16Bit Complex Vector Prepare Functions#
 group vect_complex_s16_prepare_api
Defines

vect_complex_s16_add_prepare#
Obtain the output exponent and shifts required for a call to
vect_complex_s16_add()
.The logic for computing the shifts and exponents of
vect_complex_s16_add()
is identical to that forvect_s32_add()
.This macro is provided as a convenience to developers and to make the code more readable.
See also

vect_complex_s16_add_scalar_prepare#
Obtain the output exponent and shifts required for a call to
vect_complex_s16_add_scalar()
.The logic for computing the shifts and exponents of
vect_complex_s16_add_scalar()
is identical to that forvect_s32_add()
.This macro is provided as a convenience to developers and to make the code more readable.
See also
vect_s16_add_prepare()

vect_complex_s16_conj_mul_prepare#
Obtain the output exponent and shifts required for a call to
vect_complex_s16_conj_mul()
.The logic for computing the shifts and exponents of
vect_complex_s16_conj_mul()
is identical to that forvect_complex_s16_mul()
.This macro is provided as a convenience to developers and to make the code more readable.
See also

vect_complex_s16_nmacc_prepare#
Obtain the output exponent and shifts required for a call to vect_complex_s16_nmacc().
The logic for computing the shifts and exponents of
vect_complex_s16_nmacc()
is identical to that forvect_complex_s16_macc()
.This macro is provided as a convenience to developers and to make the code more readable.

vect_complex_s16_conj_macc_prepare#
Obtain the output exponent and shifts required for a call to vect_complex_s16_conj_macc().
The logic for computing the shifts and exponents of
vect_complex_s16_conj_macc()
is identical to that forvect_complex_s16_macc()
.This macro is provided as a convenience to developers and to make the code more readable.

vect_complex_s16_conj_nmacc_prepare#
Obtain the output exponent and shifts required for a call to vect_complex_s16_conj_nmacc().
The logic for computing the shifts and exponents of
vect_complex_s16_conj_nmacc()
is identical to that forvect_complex_s16_macc()
.This macro is provided as a convenience to developers and to make the code more readable.

vect_complex_s16_mag_prepare#
Obtain the output exponent and shifts required for a call to
vect_complex_s16_mag()
.The logic for computing the shifts and exponents of
vect_complex_s16_mag()
is identical to that forvect_complex_s32_mag()
.This macro is provided as a convenience to developers and to make the code more readable.
See also

vect_complex_s16_real_scale_prepare#
Obtain the output exponent and shifts required for a call to vect_complex_s16_real_scale().
The logic for computing the shifts and exponents of
vect_complex_s16_real_scale()
is identical to that forvect_s32_scale()
.This macro is provided as a convenience to developers and to make the code more readable.
See also
vect_s16_scale_prepare()

vect_complex_s16_scale_prepare#
Obtain the output exponent and shifts required for a call to
vect_complex_s16_scale()
.The logic for computing the shifts and exponents of
vect_complex_s16_scale()
is identical to that forvect_complex_s32_mul()
.This macro is provided as a convenience to developers and to make the code more readable.
See also

vect_complex_s16_sub_prepare#
Obtain the output exponent and shifts required for a call to
vect_complex_s16_sub()
.The logic for computing the shifts and exponents of
vect_complex_s16_sub()
is identical to that forvect_s32_add()
.This macro is provided as a convenience to developers and to make the code more readable.
See also
Functions

void vect_complex_s16_macc_prepare(exponent_t *new_acc_exp, right_shift_t *acc_shr, right_shift_t *bc_sat, const exponent_t acc_exp, const exponent_t b_exp, const exponent_t c_exp, const headroom_t acc_hr, const headroom_t b_hr, const headroom_t c_hr)#
Obtain the output exponent and shifts needed by vect_complex_s16_macc().
This function is used in conjunction with vect_complex_s16_macc() to perform an elementwise multiplyaccumlate of complex 16bit BFP vectors.
This function computes
new_acc_exp
andacc_shr
andbc_sat
, which are selected to maximize precision in the resulting accumulator vector without causing saturation of final or intermediate values. Normally the caller will pass these outputs to their corresponding inputs of vect_complex_s16_macc().acc_exp
is the exponent associated with the accumulator mantissa vector \(\bar a\) prior to the operation, whereasnew_acc_exp
is the exponent corresponding to the updated accumulator vector.b_exp
andc_exp
are the exponents associated with the complex input mantissa vectors \(\bar b\) and \(\bar c\) respectively.acc_hr
,b_hr
andc_hr
are the headrooms of \(\bar a\), \(\bar b\) and \(\bar c\) respectively. If the headroom of any of these vectors is unknown, it can be obtained by calling vect_complex_s16_headroom(). Alternatively, the value0
can always be safely used (but may result in reduced precision). Adjusting Output Exponents

