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# arm_correlate_fast_q31.c

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    00001 /* ----------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        15. July 2011
    00005 * $Revision:    V1.0.10
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_correlate_fast_q31.c
    00009 *
    00010 * Description:  Fast Q31 Correlation.
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3
    00013 *
    00014 * Version 1.0.10 2011/7/15
    00015 *    Big Endian support added and Merged M0 and M3/M4 Source code.
    00016 *
    00017 * Version 1.0.3 2010/11/29
    00018 *    Re-organized the CMSIS folders and updated documentation.
    00019 *
    00020 * Version 1.0.2 2010/11/11
    00021 *    Documentation updated.
    00022 *
    00023 * Version 1.0.1 2010/10/05
    00024 *    Production release and review comments incorporated.
    00025 *
    00026 * Version 1.0.0 2010/09/20
    00027 *    Production release and review comments incorporated.
    00028 * -------------------------------------------------------------------- */
    00029
    00030 #include "arm_math.h"
    00031
    00070 void arm_correlate_fast_q31(
    00071   q31_t * pSrcA,
    00072   uint32_t srcALen,
    00073   q31_t * pSrcB,
    00074   uint32_t srcBLen,
    00075   q31_t * pDst)
    00076 {
    00077   q31_t *pIn1;                                   /* inputA pointer               */
    00078   q31_t *pIn2;                                   /* inputB pointer               */
    00079   q31_t *pOut = pDst;                            /* output pointer               */
    00080   q31_t *px;                                     /* Intermediate inputA pointer  */
    00081   q31_t *py;                                     /* Intermediate inputB pointer  */
    00082   q31_t *pSrc1;                                  /* Intermediate pointers        */
    00083   q31_t sum, acc0, acc1, acc2, acc3;             /* Accumulators                  */
    00084   q31_t x0, x1, x2, x3, c0;                      /* temporary variables for holding input and coefficient values */
    00085   uint32_t j, k = 0u, count, blkCnt, outBlockSize, blockSize1, blockSize2, blockSize3;  /* loop counter                 */
    00086   int32_t inc = 1;                               /* Destination address modifier */
    00087
    00088
    00089   /* The algorithm implementation is based on the lengths of the inputs. */
    00090   /* srcB is always made to slide across srcA. */
    00091   /* So srcBLen is always considered as shorter or equal to srcALen */
    00092   if(srcALen >= srcBLen)
    00093   {
    00094     /* Initialization of inputA pointer */
    00095     pIn1 = (pSrcA);
    00096
    00097     /* Initialization of inputB pointer */
    00098     pIn2 = (pSrcB);
    00099
    00100     /* Number of output samples is calculated */
    00101     outBlockSize = (2u * srcALen) - 1u;
    00102
    00103     /* When srcALen > srcBLen, zero padding is done to srcB
    00104      * to make their lengths equal.
    00105      * Instead, (outBlockSize - (srcALen + srcBLen - 1))
    00106      * number of output samples are made zero */
    00107     j = outBlockSize - (srcALen + (srcBLen - 1u));
    00108
    00109     /* Updating the pointer position to non zero value */
    00110     pOut += j;
    00111
    00112   }
    00113   else
    00114   {
    00115     /* Initialization of inputA pointer */
    00116     pIn1 = (pSrcB);
    00117
    00118     /* Initialization of inputB pointer */
    00119     pIn2 = (pSrcA);
    00120
    00121     /* srcBLen is always considered as shorter or equal to srcALen */
    00122     j = srcBLen;
    00123     srcBLen = srcALen;
    00124     srcALen = j;
    00125
    00126     /* CORR(x, y) = Reverse order(CORR(y, x)) */
    00127     /* Hence set the destination pointer to point to the last output sample */
    00128     pOut = pDst + ((srcALen + srcBLen) - 2u);
    00129
    00130     /* Destination address modifier is set to -1 */
    00131     inc = -1;
    00132
    00133   }
    00134
    00135   /* The function is internally
    00136    * divided into three parts according to the number of multiplications that has to be
    00137    * taken place between inputA samples and inputB samples. In the first part of the
    00138    * algorithm, the multiplications increase by one for every iteration.
    00139    * In the second part of the algorithm, srcBLen number of multiplications are done.
    00140    * In the third part of the algorithm, the multiplications decrease by one
    00141    * for every iteration.*/
    00142   /* The algorithm is implemented in three stages.
