The Workflows
[experimental function](https://docs.cloud.google.com/workflows/docs/reference/stdlib/experimental.executions/map.md.txt),
`experimental.executions.map`, starts a workflow execution for each
corresponding argument, and waits for all of the executions to finish, returning
a list where each element is the result of an execution.

If you are using `experimental.executions.map` to support parallel work, you can
migrate your workflow to use parallel steps instead, executing ordinary
[`for` loops](https://docs.cloud.google.com/workflows/docs/reference/syntax/iteration.md.txt) in parallel.

A `parallel` step defines a part of your workflow where two or more steps can
execute concurrently. A `parallel` step waits until all the steps defined within
it have completed or are interrupted by an unhandled exception; execution then
continues. Like
`experimental.executions.map`, the execution order is not guaranteed. For
details, see the syntax reference page for
[parallel steps](https://docs.cloud.google.com/workflows/docs/reference/syntax/parallel-steps.md.txt).

Note that the use of `experimental.executions.map` or `workflows.executions.run`
requires additional [concurrent executions quota](https://docs.cloud.google.com/workflows/quotas.md.txt#quotas).
However, when using parallel steps with calls to connectors
inlined (see the [translation connector example](https://docs.cloud.google.com/workflows/docs/migrate-function-to-parallel.md.txt#inlined-workflow)), no
additional execution quota is required.

The following examples are intended to assist you when replacing the use of
`experimental.executions.map` with a `parallel` step.

## Translation workflow

Given a source and target language, the following workflow, named `translate`,
uses the
[Cloud Translation connector](https://docs.cloud.google.com/workflows/docs/reference/googleapis/translate/Overview.md.txt)
to translate some input text and return the result. Note that the Cloud Translation API
must be enabled.

### YAML

```yaml
  main:
    params: [args]
    steps:
    - basic_translate:
        call: googleapis.translate.v2.translations.translate
        args:
          body:
            q: ${args.text}
            target: ${args.target}
            format: "text"
            source: ${args.source}
        result: r
    - return_step:
        return: ${r}
```

### JSON

```json
  {
    "main": {
      "params": [
        "args"
      ],
      "steps": [
        {
          "basic_translate": {
            "call": "googleapis.translate.v2.translations.translate",
            "args": {
              "body": {
                "q": "${args.text}",
                "target": "${args.target}",
                "format": "text",
                "source": "${args.source}"
              }
            },
            "result": "r"
          }
        },
        {
          "return_step": {
            "return": "${r}"
          }
        }
      ]
    }
  }
```

Input for the preceding example:

```json
{
  "text": "Bonjour",
  "target": "en",
  "source": "fr"
}
```

The output should resemble the following:

```json
{
 "data": {
   "translations": [
     {
       "translatedText": "Hello"
     }
   ]
 }
}
```

## Batch translation workflow using `experimental.executions.map`

The following workflow translates a batch of texts. For each input,
`experimental.executions.map` executes the `translate` workflow created
previously.

### YAML

```yaml
  main:
     steps:
     - init:
         assign:
         - workflow_id: "translate"
         - texts_to_translate:
             - text: "hello world!"
               source: "en"
               target: "fr"
             - text: "你好 世界！"
               source: "zh-CN"
               target: "en"
             - text: "No hablo español!"
               source: "es"
               target: "en"
     - translate_texts:
         call: experimental.executions.map
         args:
             workflow_id: ${workflow_id}
             arguments: ${texts_to_translate}
         result: translated
     - return:
             return: ${translated}
```

### JSON

```json
  {
    "main": {
      "steps": [
        {
          "init": {
            "assign": [
              {
                "workflow_id": "translate"
              },
              {
                "texts_to_translate": [
                  {
                    "text": "hello world!",
                    "source": "en",
                    "target": "fr"
                  },
                  {
                    "text": "你好 世界！",
                    "source": "zh-CN",
                    "target": "en"
                  },
                  {
                    "text": "No hablo español!",
                    "source": "es",
                    "target": "en"
                  }
                ]
              }
            ]
          }
        },
        {
          "translate_texts": {
            "call": "experimental.executions.map",
            "args": {
              "workflow_id": "${workflow_id}",
              "arguments": "${texts_to_translate}"
            },
            "result": "translated"
          }
        },
        {
          "return": {
            "return": "${translated}"
          }
        }
      ]
    }
  }
```

