1 /*
2  * Copyright (C) 2004-2010 NXP Software
3  * Copyright (C) 2010 The Android Open Source Project
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  *      http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17 
18 #include "LVM_Types.h"
19 #include "LVM_Macros.h"
20 #include "ScalarArithmetic.h"
21 
22 /*-------------------------------------------------------------------------*/
23 /* FUNCTION:                                                               */
24 /*   LVM_Polynomial                                                        */
25 /*                                                                         */
26 /* DESCRIPTION:                                                            */
27 /*   This function performs polynomial expansion                           */
28 /*  Y = (A0 + A1*X + A2*X2 + A3*X3 + �.. + AN*xN) << AN+1                  */
29 /*                                                                         */
30 /*  LVM_INT32 LVM_Polynomial(LVM_UINT16    N,                              */
31 /*                           LVM_INT32    *pCoefficients,                  */
32 /*                           LVM_INT32    X)                               */
33 /*                                                                         */
34 /* PARAMETERS:                                                             */
35 /*                                                                         */
36 /*  N                is the polynomial order                               */
37 /*  pCoefficients    is the ptr to polynomial coefficients A0,A1.. in Q.31 */
38 /*  X                is the input variable                                 */
39 /*                                                                         */
40 /* RETURNS:                                                                */
41 /*   The result of the polynomial expansion in Q1.31 format                */
42 /*-------------------------------------------------------------------------*/
43 LVM_FLOAT LVM_Polynomial(LVM_UINT16    N,
44                          LVM_FLOAT    *pCoefficients,
45                          LVM_FLOAT    X)
46 {
47     LVM_INT32 i;
48     LVM_FLOAT Y,A,XTemp,Temp,sign;
49 
50     Y = *pCoefficients; /* Y=A0*/
51     pCoefficients++;
52 
53     if(X == -1.0f)
54     {
55         Temp = -1;
56         sign = Temp;
57         for(i = 1; i <= N; i++)
58         {
59             Y += ((*pCoefficients) * sign);
60             pCoefficients++;
61             sign *= Temp;
62         }
63 
64     }
65     else
66     {
67         XTemp = X;
68         for(i = N-1; i >= 0; i--)
69         {
70             A = *pCoefficients;
71             pCoefficients++;
72 
73             Temp = A * XTemp;
74             Y += Temp;
75 
76             Temp = XTemp * X;
77             XTemp = Temp;
78         }
79     }
80     return Y;
81 }
82