cyanreg / latency.txt

Last active December 13, 2020 15:58 — forked from jboner/latency.txt

Latency Numbers Every Programmer Should Know

	Latency Comparison Numbers (~2012)
	----------------------------------
	L1 cache reference 0.5 ns
	Branch mispredict 5 ns
	L2 cache reference 7 ns 14x L1 cache
	Mutex lock/unlock 25 ns
	Main memory reference 100 ns 20x L2 cache, 200x L1 cache
	Compress 1K bytes with Zippy 3,000 ns 3 us
	Send 1K bytes over 1 Gbps network 10,000 ns 10 us
	Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD

cyanreg / fft8.c

Last active January 27, 2021 02:01

8-point FFT (permuted input)

cyanreg / fft4.c

Last active March 7, 2021 21:15

4-point FFT

	static void fft4(void s, FFTComplex z, FFTComplex *temp)
	{
	FFTSample r1 = z[0].re - z[2].re;
	FFTSample r2 = z[0].im - z[2].im;
	FFTSample r3 = z[1].re - z[3].re;
	FFTSample r4 = z[1].im - z[3].im;
	/* r5-r8 second transform */

	FFTSample t1 = z[0].re + z[2].re;
	FFTSample t2 = z[0].im + z[2].im;

cyanreg / fft16.c

Last active March 3, 2021 11:02

16-point FFT

	// from https://gist.github.com/cyanreg/665b9c79cbe51df9296a969257f2a16c
	static void fft4(FFTComplex *z)
	{
	FFTSample r1 = z[0].re - z[4].re;
	FFTSample r2 = z[0].im - z[4].im;
	FFTSample r3 = z[1].re - z[5].re;
	FFTSample r4 = z[1].im - z[5].im;
	/* r5-r8 second transform */

	FFTSample t1 = z[0].re + z[4].re;

cyanreg / fft8_double.c

Created March 9, 2021 03:17

8-point FFT (2x at a time)

	static void fft8(void s, FFTComplex z, FFTComplex *temp)
	{
	FFTSample r1 = z[0].re - z[4].re;
	FFTSample r2 = z[0].im - z[4].im;
	FFTSample r3 = z[1].re - z[5].re;
	FFTSample r4 = z[1].im - z[5].im;

	FFTSample j1 = z[2].re - z[6].re;
	FFTSample j2 = z[2].im - z[6].im;
	FFTSample j3 = z[3].re - z[7].re;

cyanreg / fft_split_radix_recombine.c

Last active April 2, 2021 14:47

Split-Radix recombine loop

	#define BF(x, y, a, b) \
	do { \
	x = (a) - (b); \
	y = (a) + (b); \
	} while (0)

	#define BUTTERFLIES_MIX(a0,a1,a2,a3, P1, P2, P5, P6) \
	do { \
	r0=a0.re; \
	i0=a0.im; \

cyanreg / qmf_forward.c

Created March 13, 2021 19:27

Forward QMF

	void forward_qmf(float out_low, float out_high, float delay, const float in,
	int samples, int delay_samples)
	{
	memcpy(delay, delay + samples, delay_samples * sizeof(float));
	memcpy(delay + delay_samples, in, samples * sizeof(float));

	for (int i = 0; i < samples; i += 2) {
	float low = 0.0f, high = 0.0f;

	/* Can be done via float_dsp */

cyanreg / tx_float.asm

Last active April 20, 2021 23:59

libavutil/tx x86 assembly

	;******************************************************************************
	;* Copyright (c) Lynne
	;*
	;* This file is part of FFmpeg.
	;*
	;* FFmpeg is free software; you can redistribute it and/or
	;* modify it under the terms of the GNU Lesser General Public
	;* License as published by the Free Software Foundation; either
	;* version 2.1 of the License, or (at your option) any later version.
	;*

cyanreg / tx_float_init.c

Created April 19, 2021 13:10

FFmpeg transform debugging code

	/*
	* This file is part of FFmpeg.
	*
	* FFmpeg is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2.1 of the License, or (at your option) any later version.
	*
	* FFmpeg is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of

cyanreg / ANSI.md

Created August 9, 2021 10:44 — forked from fnky/ANSI.md

ANSI Escape Codes

ANSI Escape Sequences

Standard escape codes are prefixed with Escape:

Lynne cyanreg