The output should resemble the following:

```json
[
  {
    "data": {
      "translations": [
        {
          "translatedText": "Bonjour le monde!"
        }
      ]
    }
  },
  {
    "data": {
      "translations": [
        {
          "translatedText": "Hello world!"
        }
      ]
    }
  },
  {
    "data": {
      "translations": [
        {
          "translatedText": "I don't speak Spanish!"
        }
      ]
    }
  }
]
```

## Replace `experimental.executions.map` with a `for:in` loop

Instead of using the experimental function, you can use a parallel `for:in` loop
to translate the text. In the following example, the secondary workflow,
`translate`, can be used as is and the output should remain unchanged. You also
have the option of starting other secondary workflow executions in
[parallel branches](https://docs.cloud.google.com/workflows/docs/reference/syntax/parallel-steps.md.txt#parallel-branch).

A [shared variable](https://docs.cloud.google.com/workflows/docs/reference/syntax/parallel-steps.md.txt#variables),
`translated`, is used to store the results and is populated with empty strings
to enable static array indexing. If ordering is not required, you can use
[`list.concat`](https://docs.cloud.google.com/workflows/docs/reference/stdlib/list/concat.md.txt) to append the
results. All assignments in parallel steps are atomic.

### YAML

```yaml
main:
  params: []
  steps:
    - init:
        assign:
          - workflow_id: "translate"
          - texts_to_translate:
              - text: "hello world!"
                source: "en"
                target: "fr"
              - text: "你好 世界！"
                source: "zh-CN"
                target: "en"
              - text: "No hablo español!"
                source: "es"
                target: "en"
          - translated: ["", "", ""]  # to write to this variable, you must share it
    - parallel_translate:
        parallel:
          shared: [translated]
          for:
            in: ${texts_to_translate}
            index: i  # optional, use if index is required
            value: arg
            steps:
              - translate:
                  call: googleapis.workflowexecutions.v1.projects.locations.workflows.executions.run
                  args:
                    workflow_id: ${workflow_id}
                    argument: ${arg}
                  result: r
              - set_result:
                  assign:
                    - translated[i]: ${r}
    - return:
        return: ${translated}
```

### JSON

```json
{
  "main": {
    "params": [],
    "steps": [
      {
        "init": {
          "assign": [
            {
              "workflow_id": "translate"
            },
            {
              "texts_to_translate": [
                {
                  "text": "hello world!",
                  "source": "en",
                  "target": "fr"
                },
                {
                  "text": "你好 世界！",
                  "source": "zh-CN",
                  "target": "en"
                },
                {
                  "text": "No hablo español!",
                  "source": "es",
                  "target": "en"
                }
              ]
            },
            {
              "translated": [
                "",
                "",
                ""
              ]
            }
          ]
        }
      },
      {
        "parallel_translate": {
          "parallel": {
            "shared": [
              "translated"
            ],
            "for": {
              "in": "${texts_to_translate}",
              "index": "i",
              "value": "arg",
              "steps": [
                {
                  "translate": {
                    "call": "googleapis.workflowexecutions.v1.projects.locations.workflows.executions.run",
                    "args": {
                      "workflow_id": "${workflow_id}",
                      "argument": "${arg}"
                    },
                    "result": "r"
                  }
                },
                {
                  "set_result": {
                    "assign": [
                      {
                        "translated[i]": "${r}"
                      }
                    ]
                  }
                }
              ]
            }
          }
        }
      },
      {
        "return": {
          "return": "${translated}"
        }
      }
    ]
  }
}
```

## Replace `experimental.executions.map` with a `for:range` loop

Instead of using the experimental function, you can use a parallel `for:range`
loop to translate the text. By using a `for:range` loop, you can specify
the beginning and end of an iteration range. The output should remain unchanged.

### YAML

```yaml
main:
  params: []
  steps:
    - init:
        assign:
          - workflow_id: "translate"
          - texts_to_translate:
              - text: "hello world!"
                source: "en"
                target: "fr"
              - text: "你好 世界！"
                source: "zh-CN"
                target: "en"
              - text: "No hablo español!"
                source: "es"
                target: "en"
          - translated: ["", "", ""]  # to write to this variable, you must share it
    - parallel_translate:
        parallel:
          shared: [translated]
          for:
            range: ${[0, len(texts_to_translate) - 1]}
            value: i
            steps:
              - translate:
                  call: googleapis.workflowexecutions.v1.projects.locations.workflows.executions.run
                  args:
                    workflow_id: ${workflow_id}
                    argument: ${texts_to_translate[i]}
                  result: r
              - set_result:
                  assign:
                    - translated[i]: ${r}
    - return:
        return: ${translated}
```

