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https://github.com/jart/cosmopolitan.git
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9e3e985ae5
Here's some screenshots of an emulator tui program that was compiled on Linux, then scp'd it to Windows, Mac, and FreeBSD. https://justine.storage.googleapis.com/blinkenlights-cmdexe.png https://justine.storage.googleapis.com/blinkenlights-imac.png https://justine.storage.googleapis.com/blinkenlights-freebsd.png https://justine.storage.googleapis.com/blinkenlights-lisp.png How is this even possible that we have a nontrivial ui binary that just works on Mac, Windows, Linux, and BSD? Surely a first ever achievement. Fixed many bugs. Bootstrapped John McCarthy's metacircular evaluator on bare metal in half the size of Altair BASIC (about 2.5kb) and ran it in emulator for fun and profit.
113 lines
4.5 KiB
C
113 lines
4.5 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "dsp/core/q.h"
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#include "libc/assert.h"
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#include "libc/dce.h"
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#include "libc/limits.h"
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#include "libc/macros.h"
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#include "libc/math.h"
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#include "libc/str/str.h"
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/**
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* Precomputes integers that can replace floating-point operands.
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*
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* “G-d made the integers, all else is the work of man.
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* — Leopold Kronecker
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*
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* This function shifts the decimal point to the left:
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*
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* 𝑛ᵢ ← ROUND[𝑐ᵢ × 2ᵐ] + φᵢ
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*
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* With extra effort to compute φ which is normally all zeroes but gives
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* us better rounding when it isn't. It's assumed optimized coefficients
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* will be used like this:
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*
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* (Σᵢ𝑥ᵢ𝑛ᵢ + 2⁽ᵐ⁻¹⁾) / 2ᵐ where 𝑥∈[𝐿,𝐻] and 𝑖∈[0,6)
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*
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* Intended to compute this
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*
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* ROUND[Σᵢ𝑥ᵢ𝑐ᵢ]
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*
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* As accurately or approximately as you want it to be. Popular scaling
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* factors are 7, 15, 16, 22, and 31. Building this code under MODE=tiny
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* will DCE the math.
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*
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* @param N receives optimized integers
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* @param C provides ideal coefficients
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* @param M is log₂ scaling factor, e.g. 7
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* @param L is minimum input data size, e.g. 0
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* @param H is maximum input data size, e.g. 255
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* @return sum of errors for all inputs
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* @see en.wikipedia.org/wiki/Binary_scaling
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* @see o/tool/build/coefficients.com
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* @cost ~300ns
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*/
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long GetIntegerCoefficients(long N[static 6], const double C[static 6], long M,
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long L, long H) {
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int i;
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int j[6], J[6];
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int O[6] = {0};
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int S[3] = {0, -1, +1};
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double R[6], K[6], D[6], HM, HL, least, error;
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least = 1;
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HM = 1L << M;
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HL = H - L + 1;
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assert(H >= L);
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assert(HL <= HM);
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for (i = 0; i < 6; ++i) {
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least *= HL;
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if (fabs(C[i]) > DBL_MIN) {
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J[i] = ARRAYLEN(S);
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R[i] = C[i] * HM;
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K[i] = rint(R[i]);
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N[i] = K[i];
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} else {
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J[i] = 1;
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R[i] = 0;
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K[i] = 0;
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N[i] = 0;
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}
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}
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if (!NoDebug() && least > 1) {
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for (j[0] = 0; j[0] < J[0]; ++j[0]) {
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for (j[1] = 0; j[1] < J[1]; ++j[1]) {
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for (j[2] = 0; j[2] < J[2]; ++j[2]) {
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for (j[3] = 0; j[3] < J[3]; ++j[3]) {
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for (j[4] = 0; j[4] < J[4]; ++j[4]) {
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for (j[5] = 0; j[5] < J[5]; ++j[5]) {
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for (i = 0; i < ARRAYLEN(J); ++i) {
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D[i] = S[j[i]] + K[i] - R[i];
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}
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if ((error = DifferSumSq(D, L, H) / HM) < least) {
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least = error;
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memcpy(O, j, sizeof(j));
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}
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}
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}
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}
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}
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}
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}
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for (i = 0; i < 6; ++i) {
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N[i] += S[O[i]];
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}
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}
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return lround(least);
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}
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