    00143    * The loop counters of each stage is initiated here. */
    00144   blockSize1 = srcBLen - 1u;
    00145   blockSize2 = srcALen - (srcBLen - 1u);
    00146   blockSize3 = blockSize1;
    00147
    00148   /* --------------------------
    00149    * Initializations of stage1
    00150    * -------------------------*/
    00151
    00152   /* sum = x[0] * y[srcBlen - 1]
    00153    * sum = x[0] * y[srcBlen - 2] + x[1] * y[srcBlen - 1]
    00154    * ....
    00155    * sum = x[0] * y[0] + x[1] * y[1] +...+ x[srcBLen - 1] * y[srcBLen - 1]
    00156    */
    00157
    00158   /* In this stage the MAC operations are increased by 1 for every iteration.
    00159      The count variable holds the number of MAC operations performed */
    00160   count = 1u;
    00161
    00162   /* Working pointer of inputA */
    00163   px = pIn1;
    00164
    00165   /* Working pointer of inputB */
    00166   pSrc1 = pIn2 + (srcBLen - 1u);
    00167   py = pSrc1;
    00168
    00169   /* ------------------------
    00170    * Stage1 process
    00171    * ----------------------*/
    00172
    00173   /* The first stage starts here */
    00174   while(blockSize1 > 0u)
    00175   {
    00176     /* Accumulator is made zero for every iteration */
    00177     sum = 0;
    00178
    00179     /* Apply loop unrolling and compute 4 MACs simultaneously. */
    00180     k = count >> 2;
    00181
    00182     /* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
    00183      ** a second loop below computes MACs for the remaining 1 to 3 samples. */
    00184     while(k > 0u)
    00185     {
    00186       /* x[0] * y[srcBLen - 4] */
    00187       sum = (q31_t) ((((q63_t) sum << 32) +
    00188                       ((q63_t) * px++ * (*py++))) >> 32);
    00189       /* x[1] * y[srcBLen - 3] */
    00190       sum = (q31_t) ((((q63_t) sum << 32) +
    00191                       ((q63_t) * px++ * (*py++))) >> 32);
    00192       /* x[2] * y[srcBLen - 2] */
    00193       sum = (q31_t) ((((q63_t) sum << 32) +
    00194                       ((q63_t) * px++ * (*py++))) >> 32);
    00195       /* x[3] * y[srcBLen - 1] */
    00196       sum = (q31_t) ((((q63_t) sum << 32) +
    00197                       ((q63_t) * px++ * (*py++))) >> 32);
    00198
    00199       /* Decrement the loop counter */
    00200       k--;
    00201     }
    00202
    00203     /* If the count is not a multiple of 4, compute any remaining MACs here.
    00204      ** No loop unrolling is used. */
    00205     k = count % 0x4u;
    00206
    00207     while(k > 0u)
    00208     {
    00209       /* Perform the multiply-accumulates */
    00210       /* x[0] * y[srcBLen - 1] */
    00211       sum = (q31_t) ((((q63_t) sum << 32) +
    00212                       ((q63_t) * px++ * (*py++))) >> 32);
    00213
    00214       /* Decrement the loop counter */
    00215       k--;
    00216     }
    00217
    00218     /* Store the result in the accumulator in the destination buffer. */
    00219     *pOut = sum << 1;
    00220     /* Destination pointer is updated according to the address modifier, inc */
    00221     pOut += inc;
    00222
    00223     /* Update the inputA and inputB pointers for next MAC calculation */
    00224     py = pSrc1 - count;
    00225     px = pIn1;
    00226
    00227     /* Increment the MAC count */
    00228     count++;
    00229
    00230     /* Decrement the loop counter */
    00231     blockSize1--;
    00232   }
    00233
    00234   /* --------------------------
    00235    * Initializations of stage2
    00236    * ------------------------*/
    00237
    00238   /* sum = x[0] * y[0] + x[1] * y[1] +...+ x[srcBLen-1] * y[srcBLen-1]
    00239    * sum = x[1] * y[0] + x[2] * y[1] +...+ x[srcBLen] * y[srcBLen-1]
    00240    * ....
    00241    * sum = x[srcALen-srcBLen-2] * y[0] + x[srcALen-srcBLen-1] * y[1] +...+ x[srcALen-1] * y[srcBLen-1]
    00242    */
    00243
    00244   /* Working pointer of inputA */
    00245   px = pIn1;
    00246
    00247   /* Working pointer of inputB */
    00248   py = pIn2;
    00249
    00250   /* count is index by which the pointer pIn1 to be incremented */
    00251   count = 1u;
    00252
    00253   /* -------------------
    00254    * Stage2 process
    00255    * ------------------*/
    00256
    00257   /* Stage2 depends on srcBLen as in this stage srcBLen number of MACS are performed.