If a specific output exponent
desired_exp
is needed for the result (e.g. for emulating fixedpoint arithmetic), theacc_shr
andbc_sat
produced by this function can be adjusted according to the following:// Presumed to be set somewhere exponent_t acc_exp, b_exp, c_exp; headroom_t acc_hr, b_hr, c_hr; exponent_t desired_exp; ... // Call prepare right_shift_t acc_shr, bc_sat; vect_complex_s16_macc_prepare(&acc_exp, &acc_shr, &bc_sat, acc_exp, b_exp, c_exp, acc_hr, b_hr, c_hr); // Modify results right_shift_t mant_shr = desired_exp  acc_exp; acc_exp += mant_shr; acc_shr += mant_shr; bc_sat += mant_shr; // acc_shr and bc_sat may now be used in a call to vect_complex_s16_macc()
When applying the above adjustment, the following conditions should be maintained:
bc_sat >= 0
(bc_sat
is an unsigned rightshift)acc_shr > acc_hr
(Shifting any further left may cause saturation)
It is up to the user to ensure any such modification does not result in saturation or unacceptable loss of precision.
See also
 Parameters:
new_acc_exp – [out] Exponent associated with output mantissa vector \(\bar a\) (after macc)
acc_shr – [out] Signed arithmetic rightshift used for \(\bar a\) in vect_complex_s16_macc()
bc_sat – [out] Unsigned arithmetic rightshift applied to the product of elements \(b_k\) and \(c_k\) in vect_complex_s16_macc()
acc_exp – [in] Exponent associated with input mantissa vector \(\bar a\) (before macc)
b_exp – [in] Exponent associated with input mantissa vector \(\bar b\)
c_exp – [in] Exponent associated with input mantissa vector \(\bar c\)
acc_hr – [in] Headroom of input mantissa vector \(\bar a\) (before macc)
b_hr – [in] Headroom of input mantissa vector \(\bar b\)
c_hr – [in] Headroom of input mantissa vector \(\bar c\)

void vect_complex_s16_mul_prepare(exponent_t *a_exp, right_shift_t *a_shr, const exponent_t b_exp, const exponent_t c_exp, const headroom_t b_hr, const headroom_t c_hr)#
Obtain the output exponent and output shift used by vect_complex_s16_mul() and vect_complex_s16_conj_mul().
This function is used in conjunction with vect_complex_s16_mul() to perform a complex elementwise multiplication of two complex 16bit BFP vectors.
This function computes
a_exp
anda_shr
.a_exp
is the exponent associated with mantissa vector \(\bar a\), and must be chosen to be large enough to avoid overflow when elements of \(\bar a\) are computed. To maximize precision, this function choosesa_exp
to be the smallest exponent known to avoid saturation (see exception below). Thea_exp
chosen by this function is derived from the exponents and headrooms of associated with the input vectors.a_shr
is the shift parameter required by vect_complex_s16_mul() to achieve the chosen output exponenta_exp
.b_exp
andc_exp
are the exponents associated with the input mantissa vectors \(\bar b\) and \(\bar c\) respectively.b_hr
andc_hr
are the headroom of \(\bar b\) and \(\bar c\) respectively. If the headroom of \(\bar b\) or \(\bar c\) is unknown, they can be obtained by calling vect_complex_s16_headroom(). Alternatively, the value0
can always be safely used (but may result in reduced precision). Adjusting Output Exponents

If a specific output exponent
desired_exp
is needed for the result (e.g. for emulating fixedpoint arithmetic), thea_shr
andc_shr
produced by this function can be adjusted according to the following:exponent_t desired_exp = ...; // Value known a priori right_shift_t new_a_shr = a_shr + (desired_exp  a_exp);
When applying the above adjustment, the following conditions should be maintained:
new_a_shr >= 0
Be aware that using smaller values than strictly necessary for
a_shr
can result in saturation, and using larger values may result in unnecessary underflows or loss of precision.
 Notes

Using the outputs of this function, an output mantissa which would otherwise be
INT16_MIN
will instead saturate toINT16_MAX
. This is due to the symmetric saturation logic employed by the VPU and is a hardware feature. This is a corner case which is usually unlikely and results in 1 LSb of error when it occurs.
 Parameters:
a_exp – [out] Exponent associated with output mantissa vector \(\bar a\)
a_shr – [out] Unsigned arithmetic rightshift for \(\bar b\) used by vect_complex_s16_mul()
b_exp – [in] Exponent associated with input mantissa vector \(\bar b\)
c_exp – [in] Exponent associated with input mantissa vector \(\bar c\)
b_hr – [in] Headroom of input mantissa vector \(\bar b\)
c_hr – [in] Headroom of input mantissa vector \(\bar c\)

