@grnsft/if/src/if-run/builtins/multiply/README.md

Impact Framework

# Multiply

`multiply` is a generic plugin for multiplying two or more values in an `input` array.

You provide the names of the values you want to multiply, and a name to use to append the product to the output array.

For example, you could multiply `cpu/energy` and `network/energy` and name the result `energy-product`. `energy-product` would then be added to every observation in your input array as the product of `cpu/energy` and `network/energy`.

## Parameters

### Plugin config

Two parameters are required in config: `input-parameters` and `output-parameter`.

`input-parameters`: an array of strings. Each string should match an existing key in the `inputs` array
`output-parameter`: a string defining the name to use to add the product of the input parameters to the output array.

### Plugin parameter metadata

The `parameter-metadata` section contains information about `description`, `unit` and `aggregation-method` of the parameters of the inputs and outputs

- `inputs`: describe parameters of the `input-parameters` of the config. Each parameter has:

  - `description`: description of the parameter
  - `unit`: unit of the parameter
  - `aggregation-method`: aggregation method object of the parameter
    - `time`: this value is used for `horizontal` aggregation. It can be of the following values: `sum`, `avg`, `copy`, or `none`.
    - `component`: this value is used for `vertical` aggregation. It can be of the following values: `sum`, `avg`, `copy`, or `none`.

- `outputs`: describe the parameter of the `output-parameter` of the config. The parameter has the following attributes:
  - `description`: description of the parameter
  - `unit`: unit of the parameter
  - `aggregation-method`: aggregation method object of the parameter
    - `time`: this value is used for `horizontal` aggregation. It can be of the following values: `sum`, `avg`, `copy`, or `none`.
    - `component`: this value is used for `vertical` aggregation. It can be of the following values: `sum`, `avg`, `copy`, or `none`.

### Mapping

The `mapping` block is an optional block. It is added in the plugin section and allows the plugin to receive a parameter from the input with a different name than the one the plugin uses for data manipulation. The parameter with the mapped name will not appear in the outputs. It also maps the output parameter of the plugin. The structure of the `mapping` block is:

```yaml
multiply:
  method: Multiply
  path: 'builtin'
  mapping:
    'parameter-name-in-the-plugin': 'parameter-name-in-the-input'
```

### Inputs

All of `input-parameters` must be available in the input array.

## Returns

- `output-parameter`: the product of all `input-parameters` with the parameter name defined by `output-parameter` in config.

## Calculation

```pseudocode
output = input0 * input1 * input2 ... inputN
```

## Implementation

To run the plugin, you must first create an instance of `Multiply`. Then, you can call `execute()`.

```typescript
import {Multiply} from 'builtins';

const config = {
  inputParameters: ['cpu/energy', 'network/energy'],
  outputParameter: 'energy-product',
};

const parametersMetadata = {inputs: {}, outputs: {}};
const mapping = {};
const multiply = Multiply(config, parametersMetadata, mapping);
const result = await multiply.execute([
  {
    duration: 3600,
    timestamp: '2021-01-01T00:00:00Z',
    'cpu/energy': 0.001,
    'memory/energy': 0.0005,
  },
]);
```

## Example manifest

IF users will typically call the plugin as part of a pipeline defined in a manifest file. In this case, instantiating the plugin is handled by `if-run` and does not have to be done explicitly by the user. The following is an example manifest that calls `multiply`:

```yaml
name: multiply-demo
description:
tags:
initialize:
  plugins:
    multiply:
      method: Multiply
      path: 'builtin'
      config:
        input-parameters: ['cpu/energy', 'network/energy']
        output-parameter: 'energy-product'
tree:
  children:
    child:
      pipeline:
        compute:
          - multiply
      inputs:
        - timestamp: 2023-08-06T00:00
          duration: 3600
          cpu/energy: 0.001
          network/energy: 0.001
```

You can run this example by saving it as `./examples/manifests/test/multiply.yml` and executing the following command from the project root:

```sh
npm i -g @grnsft/if
if-run --manifest ./examples/manifests/test/multiply.yml --output ./examples/outputs/multiply.yml
```

The results will be saved to a new `yaml` file in `./examples/outputs`

## Errors

`Multiply` uses one of the IF error classes.

### `MissingInputDataError`

This error arises when a necessary piece of input data is missing from the `inputs` array.
Every element in the `inputs` array must contain:

- `timestamp`
- `duration`
- whatever values you passed to `input-parameters`

For more information on our error classes, please visit [our docs](https://if.greensoftware.foundation/reference/errors