    00258    * So, to loop unroll over blockSize2,
    00259    * srcBLen should be greater than or equal to 4 */
    00260   if(srcBLen >= 4u)
    00261   {
    00262     /* Loop unroll over blockSize2, by 4 */
    00263     blkCnt = blockSize2 >> 2u;
    00264
    00265     while(blkCnt > 0u)
    00266     {
    00267       /* Set all accumulators to zero */
    00268       acc0 = 0;
    00269       acc1 = 0;
    00270       acc2 = 0;
    00271       acc3 = 0;
    00272
    00273       /* read x[0], x[1], x[2] samples */
    00274       x0 = *(px++);
    00275       x1 = *(px++);
    00276       x2 = *(px++);
    00277
    00278       /* Apply loop unrolling and compute 4 MACs simultaneously. */
    00279       k = srcBLen >> 2u;
    00280
    00281       /* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
    00282        ** a second loop below computes MACs for the remaining 1 to 3 samples. */
    00283       do
    00284       {
    00285         /* Read y[0] sample */
    00286         c0 = *(py++);
    00287
    00288         /* Read x[3] sample */
    00289         x3 = *(px++);
    00290
    00291         /* Perform the multiply-accumulate */
    00292         /* acc0 +=  x[0] * y[0] */
    00293         acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
    00294         /* acc1 +=  x[1] * y[0] */
    00295         acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
    00296         /* acc2 +=  x[2] * y[0] */
    00297         acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x2 * c0)) >> 32);
    00298         /* acc3 +=  x[3] * y[0] */
    00299         acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x3 * c0)) >> 32);
    00300
    00301         /* Read y[1] sample */
    00302         c0 = *(py++);
    00303
    00304         /* Read x[4] sample */
    00305         x0 = *(px++);
    00306
    00307         /* Perform the multiply-accumulates */
    00308         /* acc0 +=  x[1] * y[1] */
    00309         acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x1 * c0)) >> 32);
    00310         /* acc1 +=  x[2] * y[1] */
    00311         acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x2 * c0)) >> 32);
    00312         /* acc2 +=  x[3] * y[1] */
    00313         acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x3 * c0)) >> 32);
    00314         /* acc3 +=  x[4] * y[1] */
    00315         acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x0 * c0)) >> 32);
    00316
    00317         /* Read y[2] sample */
    00318         c0 = *(py++);
    00319
    00320         /* Read x[5] sample */
    00321         x1 = *(px++);
    00322
    00323         /* Perform the multiply-accumulates */
    00324         /* acc0 +=  x[2] * y[2] */
    00325         acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x2 * c0)) >> 32);
    00326         /* acc1 +=  x[3] * y[2] */
    00327         acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x3 * c0)) >> 32);
    00328         /* acc2 +=  x[4] * y[2] */
    00329         acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x0 * c0)) >> 32);
    00330         /* acc3 +=  x[5] * y[2] */
    00331         acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x1 * c0)) >> 32);
    00332
    00333         /* Read y[3] sample */
    00334         c0 = *(py++);
    00335
    00336         /* Read x[6] sample */
    00337         x2 = *(px++);
    00338
    00339         /* Perform the multiply-accumulates */
    00340         /* acc0 +=  x[3] * y[3] */
    00341         acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x3 * c0)) >> 32);
    00342         /* acc1 +=  x[4] * y[3] */
    00343         acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x0 * c0)) >> 32);
    00344         /* acc2 +=  x[5] * y[3] */
    00345         acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x1 * c0)) >> 32);
    00346         /* acc3 +=  x[6] * y[3] */
    00347         acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x2 * c0)) >> 32);
    00348
    00349
    00350       } while(--k);
    00351
    00352       /* If the srcBLen is not a multiple of 4, compute any remaining MACs here.
