTX_GROUP_MODULO:
+        case CODES_MCTX_GROUP_MODULO_REVERSE:
             // if not ignoring the annotation, just return what's in the
             // context
             if (ctx->u.group_modulo.anno.cid >= 0)

tests/map-ctx-test.c

@@ -24,14 +24,16 @@ int main(int argc, char *argv[])
     if (rc != 0)
         ERR("unable to load configuration file %s", argv[1]);
 
-    struct codes_mctx direct, group_modulo, group_direct,
-                      group_modulo_anno, group_direct_anno;
+    struct codes_mctx direct, group_modulo, group_rmodulo, group_direct,
+                      group_modulo_anno, group_rmodulo_anno, group_direct_anno;
 
-    direct            = codes_mctx_set_global_direct(12ul);
-    group_modulo      = codes_mctx_set_group_modulo(NULL, true);
-    group_direct      = codes_mctx_set_group_direct(1, NULL, true);
-    group_modulo_anno = codes_mctx_set_group_modulo("baz", false);
-    group_direct_anno = codes_mctx_set_group_direct(1, "baz", false);
+    direct              = codes_mctx_set_global_direct(12ul);
+    group_modulo        = codes_mctx_set_group_modulo(NULL, true);
+    group_rmodulo       = codes_mctx_set_group_modulo_reverse(NULL, true);
+    group_direct        = codes_mctx_set_group_direct(1, NULL, true);
+    group_modulo_anno   = codes_mctx_set_group_modulo("baz", false);
+    group_rmodulo_anno  = codes_mctx_set_group_modulo_reverse("baz", false);
+    group_direct_anno   = codes_mctx_set_group_direct(1, "baz", false);
 
     tw_lpid in;
     tw_lpid rtn_id;
@@ -54,6 +56,14 @@ int main(int argc, char *argv[])
     if (rtn_anno)
         ERR("group_modulo mapping: expected NULL anno, got %s", rtn_anno);
 
+    rtn_id = codes_mctx_to_lpid(&group_rmodulo, "bar", in);
+    if (rtn_id != 9ul)
+        ERR("group_rmodulo mapping: expected %lu, got %lu",
+                9ul, rtn_id);
+    rtn_anno = codes_mctx_get_annotation(&group_rmodulo, "bar", in);
+    if (rtn_anno)
+        ERR("group_rmodulo mapping: expected NULL anno, got %s", rtn_anno);
+
     in = 12ul;
     rtn_id = codes_mctx_to_lpid(&group_modulo, "bar", in);
     if (rtn_id != 13ul)
@@ -63,6 +73,14 @@ int main(int argc, char *argv[])
     if (rtn_anno)
         ERR("group_modulo mapping: expected NULL anno, got %s", rtn_anno);
 
+    rtn_id = codes_mctx_to_lpid(&group_rmodulo, "bar", in);
+    if (rtn_id != 14ul)
+        ERR("group_rmodulo mapping: expected %lu, got %lu",
+                14ul, rtn_id);
+    rtn_anno = codes_mctx_get_annotation(&group_rmodulo, "bar", in);
+    if (rtn_anno)
+        ERR("group_rmodulo mapping: expected NULL anno, got %s", rtn_anno);
+
     rtn_id = codes_mctx_to_lpid(CODES_MCTX_DEFAULT, "bar", in);
     if (rtn_id != 13ul)
         ERR("group_modulo mapping (default): expected %lu, got %lu",
@@ -79,6 +97,14 @@ int main(int argc, char *argv[])
     if (strcmp(rtn_anno,"baz") != 0)
         ERR("group_modulo mapping: expected anno \"baz\", got %s", rtn_anno);
 
+    rtn_id = codes_mctx_to_lpid(&group_rmodulo_anno, "bar", in);
+    if (rtn_id != 16ul)
+        ERR("group_rmodulo annotated mapping: expected %lu, got %lu",
+                16ul, rtn_id);
+    rtn_anno = codes_mctx_get_annotation(&group_rmodulo_anno, "bar", in);
+    if (strcmp(rtn_anno,"baz") != 0)
+        ERR("group_rmodulo mapping: expected anno \"baz\", got %s", rtn_anno);
+
     in = 10ul;
     rtn_id = codes_mctx_to_lpid(&group_direct, "bar", in);
     if (rtn_id != 14ul)