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Rev	Author	Line No.	Line
2	mjames	1	/* ----------------------------------------------------------------------
		2	* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
		3	*
		4	* $Date: 19. March 2015
		5	* $Revision: V.1.4.5
		6	*
		7	* Project: CMSIS DSP Library
		8	* Title: arm_mat_mult_fast_q31.c
		9	*
		10	* Description: Q31 matrix multiplication (fast variant).
		11	*
		12	* Target Processor: Cortex-M4/Cortex-M3
		13	*
		14	* Redistribution and use in source and binary forms, with or without
		15	* modification, are permitted provided that the following conditions
		16	* are met:
		17	* - Redistributions of source code must retain the above copyright
		18	* notice, this list of conditions and the following disclaimer.
		19	* - Redistributions in binary form must reproduce the above copyright
		20	* notice, this list of conditions and the following disclaimer in
		21	* the documentation and/or other materials provided with the
		22	* distribution.
		23	* - Neither the name of ARM LIMITED nor the names of its contributors
		24	* may be used to endorse or promote products derived from this
		25	* software without specific prior written permission.
		26	*
		27	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
		28	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
		29	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
		30	* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
		31	* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
		32	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
		33	* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
		34	* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
		35	* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
		36	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
		37	* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
		38	* POSSIBILITY OF SUCH DAMAGE.
		39	* -------------------------------------------------------------------- */
		40
		41	#include "arm_math.h"
		42
		43	/**
		44	* @ingroup groupMatrix
		45	*/
		46
		47	/**
		48	* @addtogroup MatrixMult
		49	* @{
		50	*/
		51
		52	/**
		53	* @brief Q31 matrix multiplication (fast variant) for Cortex-M3 and Cortex-M4
		54	* @param[in] *pSrcA points to the first input matrix structure
		55	* @param[in] *pSrcB points to the second input matrix structure
		56	* @param[out] *pDst points to output matrix structure
		57	* @return The function returns either
		58	* <code>ARM_MATH_SIZE_MISMATCH</code> or <code>ARM_MATH_SUCCESS</code> based on the outcome of size checking.
		59	*
		60	* @details
		61	* <b>Scaling and Overflow Behavior:</b>
		62	*
		63	* \par
		64	* The difference between the function arm_mat_mult_q31() and this fast variant is that
		65	* the fast variant use a 32-bit rather than a 64-bit accumulator.
		66	* The result of each 1.31 x 1.31 multiplication is truncated to
		67	* 2.30 format. These intermediate results are accumulated in a 32-bit register in 2.30
		68	* format. Finally, the accumulator is saturated and converted to a 1.31 result.
		69	*
		70	* \par
		71	* The fast version has the same overflow behavior as the standard version but provides
		72	* less precision since it discards the low 32 bits of each multiplication result.
		73	* In order to avoid overflows completely the input signals must be scaled down.
		74	* Scale down one of the input matrices by log2(numColsA) bits to
		75	* avoid overflows, as a total of numColsA additions are computed internally for each
		76	* output element.
		77	*
		78	* \par
		79	* See <code>arm_mat_mult_q31()</code> for a slower implementation of this function
		80	* which uses 64-bit accumulation to provide higher precision.
		81	*/
		82
		83	arm_status arm_mat_mult_fast_q31(
		84	const arm_matrix_instance_q31 * pSrcA,
		85	const arm_matrix_instance_q31 * pSrcB,
		86	arm_matrix_instance_q31 * pDst)
		87	{
		88	q31_t pIn1 = pSrcA->pData; / input data matrix pointer A */
		89	q31_t pIn2 = pSrcB->pData; / input data matrix pointer B */
		90	q31_t pInA = pSrcA->pData; / input data matrix pointer A */
		91	// q31_t pSrcB = pSrcB->pData; / input data matrix pointer B */
