nelhage

[nelhage@monolithique:~/code/alexbench]$ clang-11 -O1 -S -c -emit-llvm overflow_2.c
[nelhage@monolithique:~/code/alexbench]$ opt-11 --opt-bisect-limit=137 -O2 -S overflow_2.ll 2>/dev/null | opt-11 -O2 -S -o overflow_2_opt.ll
[nelhage@monolithique:~/code/alexbench]$ cat overflow_2_opt.ll 
; ModuleID = '<stdin>'
source_filename = "overflow_2.c"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

; Function Attrs: nofree nounwind uwtable
define dso_local { i8*, i64 } @f1_overflow() local_unnamed_addr #0 {

nelhage

[package]
name = "f"
version = "0.1.0"
authors = ["Alex Gaynor <alex.gaynor@gmail.com>"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
packed_simd = "0.3"

nelhage

       │       intrinsics::move_val_init(&mut *dst, src)                                                                                                  ▒
  0.90 │         lea       (%rsi,%rsi,4),%rcx                                                                                                             ▒
  0.05 │         shl       $0x4,%rcx                                                                                                                      ▒
  0.11 │         mov       0xb8(%rsp),%rdx                                                                                                                ▒
  0.80 │         mov       %rdx,(%rax,%rcx,1)                                                                                                             ▒
  1.66 │         movaps    0xd0(%rsp),%xmm0                                                                                                               ▒
 11.08 │         movups    %xmm0,0x8(%rax,%rcx,1)                                       

nelhage

My approach:

• Let's use "cost" as a proxy for CO2 emissions, because within an order of magnitude I expect $1 on gas emits as much CO2 as $1 of power for a server, and I believe the bulk of the ongoing cost of operating a server is power budget.
• Lifetime cost of a gas for a car: Let's estimate 100,000 miles, and 20 mpg and $4/gal. That gives us 5,000 gal and $20,000 in lifetime gas cost for a car. These numbers all feel pessimistic so we're maybe high.
• A beefy server in AWS or GCP costs something like $1/hr, probably more for the really big ones. So in order to get to $20,000/run, we need 20,000 instance-hours. Let's ballpark a large training run at 1 day, so that's ~800 instances for one day. That feels within the realm of the numbers I've seen in papers.

Conclusion: Entirely plausible. Other conclusion: Lifetime cost of gasoline for a car is (in round numbers) the same as the cost of a new car. I hadn't realized they were so close. Other other conclusion: Now I understand why OpenAI needs billions o

nelhage

https://www.dropbox.com
https://drive.google.com
https://aws.amazon.com
https://cloud.google.com
https://hangouts.google.com/
https://www.salesforce.com
https://www.bitfinex.com
https://www.coinbase.com/
https://gemini.com/
https://bitbucket.org

nelhage

#include <stdio.h>
#include <math.h>
#include <stdint.h>

static float rt(float x) {
    volatile double g = static_cast<double>(x);
    return static_cast<float>(g);
}

int main() {

nelhage

#include <thread>
#include <experimental/optional>
#include <atomic>
#include <shared_mutex>
#include <mutex>
#include <iostream>
#include <vector>

using namespace std;

nelhage

This story is simplified from an attempt to write an AST walker for a toy compiler, but the essential facts are unchanged.

I am fairly new to Rust (but an experienced C++ programmer) and am trying to write a program to map an FnMut over a binary tree. I start with a simple tree definition, and try to write what seems to me to be the straightforward code:

use std::rc::Rc;

nelhage

Keybase proof

I hereby claim:

• I am nelhage on github.
• I am nelhage (https://keybase.io/nelhage) on keybase.
• I have a public key whose fingerprint is C808 7020 87F6 8CD8 C818 F239 DFC1 CF0D A816 9ACF

To claim this, I am signing this object:

nelhage

#include <memory>

using namespace std;

void accept_val(unique_ptr<int> i);
void accept_ref(unique_ptr<int> &i);
void accept_cref(const unique_ptr<int> &i);
void accept_rref(unique_ptr<int> &&i);

int main(int argc, char **argv) {