### Install ruby-prof

Source: https://ruby-prof.github.io/profiling-rails

Run the bundle command to install the newly added gem.

```bash
bundle install
```

--------------------------------

### Start Rails in profile environment

Source: https://ruby-prof.github.io/profiling-rails

Launch the Rails server or console using the profile environment.

```bash
bin/rails server -e profile
```

```bash
bin/rails console -e profile
```

--------------------------------

### Example code for call tree construction

Source: https://ruby-prof.github.io/architecture

A simple Ruby example demonstrating method calls that result in multiple call sites for the same method.

```ruby
def process
  validate
  save
end

def save
  validate
  write
end
```

--------------------------------

### Install ruby-prof gem

Source: https://ruby-prof.github.io/

Use this command to install the ruby-prof gem via RubyGems.

```bash
gem install ruby-prof
```

--------------------------------

### Generate ruby-prof example reports

Source: https://ruby-prof.github.io/reports

Executes the report generation script to profile a word-frequency workload.

```bash
ruby docs/public/examples/generate_reports.rb
```

--------------------------------

### Profile using Convenience API

Source: https://ruby-prof.github.io/getting-started

Use the RubyProf::Profile class to manually start and stop profiling, or use the block-based profile method.

```ruby
require 'ruby-prof'

profile = RubyProf::Profile.new

# profile the code
profile.start
# ... code to profile ...
result = profile.stop

# print a flat profile to text
printer = RubyProf::FlatPrinter.new(result)
printer.print(STDOUT)
```

```ruby
require 'ruby-prof'

# profile the code
result = RubyProf::Profile.profile do
  # ... code to profile ...
end

# print a graph profile to text
printer = RubyProf::GraphPrinter.new(result)
printer.print(STDOUT)
```

--------------------------------

### Configure profile environment

Source: https://ruby-prof.github.io/profiling-rails

Set up the profile environment by inheriting from production and adding the Rack::RubyProf middleware.

```ruby
# config/environments/profile.rb
require_relative "production"

Rails.application.configure do
  # Optional: reduce noise while profiling.
  config.log_level = :warn

  # Optional: disable controller/view caching if you want raw app execution timing.
  config.action_controller.perform_caching = false

  config.middleware.use Rack::RubyProf, path: Rails.root.join("tmp/profile")
end
```

--------------------------------

### Update printer options to keyword arguments

Source: https://ruby-prof.github.io/changelog

Demonstrates the transition from using an options hash to keyword arguments for printer methods.

```ruby
# Before:
printer.print(STDOUT, :min_percent => 2, :sort_method => :self_time)
# After:
printer.print(STDOUT, min_percent: 2, sort_method: :self_time)
```

--------------------------------

### Generate a GraphPrinter report

Source: https://ruby-prof.github.io/reports

Create a report by initializing a printer with a profile object and printing to an IO stream. The min_percent option filters methods based on their self-time contribution.

```ruby
profile = RubyProf::Profile.profile do
            ...
          end
printer = RubyProf::GraphPrinter.new(profile)
printer.print(STDOUT, min_percent: 2)
```

--------------------------------

### Configure Core API

Source: https://ruby-prof.github.io/getting-started

Initialize the RubyProf::Profile class directly to access advanced features like custom measurement modes.

```ruby
require 'ruby-prof'

profile = RubyProf::Profile.new(measure_mode: RubyProf::WALL_TIME)
result = profile.profile do
           ...
         end
```

--------------------------------

### Initialize a Profile object

Source: https://ruby-prof.github.io/architecture

Use the profile block to initiate a profiling run and capture method execution data.

```ruby
profile = RubyProf::Profile.profile do
  ...
end
```

--------------------------------

### Inspect generated reports

Source: https://ruby-prof.github.io/profiling-rails

List the files generated in the profile output directory.

```bash
ls -1 tmp/profile
```

--------------------------------

### Manage visit counters on method entry and exit

Source: https://ruby-prof.github.io/architecture

C-level logic for tracking method visits to detect recursion and manage stack state.

```c
// Method entry (prof_frame_push):
call_tree->visits++;
if (call_tree->method->visits > 0)
    call_tree->method->recursive = true;
call_tree->method->visits++;

// Method exit (prof_frame_pop):
call_tree->visits--;
call_tree->method->visits--;
```

