pervognsen

Let's say you have to perform a 4-way case analysis and are given a choice between cascaded 2-way branches or a single 4-way branch.

What's the difference in branch misprediction penalties, assuming the 4 cases are random?

Denote the branch penalty by x (which is 15-20 cycles on Sky Lake according to Agner Fog).

With the 4-way branch, the worst-case branch penalty is x. The expected branch penalty is 3/4 x: there's a 3/4 chance of x penalty.

pervognsen

// x64 encoding

enum Reg {
    RAX, RCX, RDX, RBX, RSP, RBP, RSI, RDI,
    R8,  R9,  R10, R11, R12, R13, R14, R15,
};

enum XmmReg {
    XMM0, XMM1, XMM2,  XMM3,  XMM4,  XMM5,  XMM6,  XMM7,
    XMM8, XMM9, XMM10, XMM11, XMM12, XMM13, XMM14, XMM15,

sereprz

import datetime
import pickle
import os.path
from googleapiclient.discovery import build
from google_auth_oauthlib.flow import InstalledAppFlow
from google.auth.transport.requests import Request

SCOPES = 'https://www.googleapis.com/auth/calendar.events'

def main():

pervognsen

#if _WIN32
// measure the time in seconds to run f(). doubles will retain nanosecond precision.
template<typename F>
double timeit(F f) {
    LARGE_INTEGER freq;
    QueryPerformanceFrequency(&freq);
    LARGE_INTEGER start;
    QueryPerformanceCounter(&start);
    f();
    LARGE_INTEGER end;

pervognsen

def blocks(A, block_size=(1, 1)):
    i, j = block_size
    while len(A):
        yield A[:i, :j], A[:i, j:], A[i:, :j], A[i:, j:]
        A = A[i:, j:]

# 2400 ms for 1000x1000 matrix (~0.4 GFLOPS). Equivalent C code is only twice as fast (~0.8 GFLOPS).
# The reason the C code isn't much faster is that it's an O(n^3) algorithm and most of the time is spent in
# the O(n^2) kernel routine for the outer product in A11[:] -= A10 @ A10.T. Even if we posit that Python
# is 1000x slower than C for the outer loop, that's still 1000n + n^3 vs n^3, which is negligible for n = 1000.

rygorous

// ---- triangle rasterizer

#define SUBPIXEL_SHIFT  8
#define SUBPIXEL_SCALE  (1 << SUBPIXEL_SHIFT)

static RADINLINE S64 det2x2(S32 a, S32 b, S32 c, S32 d)
{
   S64 r = (S64) a*d - (S64) b*c;
   return r >> SUBPIXEL_SHIFT;
}

mmalex

TLDR: if you've got a bunch of delays in series, for example all-pass filters in a reverb, put them all in a single big buffer and let them crawl over each other for a perf win!

recently I was fiddling around with my hobby reverb code, in preparation for porting it onto a smaller/slower CPU. I'd implemented a loop-of-allpass filters type reverb, just like everybody else, and indeed, I basically had the classic 'OOP'ish abstraction of an 'allpass' struct that was, say, 313 samples long, and... did an allpass. on its own little float buffer[313]. (well, short integer, not float, but thats not relevant) I'll write out the code in a moment.

but then I was browsing the internet one night, as you do, and stumbled on this old post by Sean Costello of Valhalla DSP fame - noting the sad passing of Alesis founder and general all-round DSP legend, Keith Barr. https://valhalladsp.com/2010/08/25/rip-keith-barr/

It's worth a read just for his wonderful anecdote about the birth of the midiverb - which spawned the thou

pixelsnafu

Volumetric Clouds Resources List

1. A. Schneider, "Real-Time Volumetric Cloudscapes," in GPU Pro 7: Advanced Rendering Techniques, 2016, pp. 97-127. (Follow up presentations here, and here.)

2. S. Hillaire, "Physically Based Sky, Atmosphere and Cloud Rendering in Frostbite" in Physically Based Shading in Theory and Practice course, SIGGRAPH 2016. [video] [course notes] [scatter integral shadertoy]

3. [R. Högfeldt, "Convincing Cloud Rendering – An Implementation of Real-Time Dynamic Volumetric Clouds in Frostbite"](https://odr.chalmers.se/hand

Jolg42

macOS

Steps

• What we want is to get a Developer Id https://developer.apple.com/developer-id/ to be able to sign the binaries for distribution.
• The company needs to get an Apple Developer Account Membership for macOS for $99/y https://developer.apple.com/programs/enroll/
• Apple needs a A D-U-N-S® Number to register the account, the person doing the registration will need to get in touch with somebody that knows the legal part.
• The registration could take a couple days
• When done, a certificate can be created for signing, you'll need to sync it with Xcode.
• Now the binary can be signed, and the signature can be verified.

wtaysom

Hello Friends,

This elf begging to climb onto the web for Christmas began as a personal email, a review of Paul Graham's little Lisp Bel. He sprouted arms, legs, and in gingerstyle ran away. Arms for symbols, legs for conses: these primitives are the mark a Lisp — even more so than the parenthesis. What do we get when we remove these foundation stones: naming and pairing?

No pairs. No cons. No structure. Unordered. Chaos. Eve, a beautifully incomplete aspect oriented triple store. No need for legs when you can effortlessly transport to your destination. Lazy. Pure. Here and now, a retrospective.

No symbols. No names. No variables. Combinators. Forth. No need for arms when you can effortlessly push and pop your stack. No words. A world without words. Virtual worlds. Virtual reality. Space. Time. Motion. Action. Kinetic Programming, a proposal.

I apologize in advance. Checking my pocketwatch, I see I haven't t