Implement @silent

Removes item from output of write_array and related methods. Needs careful consideration on how this interacts with unconstrain_array function

Author: WardBrian

src/stan_math_backend/Annotations.ml

@@ -0,0 +1,11 @@
+open Core
+
+let recognized_annotation a =
+  List.mem ["extern"; "silent"] a ~equal:String.equal
+
+let outvar_is_silent Middle.Program.{out_annotations; _} =
+  List.mem out_annotations "silent" ~equal:String.equal
+
+(** Noisy meaning "not silent" *)
+let get_noisy_outvars outvars =
+  List.filter ~f:(fun (_, _, outvar) -> not @@ outvar_is_silent outvar) outvars

src/stan_math_backend/Lower_program.ml

@@ -355,6 +355,7 @@ let gen_get_param_names {Program.output_vars; _} =
       ~f:(fun id -> Exprs.literal_string (Mangle.remove_prefix id))
       (UnsizedType.enumerate_tuple_names_io name (SizedType.to_unsized st))
   in
+  let output_vars = Annotations.get_noisy_outvars output_vars in
   let params, tparams, gqs =
     List.partition3_map output_vars ~f:(function
       | id, _, {Program.out_block= Parameters; out_constrained_st= st; _} ->
@@ -398,6 +399,7 @@ let gen_get_dims {Program.output_vars; _} =
       We should probably deprecate get_dims and replace it with a
       new function later on which returns a more structured type
   *)
+  let output_vars = Annotations.get_noisy_outvars output_vars in
   let cast x = Exprs.static_cast Types.size_t (lower_expr x) in
   let pack inner_dims =
     List.map
@@ -528,6 +530,7 @@ let gen_param_names_fn name (paramvars, tparamvars, gqvars) =
        ~cv_qualifiers:[Const; Final] ())
 
 let gen_constrained_param_names {Program.output_vars; _} =
+  let output_vars = Annotations.get_noisy_outvars output_vars in
   gen_param_names_fn "constrained_param_names"
     (List.partition3_map
        ~f:(function
@@ -598,7 +601,8 @@ let gen_overloads {Program.output_vars; _} =
         Expr.Helpers.binop_list
           (List.map
              ~f:(fun outvar ->
-               SizedType.io_size outvar.Program.out_constrained_st)
+               if Annotations.outvar_is_silent outvar then Expr.Helpers.zero
+               else SizedType.io_size outvar.Program.out_constrained_st)
              outvars)
           Operator.Plus ~default:Expr.Helpers.zero
         |> lower_expr in

src/stan_math_backend/Transform_Mir.ml

@@ -1012,8 +1012,6 @@ let map_prog_stmt_lists f (p : ('a, 'b, 'c) Program.t) =
   ; transform_inits= f p.transform_inits
   ; unconstrain_array= f p.unconstrain_array }
 
-let recognized_annotation a = a = "extern"
-
 let trans_prog (p : Program.Typed.t) =
   (* name mangling of c++ keywords*)
   let rec map_stmt {Stmt.Fixed.pattern; meta} =
@@ -1061,8 +1059,9 @@ let trans_prog (p : Program.Typed.t) =
     then init_pos @ stmts
     else stmts in
   let param_writes, tparam_writes, gq_writes =
-    List.map p.output_vars ~f:param_unconstrained_serializer_write
-    |> List.map2_exn p.output_vars ~f:(fun (_, meta, outvar) writes ->
+    let loud_output_vars = Annotations.get_noisy_outvars p.output_vars in
+    List.map loud_output_vars ~f:param_unconstrained_serializer_write
+    |> List.map2_exn loud_output_vars ~f:(fun (_, meta, outvar) writes ->
            (outvar.Program.out_block, Stmt.Fixed.{pattern= SList writes; meta}))
     |> List.partition3_map ~f:(fun (b, x) ->
            match b with

src/stan_math_backend/Transform_Mir.mli

@@ -7,4 +7,3 @@ open Middle
 val trans_prog : Program.Typed.t -> Program.Typed.t
 val is_opencl_var : string -> bool
 val use_opencl : bool ref
-val recognized_annotation : string -> bool

src/stanc/stanc.ml

@@ -286,7 +286,8 @@ let use_file filename =
       ~print_warnings:(not !canonicalize_settings.deprecations)
       ~bare_functions:!bare_functions in
   let unused_annotations =
-    Annotations.find_unrecognized Transform_Mir.recognized_annotation ast in
+    Frontend.Annotations.find_unrecognized
+      Stan_math_backend.Annotations.recognized_annotation ast in
   Warnings.pp_warnings ?printed_filename Fmt.stderr unused_annotations;
   Debugging.ast_logger ast;
   let typed_ast = type_ast_or_exit ?printed_filename ast in