--------------------------------

### Generate profile output

Source: https://ruby-prof.github.io/profiling-rails

Trigger a request to the server to generate the profiling reports.

```bash
curl http://127.0.0.1:3000/
```

--------------------------------

### Run ruby-prof via Command Line

Source: https://ruby-prof.github.io/getting-started

Execute profiling directly from the terminal without modifying source code.

```bash
ruby-prof [options] <script.rb> [--] [script-options]
```

```bash
ruby-prof -h
```

--------------------------------

### Set Measurement Mode via Environment Variable

Source: https://ruby-prof.github.io/advanced-usage

Configures the measurement mode using the RUBY_PROF_MEASURE_MODE environment variable.

```bash
export RUBY_PROF_MEASURE_MODE=wall
export RUBY_PROF_MEASURE_MODE=process
export RUBY_PROF_MEASURE_MODE=allocations
```

--------------------------------

### Enable Allocation Tracking

Source: https://ruby-prof.github.io/advanced-usage

Use the track_allocations option to enable detailed object allocation reporting.

```ruby
require 'ruby-prof'

RubyProf::Profile.profile(track_allocations: true) do
  ...
end
```

--------------------------------

### Generate a Flame Graph report

Source: https://ruby-prof.github.io/reports

Creates an HTML file containing a flame graph visualization of the profiling results.

```ruby
printer = RubyProf::FlameGraphPrinter.new(result)
printer.print(File.open("flame_graph.html", "w"))
```

--------------------------------

### Enable fiber merging in Rack middleware

Source: https://ruby-prof.github.io/advanced-usage

Configures the Rack adapter to merge fiber results automatically.

```ruby
config.middleware.use Rack::RubyProf, path: Rails.root.join("tmp/profile"), merge_fibers: true
```

--------------------------------

### Printer.print(io, options)

Source: https://ruby-prof.github.io/reports

Generates a report from a RubyProf::Profile object using a specific printer class. The printer is initialized with the profile and outputs to the provided IO object.

```APIDOC
## Printer.print(io, options)

### Description
Generates a profiling report based on the profile data provided during initialization. The output is written to the specified IO object, such as STDOUT or a file.

### Parameters
- **io** (IO) - Required - A writable IO object where the report will be written.
- **min_percent** (Float) - Optional - Minimum %self time for a method to be included (0–100). Default: 0.
- **max_percent** (Float) - Optional - Maximum %self time for a method to be included (0–100). Default: 100.
- **filter_by** (Symbol) - Optional - Which time metric to use when applying min_percent and max_percent. Default: :self_time.
- **sort_method** (Symbol) - Optional - How to sort methods. Values: :total_time, :self_time, :wait_time, :children_time.
- **max_depth** (Integer) - Optional - Maximum call tree depth to display. Applies to FlameGraphPrinter, CallStackPrinter, and CallInfoPrinter. Default: nil.

### Request Example
printer = RubyProf::GraphPrinter.new(profile)
printer.print(STDOUT, min_percent: 2)
```

--------------------------------

### Pause and Resume Profiling

Source: https://ruby-prof.github.io/changelog

Use RubyProf.resume with a block to automatically pause profiling after the block execution.

```ruby
10.times do |i| RubyProf.resume do # Some long process end end
result = RubyProf.stop
```