    00353        ** No loop unrolling is used. */
    00354       k = srcBLen % 0x4u;
    00355
    00356       while(k > 0u)
    00357       {
    00358         /* Read y[4] sample */
    00359         c0 = *(py++);
    00360
    00361         /* Read x[7] sample */
    00362         x3 = *(px++);
    00363
    00364         /* Perform the multiply-accumulates */
    00365         /* acc0 +=  x[4] * y[4] */
    00366         acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
    00367         /* acc1 +=  x[5] * y[4] */
    00368         acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
    00369         /* acc2 +=  x[6] * y[4] */
    00370         acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x2 * c0)) >> 32);
    00371         /* acc3 +=  x[7] * y[4] */
    00372         acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x3 * c0)) >> 32);
    00373
    00374         /* Reuse the present samples for the next MAC */
    00375         x0 = x1;
    00376         x1 = x2;
    00377         x2 = x3;
    00378
    00379         /* Decrement the loop counter */
    00380         k--;
    00381       }
    00382
    00383       /* Store the result in the accumulator in the destination buffer. */
    00384       *pOut = (q31_t) (acc0 << 1);
    00385       /* Destination pointer is updated according to the address modifier, inc */
    00386       pOut += inc;
    00387
    00388       *pOut = (q31_t) (acc1 << 1);
    00389       pOut += inc;
    00390
    00391       *pOut = (q31_t) (acc2 << 1);
    00392       pOut += inc;
    00393
    00394       *pOut = (q31_t) (acc3 << 1);
    00395       pOut += inc;
    00396
    00397       /* Update the inputA and inputB pointers for next MAC calculation */
    00398       px = pIn1 + (count * 4u);
    00399       py = pIn2;
    00400
    00401       /* Increment the pointer pIn1 index, count by 1 */
    00402       count++;
    00403
    00404       /* Decrement the loop counter */
    00405       blkCnt--;
    00406     }
    00407
    00408     /* If the blockSize2 is not a multiple of 4, compute any remaining output samples here.
    00409      ** No loop unrolling is used. */
    00410     blkCnt = blockSize2 % 0x4u;
    00411
    00412     while(blkCnt > 0u)
    00413     {
    00414       /* Accumulator is made zero for every iteration */
    00415       sum = 0;
    00416
    00417       /* Apply loop unrolling and compute 4 MACs simultaneously. */
    00418       k = srcBLen >> 2u;
    00419
    00420       /* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
    00421        ** a second loop below computes MACs for the remaining 1 to 3 samples. */
    00422       while(k > 0u)
    00423       {
    00424         /* Perform the multiply-accumulates */
    00425         sum = (q31_t) ((((q63_t) sum << 32) +
    00426                         ((q63_t) * px++ * (*py++))) >> 32);
    00427         sum = (q31_t) ((((q63_t) sum << 32) +
    00428                         ((q63_t) * px++ * (*py++))) >> 32);
    00429         sum = (q31_t) ((((q63_t) sum << 32) +
    00430                         ((q63_t) * px++ * (*py++))) >> 32);
    00431         sum = (q31_t) ((((q63_t) sum << 32) +
    00432                         ((q63_t) * px++ * (*py++))) >> 32);
    00433
    00434         /* Decrement the loop counter */
    00435         k--;
    00436       }
    00437
    00438       /* If the srcBLen is not a multiple of 4, compute any remaining MACs here.
    00439        ** No loop unrolling is used. */
    00440       k = srcBLen % 0x4u;
    00441
    00442       while(k > 0u)
    00443       {
    00444         /* Perform the multiply-accumulate */
    00445         sum = (q31_t) ((((q63_t) sum << 32) +
    00446                         ((q63_t) * px++ * (*py++))) >> 32);
    00447
    00448         /* Decrement the loop counter */
    00449         k--;
    00450       }
    00451
    00452       /* Store the result in the accumulator in the destination buffer. */
    00453       *pOut = sum << 1;
    00454       /* Destination pointer is updated according to the address modifier, inc */
    00455       pOut += inc;
    00456
    00457       /* Update the inputA and inputB pointers for next MAC calculation */
    00458       px = pIn1 + count;
    00459       py = pIn2;
    00460
    00461       /* Increment the MAC count */
    00462       count++;
    00463
    00464       /* Decrement the loop counter */
    00465       blkCnt--;
    00466     }
    00467   }
    00468   else
    00469   {
    00470     /* If the srcBLen is not a multiple of 4,
    00471      * the blockSize2 loop cannot be unrolled by 4 */
    00472     blkCnt = blockSize2;
    00473
    00474     while(blkCnt > 0u)
    00475     {
    00476       /* Accumulator is made zero for every iteration */
    00477       sum = 0;
    00478
    00479       /* Loop over srcBLen */
    00480       k = srcBLen;
    00481
    00482       while(k > 0u)
    00483       {
    00484         /* Perform the multiply-accumulate */
    00485         sum = (q31_t) ((((q63_t) sum << 32) +
    00486                         ((q63_t) * px++ * (*py++))) >> 32);
    00487
    00488         /* Decrement the loop counter */
    00489         k--;
    00490       }
    00491
    00492       /* Store the result in the accumulator in the destination buffer. */
    00493       *pOut = sum << 1;
    00494       /* Destination pointer is updated according to the address modifier, inc */
    00495       pOut += inc;
    00496
    00497       /* Update the inputA and inputB pointers for next MAC calculation */
    00498       px = pIn1 + count;
    00499       py = pIn2;
    00500
    00501       /* Increment the MAC count */
    00502       count++;
    00503
    00504       /* Decrement the loop counter */
    00505       blkCnt--;
    00506     }
    00507   }
    00508
    00509   /* --------------------------
    00510    * Initializations of stage3
    00511    * -------------------------*/
    00512
    00513   /* sum += x[srcALen-srcBLen+1] * y[0] + x[srcALen-srcBLen+2] * y[1] +...+ x[srcALen-1] * y[srcBLen-1]
    00514    * sum += x[srcALen-srcBLen+2] * y[0] + x[srcALen-srcBLen+3] * y[1] +...+ x[srcALen-1] * y[srcBLen-1]
    00515    * ....