### JSON

```json
{
  "main": {
    "params": [],
    "steps": [
      {
        "init": {
          "assign": [
            {
              "workflow_id": "translate"
            },
            {
              "texts_to_translate": [
                {
                  "text": "hello world!",
                  "source": "en",
                  "target": "fr"
                },
                {
                  "text": "你好 世界！",
                  "source": "zh-CN",
                  "target": "en"
                },
                {
                  "text": "No hablo español!",
                  "source": "es",
                  "target": "en"
                }
              ]
            },
            {
              "translated": [
                "",
                "",
                ""
              ]
            }
          ]
        }
      },
      {
        "parallel_translate": {
          "parallel": {
            "shared": [
              "translated"
            ],
            "for": {
              "range": "${[0, len(texts_to_translate) - 1]}",
              "value": "i",
              "steps": [
                {
                  "translate": {
                    "call": "googleapis.workflowexecutions.v1.projects.locations.workflows.executions.run",
                    "args": {
                      "workflow_id": "${workflow_id}",
                      "argument": "${texts_to_translate[i]}"
                    },
                    "result": "r"
                  }
                },
                {
                  "set_result": {
                    "assign": [
                      {
                        "translated[i]": "${r}"
                      }
                    ]
                  }
                }
              ]
            }
          }
        }
      },
      {
        "return": {
          "return": "${translated}"
        }
      }
    ]
  }
}
```

## Inline the workflow source code

If the secondary workflow is relatively brief, you might want to include it
directly within the main workflow for easier readability. For example, in the
following workflow, the source code for the `translate` workflow has been
inlined.

### YAML

```yaml
main:
  params: [args]
  steps:
    - init:
        assign:
          - workflow_id: "translate"
          - texts_to_translate:
              - text: "hello world!"
                source: "en"
                target: "fr"
              - text: "你好 世界！"
                source: "zh-CN"
                target: "en"
              - text: "No hablo español!"
                source: "es"
                target: "en"
          - translated: ["", "", ""]
    - parallel_translate:
        parallel:
          shared: [translated]  # to write to this variable, you must share it
          for:
            range: ${[0, len(texts_to_translate) - 1]}
            value: i
            steps:
              - basic_translate:
                  call: googleapis.translate.v2.translations.translate
                  args:
                    body:
                      q: ${args.text}
                      target: ${args.target}
                      format: "text"
                      source: ${args.source}
                  result: r
              - set_result:
                  assign:
                    - translated[i]: ${r}
    - return:
        return: ${translated}
```

### JSON

```json
{
  "main": {
    "params": [
      "args"
    ],
    "steps": [
      {
        "init": {
          "assign": [
            {
              "workflow_id": "translate"
            },
            {
              "texts_to_translate": [
                {
                  "text": "hello world!",
                  "source": "en",
                  "target": "fr"
                },
                {
                  "text": "你好 世界！",
                  "source": "zh-CN",
                  "target": "en"
                },
                {
                  "text": "No hablo español!",
                  "source": "es",
                  "target": "en"
                }
              ]
            },
            {
              "translated": [
                "",
                "",
                ""
              ]
            }
          ]
        }
      },
      {
        "parallel_translate": {
          "parallel": {
            "shared": [
              "translated"
            ],
            "for": {
              "range": "${[0, len(texts_to_translate) - 1]}",
              "value": "i",
              "steps": [
                {
                  "basic_translate": {
                    "call": "googleapis.translate.v2.translations.translate",
                    "args": {
                      "body": {
                        "q": "${args.text}",
                        "target": "${args.target}",
                        "format": "text",
                        "source": "${args.source}"
                      }
                    },
                    "result": "r"
                  }
                },
                {
                  "set_result": {
                    "assign": [
                      {
                        "translated[i]": "${r}"
                      }
                    ]
                  }
                }
              ]
            }
          }
        }
      },
      {
        "return": {
          "return": "${translated}"
        }
      }
    ]
  }
}
```

## What's next

- [Execute workflow steps in parallel](https://docs.cloud.google.com/workflows/docs/reference/syntax/parallel/execute-parallel-steps)
- [Quotas and limits for parallel steps](https://docs.cloud.google.com/workflows/quotas.md.txt#parallel_steps)