--------------------------------

### Graphviz DOT Profile Representation

Source: https://ruby-prof.github.io/public/examples/reports/graphviz_viewer.html

A DOT language representation of a ruby-prof call graph, defining nodes for methods and edges for call relationships with performance metrics.

```dot
digraph "Profile" {
rankdir=TB;
bgcolor="#FAFAFA";
node [fontname="Helvetica" fontsize=11 style="filled,rounded" shape=box fillcolor="#FFFFFF" color="#CCCCCC" penwidth=1.2];
edge [fontname="Helvetica" fontsize=9 color="#5B7DB1" arrowsize=0.7];
labelloc=t;
labeljust=l;
subgraph "Thread 464" {
624 [label="take\n(0%)"];
632 [label="-@\n(0%)"];
640 [label="each\n(0%)"];
640 -> 632 [label="25/25" penwidth=0.5];
648 [label="sort_by\n(0%)"];
648 -> 640 [label="1/1" penwidth=0.5];
656 [label="top_words\n(0%)"];
656 -> 648 [label="1/1" penwidth=0.5];
656 -> 624 [label="1/1" penwidth=0.5];
664 [label="[]=\n(13%)" fillcolor="#2E86C1" fontcolor="#FFFFFF"];
672 [label="+\n(9%)" fillcolor="#D4E6F1" fontcolor="#333333"];
680 [label="[]\n(11%)" fillcolor="#2E86C1" fontcolor="#FFFFFF"];
688 [label="each\n(72%)" fillcolor="#0D2483" fontcolor="#FFFFFF"];
688 -> 664 [label="5800/5800" penwidth=1.1];
688 -> 680 [label="5800/5800" penwidth=1.1];
688 -> 672 [label="5800/5800" penwidth=0.9];
696 [label="initialize\n(0%)"];
704 [label="count_words\n(72%)" fillcolor="#0D2483" fontcolor="#FFFFFF"];
704 -> 688 [label="1/1" penwidth=4.0];
704 -> 696 [label="1/1" penwidth=0.5];
712 [label="split\n(19%)" fillcolor="#2E86C1" fontcolor="#FFFFFF"];
720 [label="tokenize\n(19%)" fillcolor="#2E86C1" fontcolor="#FFFFFF"];
720 -> 712 [label="1/1" penwidth=1.5];
728 [label="gsub\n(8%)" fillcolor="#D4E6F1" fontcolor="#333333"];
736 [label="downcase\n(0%)"];
744 [label="normalize\n(8%)" fillcolor="#D4E6F1" fontcolor="#333333"];
744 -> 728 [label="1/1" penwidth=0.9];
744 -> 736 [label="1/1" penwidth=0.5];
752 [label="*\n(0%)"];
760 [label="run_example\n(100%)" fillcolor="#0D2483" fontcolor="#FFFFFF"];
760 -> 704 [label="1/1" penwidth=4.0];
760 -> 720 [label="1/1" penwidth=1.5];
760 -> 744 [label="1/1" penwidth=0.9];
760 -> 656 [label="1/1" penwidth=0.5];
760 -> 752 [label="1/1" penwidth=0.5];
768 [label="[global]\n(100%)" fillcolor="#0D2483" fontcolor="#FFFFFF"];
768 -> 760 [label="1/1" penwidth=4.0];
}
subgraph cluster_776 {
label = "[global]";
fontname = "Helvetica";
fontcolor = "#1A35A6";
fontsize = 14;
color = "#1A35A6";
style = "rounded,dashed";
penwidth = 1.5;
768;
}
subgraph cluster_784 {
label = "Object";
fontname = "Helvetica";
```

--------------------------------

### Pause and Resume Profiling

Source: https://ruby-prof.github.io/getting-started

Control profiling execution flow by pausing and resuming during runtime.

```ruby
require 'ruby-prof'

profile = RubyProf::Profile.new

# profile the code
profile.start
# ... code to profile ...

profile.pause
# ... other code ...

profile.resume
# ... code to profile ...

result = profile.stop
```

```ruby
require 'ruby-prof'

profile = RubyProf::Profile.new

# profile the code
profile.start
# ... code to profile ...

profile.pause
# ... other code ...

profile.resume do
  # ... code to profile...
end

result = profile.stop
```

--------------------------------

### Merge threads and fibers in ruby-prof

Source: https://ruby-prof.github.io/advanced-usage

Collapses results for threads and fibers sharing the same root method into a single entry.

```ruby
profile = RubyProf::Profile.profile do
            ...
          end
profile.merge!
```

--------------------------------

### Persist profile results using Marshal

Source: https://ruby-prof.github.io/advanced-usage

Saves and loads profiling data using Ruby's Marshal library. Ensure data sources are trusted to prevent arbitrary code execution.

```ruby
profile_1 = RubyProf::Profile.profile do
  ...
end

# Save the results
data = Marshal.dump(profile_1)

# Sometime later load the results
profile_2 = Marshal.load(data)
```

--------------------------------

### Set Measurement Mode in Ruby

Source: https://ruby-prof.github.io/advanced-usage

Configures the measurement mode during the initialization of a RubyProf::Profile object.

```ruby
profile = RubyProf::Profile.new(measure_mode: RubyProf::WALL_TIME)
profile = RubyProf::Profile.new(measure_mode: RubyProf::PROCESS_TIME)
profile = RubyProf::Profile.new(measure_mode: RubyProf::ALLOCATIONS)
```

