more | ||

pretty | ||

sample | ||

simple | ||

f.go | ||

go.mod | ||

makefile | ||

README.md |

# A minimalist calculator for fermi estimation

This project is a minimalist, calculator-style DSL for fermi estimation. It can multiply, divide, add and substract scalars, lognormals and beta distributions.

## Motivation

Sometimes, Squiggle, simple squiggle or squiggle.c are still too complicated and un-unix-like.

## Installation

```
make build
sudo make install
fermi
```

## Usage

```
$ fermi
5000000 12000000
=> 5.0M 12.0M
* beta 1 200
1.9K 123.1K
* 30 180
122.9K 11.7M
/ 48 52
2.5K 234.6K
/ 5 6
448.8 43.0K
/ 6 8
64.5 6.2K
/ 60
1.1 103.7
```

Perhaps this example is more understandable with comments and better units:

```
$ fermi
5M 12M # number of people living in Chicago
=> 5.0M 12.0M
* beta 1 200 # fraction of people that have a piano
1.9K 123.1K
30 180 # minutes it takes to tune a piano, including travel time
122.9K 11.7M
/ 48 52 # weeks a year pianotuners work for
2.5K 234.6K
/ 6 8 # hours a day
353.9 34.1K
/ 60 # minutes to an hour
5.9 568.3
=: piano_tuners_in_Chicago
piano_tuners_in_Chicago => 5.9 568.3
```

Here is instead an example using beta distributions and variables:

```
$ fermi
1 2
=> 1.0 2.0
* 1_000_000_000
=> 1000.0M 2.0B
=: x # assign to variable
x => 1000.0M 2.0B
. # clear the stack, i.e., make it be 1
beta 1 2
=> beta 1.0 2.0
beta 12 300
=> beta 13.0 302.0
=. y # assign to variable and clear the stack (return it to 1)
y => beta 13.0 302.0
x
=> 1000.0M 2.0B
* y
=> samples 31.3M 98.2M
```

The difference between `=: x`

and `=. y`

is that `=.`

clears the stack after the assignment.

If you type "help", you can see a small grammar:

```
$ fermi
help
Operation | Variable assignment | Special
Operation: operator operand
operator: (empty) | * | / | + | -
operand: scalar | lognormal | beta | variable
lognormal: low high
beta: beta alpha beta
Variable assignment: =: variable_name
Variable assignment and clear stack: =. variable_name
Special:
Clear stack: clear | c | .
Print this help message: help | h
Print debug info: debug | d
Exit: exit | e
Comment: # this is a comment
Examples:
+ 2
/ 2.5
* 1 10 (interpreted as lognormal)
+ 1 10
* beta 1 10
1 10 (multiplication taken as default operation)
=: x
.
1 100
+ x
# this is a comment
* 1 12 # this is an operation followed by a comment
exit
```

## Tips & tricks

- It's conceptually clearer to have all the multiplications first and then all the divisions
- For things between 0 and 1, consider using a beta distribution
- Because the model reads from standard input, you can pipe a model to it. For instance, try cat more/piano-tuners.f | fermi

## Different levels of complexity

The top level f.go file (400 lines) has a bunch of complexity: variables, parenthesis, samples, beta distributions. In the simple/ folder:

- f_simple.go (370 lines) strips variables and parenthesis, but keeps beta distributions, samples, and addition and substraction
- f_minimal.go (140 lines) strips everything that isn't lognormal and scalar multiplication and addition, plus a few debug options.

## Roadmap

Done:

- Write README
- Add division?
- Read from file?
- Save to file?
- Allow comments?
- Use a sed filter?
- Add proper comment processing

- Add show more info version
- Scalar multiplication and division
- Think how to integrate with squiggle.c to draw samples
- Copy the time to botec go code
- Define samplers
- Call those samplers when operating on distributions that can't be operted on algebraically

- Display output more nicely, with K/M/B/T
- Consider the following: make this into a stack-based DSL, with:
- Variables that can be saved to and then displayed
- Other types of distributions, particularly beta distributions? => But then this requires moving to bags of samples. It could still be ~instantaneous though.
- Added bags of samples to support addition and multiplication of betas and lognormals

- Figure out go syntax for
- Maps
- Joint types
- Enums

- Fix correlation problem, by spinning up a new randomness thing every time some serial computation is done.
- Clean up error code. Right now only needed for division
- Maintain
*both*a more complex thing that's more featureful*and*the more simple multiplication of lognormals thing. - Allow input with K/M/T

To (possibly) do:

- Specify number of samples as a command line option
- Document parenthesis syntax
- Add functions. Now easier to do with an explicit representation of the stakc
- Think about how to draw a histogram from samples
- Dump samples to file
- Represent samples/statistics in some other way
- Perhaps use qsort rather than full sorting
- Program into a small device, like a calculator?

Discarded:

~~Think of some way of calling bc~~