csd Namespace Reference

Classes
class	invalid_csd_format
	Exception thrown when invalid CSD characters are encountered. More...
struct	MultiplierSpec
	Specification for a single CSD multiplier coefficient. More...

Functions
auto	to_csd (double decimal_value, int places) -> std::string
auto	to_csd_i (int decimal_value) -> std::string
auto	to_csdnnz (double decimal_value, unsigned int nnz) -> std::string
	Convert a floating-point number to CSD with limited non-zero digits.
auto	to_csdnnz_i (int decimal_value, unsigned int nnz) -> std::string
	Convert an integer to CSD with limited non-zero digits.
CONSTEXPR14 auto	to_decimal_using_switch (const char *csd) -> double
CONSTEXPR14 auto	to_decimal_integral (const char *&csd) -> int
	Convert the integral part of a CSD string to a decimal.
CONSTEXPR14 auto	to_decimal_fractional (const char *csd) -> double
	Convert the fractional part of a CSD string to a decimal.
CONSTEXPR14 auto	to_decimal (const char *csd) -> double
	Convert the CSD string to a decimal.
CONSTEXPR14 auto	to_decimal_i (const char *csd) -> int
	Convert CSD string to integer.
auto	generate_csd_multiplier (const std::string &csd_str, int input_width, int max_power) -> std::string
	Generate Verilog code for a single CSD multiplier module.
auto	generate_csd_multipliers (const std::vector< MultiplierSpec > &coeffs, const std::string &module_name="csd_filter") -> std::string
	Generate Verilog for multiple CSD multipliers with cross-CSE.
auto	longest_repeated_substring (const char *sv, size_t len) -> std::string
	Find the longest repeated non-overlapping substring.
void	log_with_spdlog (const std::string &message)
	Log a message using spdlog.

Variables
constexpr int	MAX_DECIMAL_PLACES = 20
	Maximum number of decimal places supported by CSD conversion.
constexpr unsigned int	MIN_NONZERO_DIGITS = 1
	Minimum value for non-zero digit count in CSDNNZ functions.

Function Documentation

generate_csd_multiplier()

auto csd::generate_csd_multiplier	(	const std::string &	csd_str,
		int	input_width,
		int	max_power
	)		-> std::string

Generate Verilog code for a single CSD multiplier module.

Converts a Canonical Signed Digit (CSD) string into a synthesizable Verilog module that performs constant multiplication using shifts and additions/subtractions.

Parameters

[in]	csd_str	CSD string using '+', '-', '0' (e.g. "+00-00+0+")
[in]	input_width	Bit width of the input signal x
[in]	max_power	Highest power of two in the CSD (must be len(csd)-1)

Returns

Verilog module code as a string

Exceptions

std::invalid_argument

if csd_str length doesn't match max_power+1 or if the string contains characters other than '+', '-', '0'

generate_csd_multipliers()

auto csd::generate_csd_multipliers	(	const std::vector< MultiplierSpec > &	coeffs,
		const std::string &	module_name = "csd_filter"
	)		-> std::string

Generate Verilog for multiple CSD multipliers with cross-CSE.

When the same CSD substring appears in multiple coefficients, a shared sub-expression wire is created - reducing total adder count across the entire filter.

All coefficients must share the same input_width and max_power so that the same bit position encodes the same power of two.

Parameters

[in]	coeffs	List of coefficient specifications
[in]	module_name	Name for the generated Verilog module

Returns

Verilog module code

Exceptions

std::invalid_argument

on validation failure or width mismatch

log_with_spdlog()

void csd::log_with_spdlog

(

const std::string &

message

)

Log a message using spdlog.

This function logs a message using the spdlog library. It provides a simple interface for logging messages throughout the csd library without exposing the full spdlog API.

Parameters

[in]

message

The message to log