void vect_complex_s16_real_mul_prepare(exponent_t *a_exp, right_shift_t *a_shr, const exponent_t b_exp, const exponent_t c_exp, const headroom_t b_hr, const headroom_t c_hr)#
Obtain the output exponent and output shift used by vect_complex_s16_real_mul().
This function is used in conjunction with vect_complex_s16_real_mul() to perform a complex elementwise multiplication of a complex 16bit BFP vector by a real 16bit vector.
This function computes
a_exp
anda_shr
.a_exp
is the exponent associated with mantissa vector \(\bar a\), and must be chosen to be large enough to avoid overflow when elements of \(\bar a\) are computed. To maximize precision, this function choosesa_exp
to be the smallest exponent known to avoid saturation (see exception below). Thea_exp
chosen by this function is derived from the exponents and headrooms of associated with the input vectors.a_shr
is the shift parameter required by vect_complex_s16_real_mul() to achieve the chosen output exponenta_exp
.b_exp
andc_exp
are the exponents associated with the input mantissa vectors \(\bar b\) and \(\bar c\) respectively.b_hr
andc_hr
are the headroom of \(\bar b\) and \(\bar c\) respectively. If the headroom of \(\bar b\) or \(\bar c\) is unknown, they can be obtained by calling vect_complex_s16_headroom(). Alternatively, the value0
can always be safely used (but may result in reduced precision). Adjusting Output Exponents

If a specific output exponent
desired_exp
is needed for the result (e.g. for emulating fixedpoint arithmetic), thea_shr
andc_shr
produced by this function can be adjusted according to the following:exponent_t desired_exp = ...; // Value known a priori right_shift_t new_a_shr = a_shr + (desired_exp  a_exp);
When applying the above adjustment, the following conditions should be maintained:
new_a_shr >= 0
Be aware that using smaller values than strictly necessary for
a_shr
can result in saturation, and using larger values may result in unnecessary underflows or loss of precision.
 Notes

Using the outputs of this function, an output mantissa which would otherwise be
INT16_MIN
will instead saturate toINT16_MAX
. This is due to the symmetric saturation logic employed by the VPU and is a hardware feature. This is a corner case which is usually unlikely and results in 1 LSb of error when it occurs.
See also
 Parameters:
a_exp – [out] Exponent associated with output mantissa vector \(\bar a\)
a_shr – [out] Unsigned arithmetic rightshift for \(\bar a\) used by vect_complex_s16_real_mul()
b_exp – [in] Exponent associated with input mantissa vector \(\bar b\)
c_exp – [in] Exponent associated with input mantissa vector \(\bar c\)
b_hr – [in] Headroom of input mantissa vector \(\bar b\)
c_hr – [in] Headroom of input mantissa vector \(\bar c\)

void vect_complex_s16_squared_mag_prepare(exponent_t *a_exp, right_shift_t *a_shr, const exponent_t b_exp, const headroom_t b_hr)#
Obtain the output exponent and input shift used by vect_complex_s16_squared_mag().
This function is used in conjunction with vect_complex_s16_squared_mag() to compute the squared magnitude of each element of a complex 16bit BFP vector.
This function computes
a_exp
anda_shr
.a_exp
is the exponent associated with mantissa vector \(\bar a\), and is be chosen to maximize precision when elements of \(\bar a\) are computed. Thea_exp
chosen by this function is derived from the exponent and headroom associated with the input vector.a_shr
is the shift parameter required by vect_complex_s16_mag() to achieve the chosen output exponenta_exp
.b_exp
is the exponent associated with the input mantissa vector \(\bar b\).b_hr
is the headroom of \(\bar b\). If the headroom of \(\bar b\) is unknown it can be calculated using vect_complex_s16_headroom(). Alternatively, the value0
can always be safely used (but may result in reduced precision). Adjusting Output Exponents

If a specific output exponent
desired_exp
is needed for the result (e.g. for emulating fixedpoint arithmetic), thea_shr
produced by this function can be adjusted according to the following:exponent_t a_exp; right_shift_t a_shr; vect_s16_mul_prepare(&a_exp, &a_shr, b_exp, c_exp, b_hr, c_hr); exponent_t desired_exp = ...; // Value known a priori a_shr = a_shr + (desired_exp  a_exp); a_exp = desired_exp;
When applying the above adjustment, the following condition should be maintained:
a_shr >= 0
Using larger values than strictly necessary for
a_shr
may result in unnecessary underflows or loss of precision.
See also
 Parameters:
a_exp – [out] Output exponent associated with output mantissa vector \(\bar a\)
a_shr – [out] Unsigned arithmetic rightshift for \(\bar a\) used by vect_complex_s16_squared_mag()
b_exp – [in] Exponent associated with input mantissa vector \(\bar b\)
b_hr – [in] Headroom of input mantissa vector \(\bar b\)

vect_complex_s16_add_prepare#