arm_max_q7.c

00001 /* ----------------------------------------------------------------------
00002  * Project:      CMSIS DSP Library
00003  * Title:        arm_max_q7.c
00004  * Description:  Maximum value of a Q7 vector
00005  *
00006  * $Date:        27. January 2017
00007  * $Revision:    V.1.5.1
00008  *
00009  * Target Processor: Cortex-M cores
00010  * -------------------------------------------------------------------- */
00011 /*
00012  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
00013  *
00014  * SPDX-License-Identifier: Apache-2.0
00015  *
00016  * Licensed under the Apache License, Version 2.0 (the License); you may
00017  * not use this file except in compliance with the License.
00018  * You may obtain a copy of the License at
00019  *
00020  * www.apache.org/licenses/LICENSE-2.0
00021  *
00022  * Unless required by applicable law or agreed to in writing, software
00023  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
00024  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00025  * See the License for the specific language governing permissions and
00026  * limitations under the License.
00027  */
00028 
00029 #include "arm_math.h"
00030 
00031 /**
00032  * @ingroup groupStats
00033  */
00034 
00035 /**
00036  * @addtogroup Max
00037  * @{
00038  */
00039 
00040 
00041 /**
00042  * @brief Maximum value of a Q7 vector.
00043  * @param[in]       *pSrc points to the input vector
00044  * @param[in]       blockSize length of the input vector
00045  * @param[out]      *pResult maximum value returned here
00046  * @param[out]      *pIndex index of maximum value returned here
00047  * @return none.
00048  */
00049 
00050 void arm_max_q7(
00051   q7_t * pSrc,
00052   uint32_t blockSize,
00053   q7_t * pResult,
00054   uint32_t * pIndex)
00055 {
00056 #if defined (ARM_MATH_DSP)
00057   /* Run the below code for Cortex-M4 and Cortex-M3 */
00058 
00059   q7_t maxVal1, maxVal2, out;                    /* Temporary variables to store the output value. */
00060   uint32_t blkCnt, outIndex, count;              /* loop counter */
00061 
00062   /* Initialise the count value. */
00063   count = 0U;
00064   /* Initialise the index value to zero. */
00065   outIndex = 0U;
00066   /* Load first input value that act as reference value for comparision */
00067   out = *pSrc++;
00068 
00069   /* Loop unrolling */
00070   blkCnt = (blockSize - 1U) >> 2U;
00071 
00072   while (blkCnt > 0U)
00073   {
00074     /* Initialize maxVal to the next consecutive values one by one */
00075     maxVal1 = *pSrc++;
00076     maxVal2 = *pSrc++;
00077 
00078     /* compare for the maximum value */
00079     if (out < maxVal1)
00080     {
00081       /* Update the maximum value and its index */
00082       out = maxVal1;
00083       outIndex = count + 1U;
00084     }
00085 
00086     /* compare for the maximum value */
00087     if (out < maxVal2)
00088     {
00089       /* Update the maximum value and its index */
00090       out = maxVal2;
00091       outIndex = count + 2U;
00092     }
00093 
00094     /* Initialize maxVal to the next consecutive values one by one */
00095     maxVal1 = *pSrc++;
00096     maxVal2 = *pSrc++;
00097 
00098     /* compare for the maximum value */
00099     if (out < maxVal1)
00100     {
00101       /* Update the maximum value and its index */
00102       out = maxVal1;
00103       outIndex = count + 3U;
00104     }
00105 
00106     /* compare for the maximum value */
00107     if (out < maxVal2)
00108     {
00109       /* Update the maximum value and its index */
00110       out = maxVal2;
00111       outIndex = count + 4U;
00112     }
00113 
00114     count += 4U;
00115 
00116     /* Decrement the loop counter */
00117     blkCnt--;
00118   }
00119 
00120   /* if (blockSize - 1U) is not multiple of 4 */
00121   blkCnt = (blockSize - 1U) % 4U;
00122 
00123 #else
00124   /* Run the below code for Cortex-M0 */
00125 
00126   q7_t maxVal1, out;                             /* Temporary variables to store the output value. */
00127   uint32_t blkCnt, outIndex;                     /* loop counter */
00128 
00129   /* Initialise the index value to zero. */
00130   outIndex = 0U;
00131   /* Load first input value that act as reference value for comparision */
00132   out = *pSrc++;
00133 
00134   blkCnt = (blockSize - 1U);
00135 
00136 #endif /* #if defined (ARM_MATH_DSP) */
00137 
00138   while (blkCnt > 0U)
00139   {
00140     /* Initialize maxVal to the next consecutive values one by one */
00141     maxVal1 = *pSrc++;
00142 
00143     /* compare for the maximum value */
00144     if (out < maxVal1)
00145     {
00146       /* Update the maximum value and it's index */
00147       out = maxVal1;
00148       outIndex = blockSize - blkCnt;
00149     }
00150 
00151     /* Decrement the loop counter */
00152     blkCnt--;
00153   }
00154 
00155   /* Store the maximum value and it's index into destination pointers */
00156   *pResult = out;
00157   *pIndex = outIndex;
00158 }
00159 
00160 /**
00161  * @} end of Max group
00162  */
00163