Robert Allan James
36389e9d4a
Adds q48_reduce_angle() (range-reduce a signed Q48.16 angle into [-PI_Q48, PI_Q48] via one integer division plus a bounded fix-up loop) and q48_sin_approx/q48_cos_approx (Taylor series, terms n=3,5,7,9,11 for sin and n=2,4,6,8,10 for cos, early exit below 10). Q.SIN/Q.COS registered as FORTH words in q48_words.c, same pattern as Q.LOG/Q.EXP/Q.SQRT. Found mid-implementation: this codebase has two independent Q48.16 implementations -- src/word_source/q48_16_words.c (hosted/vendored) and src/starkernel/math/q48_16.c (kernel-only; the kernel build does not compile the former at all). The hosted build linked fine after the first pass; the kernel build failed with undefined references until the same two functions were added to both .c files and both q48_16.h headers (include/q48_16.h and include/starkernel/q48_16.h). Not fixed at the root -- Q.LOG/Q.EXP/Q.SQRT already had this same four-file duplication, unremarked until now -- just navigated correctly for this item. Verified live on amd64 via serial injection: sin/cos at 0, +-pi/2, pi, and 3pi (range-reduction across multiple turns) all match expected values within Taylor-series truncation error (<0.2%). All three architectures boot clean to ok> with the DoE completing; dict_hash identical across all three (0x291a660b05fa7b52). FABRIC.md item 4.3.3a marked done with full acceptance evidence.
164 lines
4.5 KiB
C
164 lines
4.5 KiB
C
/*
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StarForth — Steady-State Virtual Machine Runtime
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Copyright (c) 2023–2025 Robert A. James
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All rights reserved.
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This file is part of the StarForth project.
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Licensed under the StarForth License, Version 1.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at:
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https://github.com/star.4th@proton.me/StarForth/LICENSE.txt
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This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
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express or implied, including but not limited to the warranties of
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merchantability, fitness for a particular purpose, and noninfringement.
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See the License for the specific language governing permissions and
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limitations under the License.
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StarForth — Steady-State Virtual Machine Runtime
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Copyright (c) 2023–2025 Robert A. James
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All rights reserved.
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This file is part of the StarForth project.
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Licensed under the StarForth License, Version 1.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at:
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https://github.com/star.4th@proton.me/StarForth/LICENSE.txt
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This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
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express or implied, including but not limited to the warranties of
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merchantability, fitness for a particular purpose, and noninfringement.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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/**
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* q48_16.h - Q48.16 Fixed-Point Arithmetic for StarKernel
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*
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* Format: uint64_t with fixed decimal point after bit 15
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* - Bits 0-15: Fractional part (1/65536 resolution)
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* - Bits 16-63: Integer part (up to 2^48-1)
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*
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* Example: 0x00010000 = 1.0, 0x00018000 = 1.5
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*
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* All operations are integer-only. NO FLOATING-POINT.
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*/
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#ifndef STARKERNEL_Q48_16_H
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#define STARKERNEL_Q48_16_H
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/* If the hosted-VM q48_16.h is already pulled in (e.g. via inference_engine.h),
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* skip the duplicate static-inline definitions — clang rejects them as errors. */
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#ifndef Q48_16_H
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#include <stdint.h>
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typedef uint64_t q48_16_t;
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/* Q48.16 representation of 1.0 */
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#define Q48_ONE ((q48_16_t)0x10000ULL)
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/* ============================================================================
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* Core Arithmetic Operations
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* ============================================================================ */
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/*
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* Multiply two Q48.16 values: (a * b) >> 16
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*/
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q48_16_t q48_mul(q48_16_t a, q48_16_t b);
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/*
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* Divide two Q48.16 values: (a << 16) / b
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* Returns 0 if b == 0.
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*/
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q48_16_t q48_div(q48_16_t a, q48_16_t b);
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/**
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* Add two Q48.16 values
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*/
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static inline q48_16_t q48_add(q48_16_t a, q48_16_t b) {
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return a + b;
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}
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/**
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* Subtract two Q48.16 values
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*/
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static inline q48_16_t q48_sub(q48_16_t a, q48_16_t b) {
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return a - b;
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}
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/**
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* Absolute value of Q48.16 (treats as unsigned, so just returns a)
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*/
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static inline q48_16_t q48_abs(q48_16_t a) {
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return a; /* Q48.16 is unsigned; for signed use, caller handles */
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}
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/* ============================================================================
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* Conversion Operations
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* ============================================================================ */
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/**
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* Convert unsigned 64-bit integer to Q48.16: u << 16
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*/
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static inline q48_16_t q48_from_u64(uint64_t u) {
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return u << 16;
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}
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/**
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* Convert Q48.16 to unsigned 64-bit integer (truncate fractional): q >> 16
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*/
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static inline uint64_t q48_to_u64(q48_16_t q) {
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return q >> 16;
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}
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/* ============================================================================
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* Approximation Operations (Integer-Only)
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* ============================================================================ */
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/*
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* Approximate natural logarithm in Q48.16 (integer-only)
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* Input: x in Q48.16 format (x > 0)
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* Output: ln(x) in Q48.16 format
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*/
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q48_16_t q48_log_approx(q48_16_t x);
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/*
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* Approximate exponential e^x in Q48.16 (integer-only)
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* Input: q in Q48.16 format
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* Output: e^q in Q48.16 format
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*/
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q48_16_t q48_exp_approx(q48_16_t q);
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/*
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* Approximate square root in Q48.16 (integer-only, Newton-Raphson)
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* Input: q in Q48.16 format
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* Output: sqrt(q) in Q48.16 format
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*/
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q48_16_t q48_sqrt_approx(q48_16_t q);
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/*
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* Approximate sin(q) in Q48.16 (integer-only, Taylor series, radians)
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* Input: q in Q48.16 format (any magnitude)
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* Output: sin(q) in Q48.16 format
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*/
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q48_16_t q48_sin_approx(q48_16_t q);
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/*
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* Approximate cos(q) in Q48.16 (integer-only, Taylor series, radians)
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* Input: q in Q48.16 format (any magnitude)
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* Output: cos(q) in Q48.16 format
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*/
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q48_16_t q48_cos_approx(q48_16_t q);
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#endif /* !Q48_16_H */
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#endif /* STARKERNEL_Q48_16_H */
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