		92	q31_t pOut = pDst->pData; / output data matrix pointer */
		93	q31_t px; / Temporary output data matrix pointer */
		94	q31_t sum; /* Accumulator */
		95	uint16_t numRowsA = pSrcA->numRows; /* number of rows of input matrix A */
		96	uint16_t numColsB = pSrcB->numCols; /* number of columns of input matrix B */
		97	uint16_t numColsA = pSrcA->numCols; /* number of columns of input matrix A */
		98	uint16_t col, i = 0u, j, row = numRowsA, colCnt; /* loop counters */
		99	arm_status status; /* status of matrix multiplication */
		100	q31_t inA1, inA2, inA3, inA4, inB1, inB2, inB3, inB4;
		101
		102	#ifdef ARM_MATH_MATRIX_CHECK
		103
		104
		105	/* Check for matrix mismatch condition */
		106	if((pSrcA->numCols != pSrcB->numRows) \|\|
		107	(pSrcA->numRows != pDst->numRows) \|\| (pSrcB->numCols != pDst->numCols))
		108	{
		109	/* Set status as ARM_MATH_SIZE_MISMATCH */
		110	status = ARM_MATH_SIZE_MISMATCH;
		111	}
		112	else
		113	#endif /* #ifdef ARM_MATH_MATRIX_CHECK */
		114
		115	{
		116	/* The following loop performs the dot-product of each row in pSrcA with each column in pSrcB */
		117	/* row loop */
		118	do
		119	{
		120	/* Output pointer is set to starting address of the row being processed */
		121	px = pOut + i;
		122
		123	/* For every row wise process, the column loop counter is to be initiated */
		124	col = numColsB;
		125
		126	/* For every row wise process, the pIn2 pointer is set
		127	** to the starting address of the pSrcB data */
		128	pIn2 = pSrcB->pData;
		129
		130	j = 0u;
		131
		132	/* column loop */
		133	do
		134	{
		135	/* Set the variable sum, that acts as accumulator, to zero */
		136	sum = 0;
		137
		138	/* Initiate the pointer pIn1 to point to the starting address of pInA */
		139	pIn1 = pInA;
		140
		141	/* Apply loop unrolling and compute 4 MACs simultaneously. */
		142	colCnt = numColsA >> 2;
		143
		144
		145	/* matrix multiplication */
		146	while(colCnt > 0u)
		147	{
		148	/* c(m,n) = a(1,1)b(1,1) + a(1,2) b(2,1) + .... + a(m,p)b(p,n) /
		149	/* Perform the multiply-accumulates */
		150	inB1 = *pIn2;
		151	pIn2 += numColsB;
		152
		153	inA1 = pIn1[0];
		154	inA2 = pIn1[1];
		155
		156	inB2 = *pIn2;
		157	pIn2 += numColsB;
		158
		159	inB3 = *pIn2;
		160	pIn2 += numColsB;
		161
		162	sum = (q31_t) ((((q63_t) sum << 32) + ((q63_t) inA1 * inB1)) >> 32);
		163	sum = (q31_t) ((((q63_t) sum << 32) + ((q63_t) inA2 * inB2)) >> 32);
		164
		165	inA3 = pIn1[2];
		166	inA4 = pIn1[3];
		167
		168	inB4 = *pIn2;
		169	pIn2 += numColsB;
		170
		171	sum = (q31_t) ((((q63_t) sum << 32) + ((q63_t) inA3 * inB3)) >> 32);
		172	sum = (q31_t) ((((q63_t) sum << 32) + ((q63_t) inA4 * inB4)) >> 32);
		173
		174	pIn1 += 4u;
		175
		176	/* Decrement the loop counter */
		177	colCnt--;
		178	}
		179
		180	/* If the columns of pSrcA is not a multiple of 4, compute any remaining output samples here.
		181	** No loop unrolling is used. */
		182	colCnt = numColsA % 0x4u;
		183
		184	while(colCnt > 0u)
		185	{
		186	/* c(m,n) = a(1,1)b(1,1) + a(1,2) b(2,1) + .... + a(m,p)b(p,n) /
		187	/* Perform the multiply-accumulates */
		188	sum = (q31_t) ((((q63_t) sum << 32) +
		189	((q63_t) * pIn1++ * (*pIn2))) >> 32);
		190	pIn2 += numColsB;
		191
		192	/* Decrement the loop counter */
		193	colCnt--;
		194	}
		195
		196	/* Convert the result from 2.30 to 1.31 format and store in destination buffer */
		197	*px++ = sum << 1;
		198
		199	/* Update the pointer pIn2 to point to the starting address of the next column */
		200	j++;
		201	pIn2 = pSrcB->pData + j;
		202
		203	/* Decrement the column loop counter */
		204	col--;
		205
		206	} while(col > 0u);
		207
		208	/* Update the pointer pInA to point to the starting address of the next row */
		209	i = i + numColsB;
		210	pInA = pInA + numColsA;
		211
		212	/* Decrement the row loop counter */
		213	row--;
		214
		215	} while(row > 0u);
		216
		217	/* set status as ARM_MATH_SUCCESS */
		218	status = ARM_MATH_SUCCESS;
		219	}
		220	/* Return to application */
		221	return (status);
		222	}
		223
		224	/**
		225	* @} end of MatrixMult group
		226	*/

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