    00516    * sum +=  x[srcALen-2] * y[0] + x[srcALen-1] * y[1]
    00517    * sum +=  x[srcALen-1] * y[0]
    00518    */
    00519
    00520   /* In this stage the MAC operations are decreased by 1 for every iteration.
    00521      The count variable holds the number of MAC operations performed */
    00522   count = srcBLen - 1u;
    00523
    00524   /* Working pointer of inputA */
    00525   pSrc1 = ((pIn1 + srcALen) - srcBLen) + 1u;
    00526   px = pSrc1;
    00527
    00528   /* Working pointer of inputB */
    00529   py = pIn2;
    00530
    00531   /* -------------------
    00532    * Stage3 process
    00533    * ------------------*/
    00534
    00535   while(blockSize3 > 0u)
    00536   {
    00537     /* Accumulator is made zero for every iteration */
    00538     sum = 0;
    00539
    00540     /* Apply loop unrolling and compute 4 MACs simultaneously. */
    00541     k = count >> 2u;
    00542
    00543     /* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
    00544      ** a second loop below computes MACs for the remaining 1 to 3 samples. */
    00545     while(k > 0u)
    00546     {
    00547       /* Perform the multiply-accumulates */
    00548       /* sum += x[srcALen - srcBLen + 4] * y[3] */
    00549       sum = (q31_t) ((((q63_t) sum << 32) +
    00550                       ((q63_t) * px++ * (*py++))) >> 32);
    00551       /* sum += x[srcALen - srcBLen + 3] * y[2] */
    00552       sum = (q31_t) ((((q63_t) sum << 32) +
    00553                       ((q63_t) * px++ * (*py++))) >> 32);
    00554       /* sum += x[srcALen - srcBLen + 2] * y[1] */
    00555       sum = (q31_t) ((((q63_t) sum << 32) +
    00556                       ((q63_t) * px++ * (*py++))) >> 32);
    00557       /* sum += x[srcALen - srcBLen + 1] * y[0] */
    00558       sum = (q31_t) ((((q63_t) sum << 32) +
    00559                       ((q63_t) * px++ * (*py++))) >> 32);
    00560
    00561       /* Decrement the loop counter */
    00562       k--;
    00563     }
    00564
    00565     /* If the count is not a multiple of 4, compute any remaining MACs here.
    00566      ** No loop unrolling is used. */
    00567     k = count % 0x4u;
    00568
    00569     while(k > 0u)
    00570     {
    00571       /* Perform the multiply-accumulates */
    00572       sum = (q31_t) ((((q63_t) sum << 32) +
    00573                       ((q63_t) * px++ * (*py++))) >> 32);
    00574
    00575       /* Decrement the loop counter */
    00576       k--;
    00577     }
    00578
    00579     /* Store the result in the accumulator in the destination buffer. */
    00580     *pOut = sum << 1;
    00581     /* Destination pointer is updated according to the address modifier, inc */
    00582     pOut += inc;
    00583
    00584     /* Update the inputA and inputB pointers for next MAC calculation */
    00585     px = ++pSrc1;
    00586     py = pIn2;
    00587
    00588     /* Decrement the MAC count */
    00589     count--;
    00590
    00591     /* Decrement the loop counter */
    00592     blockSize3--;
    00593   }
    00594
    00595 }
    00596

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