--------------------------------

### Enable Profiling in Test::Unit

Source: https://ruby-prof.github.io/changelog

Include the RubyProf::Test module in a test class to enable profiling for that test suite.

```ruby
include RubyProf::Test
```

--------------------------------

### Lookup or create child CallTree node

Source: https://ruby-prof.github.io/architecture

Checks the parent's children hash table for an existing CallTree node; creates a new one if it does not exist.

```c
call_tree = call_tree_table_lookup(parent_call_tree->children, method->key);

if (!call_tree)
{
    call_tree = prof_call_tree_create(method, parent_call_tree, ...);
    prof_call_tree_add_child(parent_call_tree, call_tree);
}
```

--------------------------------

### Generate multiple reports simultaneously

Source: https://ruby-prof.github.io/reports

Uses the MultiPrinter to output several report formats in a single profiling run to a specified directory.

```ruby
printer = RubyProf::MultiPrinter.new(result)
printer.print(path: ".", profile: "profile")
```

--------------------------------

### Accumulate total time at outermost visit

Source: https://ruby-prof.github.io/architecture

C-level logic to prevent double-counting of time by only accumulating measurements when the visit count is 1.

```c
// Only accumulate total_time at the outermost visit
if (call_tree->visits == 1)
    call_tree->measurement->total_time += total_time;

if (call_tree->method->visits == 1)
    call_tree->method->measurement->total_time += total_time;
```

--------------------------------

### RubyProf Printer Classes

Source: https://ruby-prof.github.io/reports

Overview of the available printer classes used to generate reports from profiling results.

```APIDOC
## RubyProf Printer Classes

### Description
RubyProf provides several printer classes to output profiling results in different formats. Each printer is initialized with a `result` object and provides a `print` method.

### Available Printers
- **RubyProf::FlatPrinter**: Generates a flat report showing overall time per method.
- **RubyProf::GraphPrinter**: Generates a text-based graph report showing call relationships.
- **RubyProf::GraphHtmlPrinter**: Generates an HTML-based graph report with hyperlinks.
- **RubyProf::FlameGraphPrinter**: Generates an interactive HTML flame graph visualization.
- **RubyProf::CallStackPrinter**: Generates an HTML visualization of execution paths.
- **RubyProf::DotPrinter**: Generates output for Graphviz visualization.
- **RubyProf::CallTreePrinter**: Generates output in the calltree format for KCachegrind.
- **RubyProf::CallInfoPrinter**: Generates a call tree report with timing information for debugging.
- **RubyProf::MultiPrinter**: Generates multiple report types in a single run.

### Usage Example
```ruby
printer = RubyProf::FlameGraphPrinter.new(result)
printer.print(File.open("flame_graph.html", "w"))
```
```

--------------------------------

### Define a recursive method for call tree analysis

Source: https://ruby-prof.github.io/architecture

A simple recursive Ruby method used to demonstrate how new CallTree nodes are generated at each recursion level.

```ruby
def simple(n)
  sleep(1)
  return if n == 0
  simple(n - 1)
end

simple(2)
```

--------------------------------

### Add ruby-prof to Gemfile

Source: https://ruby-prof.github.io/profiling-rails

Include the ruby-prof gem within a specific profile group in your Gemfile.

```ruby
group :profile do
  gem 'ruby-prof'
end
```

--------------------------------

### Exclude Common Methods

Source: https://ruby-prof.github.io/advanced-usage

Use a predefined set of common methods to exclude from profiling results.

```ruby
profile.exclude_common_methods!
```

--------------------------------

### Retrieve parent CallTree node

Source: https://ruby-prof.github.io/architecture

Retrieves the parent CallTree node from the current stack frame during a method call event.

```c
parent_call_tree = frame->call_tree;
```

--------------------------------

### Exclude Methods from Profiling

Source: https://ruby-prof.github.io/advanced-usage

Remove specific methods from the call graph to reduce noise and focus on relevant performance data.

```ruby
profile = RubyProf::Profile.new(...)
profile.exclude_methods!(Integer, :times, ...)
profile.start
```

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