follin/ftrick.d

   1 /* Invisible Vector Library
   2  * coded by Ketmar // Invisible Vector <ketmar@ketmar.no-ip.org>
   3  * Understanding is not required. Only obedience.
   4  *
   5  * This program is free software: you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation, version 3 of the License ONLY.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  16  */
  17 module iv.follin.ftrick /*is aliced*/;
  18
  19 import iv.alice;
  20 import iv.follin.cmacro;
  21
  22 version = follin_use_float_trick;
  23
  24
  25 version(follin_use_float_trick) {
  26   //k8: actually, this is only marginally faster than using `lrintf()`, but...
  27   align(1) union TrickyFloatUnion {
  28   align(1):
  29     float f;
  30     int i;
  31   }
  32   enum declfcvar(string name) = "TrickyFloatUnion "~name~" = void;";
  33   static assert(TrickyFloatUnion.i.sizeof == 4 && TrickyFloatUnion.f.sizeof == 4);
  34   // add (1<<23) to convert to int, then divide by 2^SHIFT, then add 0.5/2^SHIFT to round
  35   //#define check_endianness()
  36   enum MAGIC(string SHIFT) = q{(1.5f*(1<<(23-${SHIFT}))+0.5f/(1<<${SHIFT}))}.cmacroFixVars!("SHIFT")(SHIFT);
  37   enum ADDEND(string SHIFT) = q{(((150-${SHIFT})<<23)+(1<<22))}.cmacroFixVars!("SHIFT")(SHIFT);
  38   enum FAST_SCALED_FLOAT_TO_INT(string x, string s) = q{temp.f = (${x})+${MAGIC}; int v = temp.i-${ADDEND};}
  39     .cmacroFixVars!("x", "s", "MAGIC", "ADDEND")(x, s, MAGIC!(s), ADDEND!(s));
  40 } else {
  41   enum declfcvar(string name) = "{}";
  42   template FAST_SCALED_FLOAT_TO_INT(string x, string s) {
  43     static assert(s == "15");
  44     enum FAST_SCALED_FLOAT_TO_INT = q{import core.stdc.math : lrintf; int v = lrintf((${x})*32768.0f);}.cmacroFixVars!"x"(x);
  45   }
  46 }