Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Math: Replace exp() function with more accurate and fast version #9786

Open
wants to merge 1 commit into
base: main
Choose a base branch
from
Open

Math: Replace exp() function with more accurate and fast version #9786

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
61 changes: 31 additions & 30 deletions src/include/sof/math/exp_fcn.h
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,8 +1,9 @@
/* SPDX-License-Identifier: BSD-3-Clause
singalsu marked this conversation as resolved.
Show resolved Hide resolved
*
* Copyright(c) 2022 Intel Corporation. All rights reserved.
* Copyright(c) 2022-2025 Intel Corporation.
*
* Author: Shriram Shastry <[email protected]>
* Seppo Ingalsuo <[email protected]>
*
*/
#ifndef __SOFM_EXP_FCN_H__
Expand All @@ -26,40 +27,40 @@

#endif

/* TODO: Is there a MCPS difference */
#define USING_QCONVERT 1
/* Q5.27 int32(round(log((2^31 - 1)/2^20) * 2^27)) */
#define SOFM_EXP_FIXED_INPUT_MAX 1023359037

#if USING_QCONVERT
/* Q8.24 int32(round((log((2^31 - 1)/2^20) * 20 / log(10)) * 2^24)) */
#define SOFM_DB2LIN_INPUT_MAX 1111097957

#include <sof/audio/format.h>
#define SOFM_EXP_FIXED_INPUT_MIN Q_CONVERT_FLOAT(-11.5, 27) /* Q5.27 */
#define SOFM_EXP_FIXED_INPUT_MAX Q_CONVERT_FLOAT(7.6245, 27) /* Q5.27 */
#define SOFM_EXP_TWO_Q27 Q_CONVERT_FLOAT(2.0, 27) /* Q5.27 */
#define SOFM_EXP_MINUS_TWO_Q27 Q_CONVERT_FLOAT(-2.0, 27) /* Q5.27 */
#define SOFM_EXP_ONE_Q20 Q_CONVERT_FLOAT(1.0, 20) /* Q12.20 */
#define SOFM_EXP_MINUS_100_Q24 Q_CONVERT_FLOAT(-100.0, 24) /* Q8.24 */
#define SOFM_EXP_LOG10_DIV20_Q27 Q_CONVERT_FLOAT(0.1151292546, 27) /* Q5.27 */

#else

#define SOFM_EXP_FIXED_INPUT_MIN -1543503872 /* Q_CONVERT_FLOAT(-11.5, 27) */
#define SOFM_EXP_FIXED_INPUT_MAX 1023343067 /* Q_CONVERT_FLOAT(7.6245, 27) */
#define SOFM_EXP_TWO_Q27 268435456 /* Q_CONVERT_FLOAT(2.0, 27) */
#define SOFM_EXP_MINUS_TWO_Q27 -268435456 /* Q_CONVERT_FLOAT(-2.0, 27) */
#define SOFM_EXP_ONE_Q20 1048576 /* Q_CONVERT_FLOAT(1.0, 20) */
#define SOFM_EXP_MINUS_100_Q24 -1677721600 /* Q_CONVERT_FLOAT(-100.0, 24) */
#define SOFM_EXP_LOG10_DIV20_Q27 15452387 /* Q_CONVERT_FLOAT(0.1151292546, 27) */
/**
* Calculates exponent function exp(x) = e^x with accurate and efficient technique that
* includes range reduction operations, approximation with Taylor series, and reconstruction
* operations to compensate the range reductions.
* @param x The input argument as Q4.28 from -8 to +8
* @return The calculated e^x value as Q13.19 from 3.3546e-04 to 2981.0
*/
int32_t sofm_exp_approx(int32_t x);

#endif
/**
* Calculated exponent function exp(x) = e^x by using sofm_exp_approx(). The input range for
* large arguments is internally reduced to -8 to +8 with rule exp(x) = exp(x/2) * exp(x/2)
* and reconstructed back. This function is essentially a wrapper for compatibility with
* existing usage of exp() function and Q-format choice. Note that the return value saturates
* to INT32_MAX with input arguments larger than 7.6246.
* @param x The input argument as Q5.27 from -16 to +16
* @return The calculated e^x value as Q12.20
*/
int32_t sofm_exp_fixed(int32_t x);

#define SOFM_EXP_BIT_MASK_LOW_Q27P5 0x0000000008000000
#define SOFM_EXP_BIT_MASK_Q62P2 0x4000000000000000LL
#define SOFM_EXP_QUOTIENT_SCALE 0x40000000
#define SOFM_EXP_TERMS_Q23P9 0x800000
#define SOFM_EXP_LSHIFT_BITS 0x2000

int32_t sofm_exp_int32(int32_t x);
int32_t sofm_exp_fixed(int32_t x);
/**
* Converts a decibels value to liner amplitude lin = 10^(db/20) value with optimized
* equation exp(db * log(10)/20). Note that due to range limitation of sofm_exp_fixed()
* the output saturates to maximum with about +66 dB input.
* @param db Decibels value in Q8.24 format, from -128 to +66.226
* @return Linear value in Q12.20 format, from 3.9811e-07 to 2048
*/
int32_t sofm_db2lin_fixed(int32_t db);

#endif /* __SOFM_EXP_FCN_H__ */
Loading
Loading