Line data    Source code

       1             : //# ExpCache.cc: Implementation of ExpCache (tabulated exponential) class
       2             : //# Copyright (C) 1997,1998,1999,2000,2001,2002,2003
       3             : //# Associated Universities, Inc. Washington DC, USA.
       4             : //#
       5             : //# This library is free software; you can redistribute it and/or modify it
       6             : //# under the terms of the GNU Library General Public License as published by
       7             : //# the Free Software Foundation; either version 2 of the License, or (at your
       8             : //# option) any later version.
       9             : //#
      10             : //# This library is distributed in the hope that it will be useful, but WITHOUT
      11             : //# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
      12             : //# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
      13             : //# License for more details.
      14             : //#
      15             : //# You should have received a copy of the GNU Library General Public License
      16             : //# along with this library; if not, write to the Free Software Foundation,
      17             : //# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
      18             : //#
      19             : //# Correspondence concerning AIPS++ should be addressed as follows:
      20             : //#        Internet email: casa-feedback@nrao.edu.
      21             : //#        Postal address: AIPS++ Project Office
      22             : //#                        National Radio Astronomy Observatory
      23             : //#                        520 Edgemont Road
      24             : //#                        Charlottesville, VA 22903-2475 USA
      25             : //#
      26             : //# $Id$
      27             : 
      28             : #if !defined(EXP_CACHE_H)
      29             : #define EXP_CACHE_H
      30             : 
      31             : #include <stdlib.h>
      32             : #include <math.h>
      33             : 
      34             : namespace casa
      35             : {
      36             : template<class T> class ExpCache
      37             : {
      38             : public:
      39          20 :   ExpCache() {EStep=0; ETable=NULL;Size=0;};
      40             :   ExpCache(int n, T Step) {EStep=Size=0;ETable=NULL;Build(n,Step);};
      41          20 :   ~ExpCache() {if (ETable) free(ETable);};
      42             : 
      43             :   inline void build(int n, T Step)
      44             :   {
      45             :     if (ETable) free(ETable);
      46             : 
      47             :     ETable=(T *)malloc(sizeof(T)*n);
      48             :     Size = n;
      49             :     EStep = Step;
      50             : 
      51             :     for (int i=0;i<n;i++) ETable[i]=exp(-i*Step);
      52             :   }
      53           0 :   inline T operator()(T arg) 
      54             :   {
      55           0 :     int N=(int)(-arg/EStep); 
      56             : 
      57             :     //    return (fabs(N)>=Size)?0:((ETable[N]-ETable[N+1])*arg + ETable[N]);
      58             : 
      59           0 :     return (abs(N)>=Size)?0:ETable[N];
      60             :   }
      61             : private:
      62             :   T EStep;
      63             :   T *ETable;
      64             :   int Size;
      65             : };
      66             : }; 
      67             : #endif