comparison src/fftw-3.3.8/genfft/twiddle.ml @ 167:bd3cc4d1df30

Add FFTW 3.3.8 source, and a Linux build

+(*
+ * Copyright (c) 1997-1999 Massachusetts Institute of Technology
+ * Copyright (c) 2003, 2007-14 Matteo Frigo
+ * Copyright (c) 2003, 2007-14 Massachusetts Institute of Technology
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *)
+
+(* policies for loading/computing twiddle factors *)
+open Complex
+open Util
+
+type twop = TW_FULL | TW_CEXP | TW_NEXT
+
+let optostring = function
+  | TW_CEXP -> "TW_CEXP"
+  | TW_NEXT -> "TW_NEXT"
+  | TW_FULL -> "TW_FULL"
+
+type twinstr = (twop * int * int)
+
+let rec unroll_twfull l = match l with
+| [] -> []
+| (TW_FULL, v, n) :: b ->
+    (forall [] cons 1 n (fun i -> (TW_CEXP, v, i)))
+    @ unroll_twfull b
+| a :: b -> a :: unroll_twfull b
+
+let twinstr_to_c_string l =
+  let one (op, a, b) = Printf.sprintf "{ %s, %d, %d }" (optostring op) a b
+  in let rec loop first = function
+    | [] -> ""
+    | a :: b ->  (if first then "\n" else ",\n") ^ (one a) ^ (loop false b)
+  in "{" ^ (loop true l) ^ "}"
+
+let twinstr_to_simd_string vl l =
+  let one sep = function
+    | (TW_NEXT, 1, 0) -> sep ^ "{TW_NEXT, " ^ vl ^ ", 0}"
+    | (TW_NEXT, _, _) -> failwith "twinstr_to_simd_string"
+    | (TW_CEXP, v, b) -> sep ^ (Printf.sprintf "VTW(%d,%d)" v b)
+    | _ -> failwith "twinstr_to_simd_string"
+  in let rec loop first = function
+    | [] -> ""
+    | a :: b ->  (one (if first then "\n" else ",\n") a) ^ (loop false b)
+  in "{" ^ (loop true (unroll_twfull l)) ^ "}"
+  
+let rec pow m n =
+  if (n = 0) then 1
+  else m * pow m (n - 1)
+
+let rec is_pow m n =
+  n = 1 || ((n mod m) = 0 && is_pow m (n / m))
+
+let rec log m n = if n = 1 then 0 else 1 + log m (n / m)
+
+let rec largest_power_smaller_than m i =
+  if (is_pow m i) then i
+  else largest_power_smaller_than m (i - 1)
+
+let rec smallest_power_larger_than m i =
+  if (is_pow m i) then i
+  else smallest_power_larger_than m (i + 1)
+
+let rec_array n f =
+  let g = ref (fun i -> Complex.zero) in
+  let a = Array.init n (fun i -> lazy (!g i)) in
+  let h i = f (fun i -> Lazy.force a.(i)) i in
+  begin
+    g := h;
+    h
+  end
+
+ 
+let ctimes use_complex_arith a b =
+  if use_complex_arith then
+    Complex.ctimes a b
+  else
+    Complex.times a b
+
+let ctimesj use_complex_arith a b =
+  if use_complex_arith then
+    Complex.ctimesj a b
+  else
+    Complex.times (Complex.conj a) b
+
+let make_bytwiddle sign use_complex_arith g f i =
+  if i = 0 then 
+    f i
+  else if sign = 1 then 
+    ctimes use_complex_arith (g i) (f i)
+  else
+    ctimesj use_complex_arith (g i) (f i)
+
+(* various policies for computing/loading twiddle factors *)
+
+let twiddle_policy_load_all v use_complex_arith =
+  let bytwiddle n sign w f =
+    make_bytwiddle sign use_complex_arith (fun i -> w (i - 1)) f
+  and twidlen n = 2 * (n - 1)
+  and twdesc r = [(TW_FULL, v, r);(TW_NEXT, 1, 0)]
+  in bytwiddle, twidlen, twdesc
+
+(*
+ * if i is a power of two, then load w (log i)
+ * else let x = largest power of 2 less than i in
+ *      let y = i - x in
+ *      compute w^{x+y} = w^x * w^y
+ *)
+let twiddle_policy_log2 v use_complex_arith =
+  let bytwiddle n sign w f =
+    let g = rec_array n (fun self i ->
+      if i = 0 then Complex.one
+      else if is_pow 2 i then w (log 2 i)
+      else let x = largest_power_smaller_than 2 i in
+      let y = i - x in
+	ctimes use_complex_arith (self x) (self y))
+    in make_bytwiddle sign use_complex_arith g f
+  and twidlen n = 2 * (log 2 (largest_power_smaller_than 2 (2 * n - 1)))
+  and twdesc n =
+    (List.flatten 
+       (List.map 
+	  (fun i -> 
+	    if i > 0 && is_pow 2 i then 
+	      [TW_CEXP, v, i] 
+	    else 
+	      [])
+	  (iota n)))
+    @ [(TW_NEXT, 1, 0)]
+  in bytwiddle, twidlen, twdesc
+
+let twiddle_policy_log3 v use_complex_arith =
+  let rec terms_needed i pi s n =
+    if (s >= n - 1) then i
+    else terms_needed (i + 1) (3 * pi) (s + pi) n
+  in
+  let rec bytwiddle n sign w f =
+    let nterms = terms_needed 0 1 0 n in
+    let maxterm = pow 3 (nterms - 1) in
+    let g = rec_array (3 * n) (fun self i ->
+      if i = 0 then Complex.one
+      else if is_pow 3 i then w (log 3 i)
+      else if i = (n - 1) && maxterm >= n then
+	w (nterms - 1)
+      else let x = smallest_power_larger_than 3 i in
+      if (i + i >= x) then
+	let x = min x (n - 1) in
+	  ctimesj use_complex_arith (self (x - i)) (self x)
+      else let x = largest_power_smaller_than 3 i in
+	ctimes use_complex_arith (self (i - x)) (self x))
+    in make_bytwiddle sign use_complex_arith g f
+  and twidlen n = 2 * (terms_needed 0 1 0 n)
+  and twdesc n =
+    (List.map 
+       (fun i -> 
+	  let x = min (pow 3 i) (n - 1) in
+	    TW_CEXP, v, x)
+       (iota ((twidlen n) / 2)))
+    @ [(TW_NEXT, 1, 0)]
+  in bytwiddle, twidlen, twdesc
+    
+let current_twiddle_policy = ref twiddle_policy_load_all
+
+let twiddle_policy use_complex_arith = 
+  !current_twiddle_policy use_complex_arith
+
+let set_policy x = Arg.Unit (fun () -> current_twiddle_policy := x)
+let set_policy_int x = Arg.Int (fun i -> current_twiddle_policy := x i)
+
+let undocumented = " Undocumented twiddle policy"
+
+let speclist = [
+  "-twiddle-load-all", set_policy twiddle_policy_load_all, undocumented;
+  "-twiddle-log2", set_policy twiddle_policy_log2, undocumented;
+  "-twiddle-log3", set_policy twiddle_policy_log3, undocumented;
+]