title: How to make RAY calculate multiple trials in parallel?
body: <p>My code is:</p>
  <pre><code>config = {
      &quot;num_workers&quot; : 19,
      #&quot;num_gpus&quot;: 1,
      &quot;gamma&quot; : tune.grid_search([0, 0.2, 0.4, 0.6, 0.8, 1]),       
      &quot;lr&quot; : tune.grid_search([1, 0.1, 0.01, 0.001, 0.0001, 0.00001, 0.000001])}
  </code></pre>
  <p>and:</p>
  <pre><code>analysis = tune.run(config=config)
  </code></pre>
  <p>When I run this, I have:</p>
  <pre><code>Number of trials: 23/42 (22 PENDING, 1 RUNNING)
  +----------------------------+----------+------------------------+---------+-------+--------+------------------+--------+----------+----------------------+----------------------+--------------------+
  | Trial name                 | status   | loc                    |   gamma |    lr |   iter |   total time (s) |     ts |   reward |   episode_reward_max |   episode_reward_min |   episode_len_mean |
  |----------------------------+----------+------------------------+---------+-------+--------+------------------+--------+----------+----------------------+----------------------+--------------------|
  | A2C_TradingEnv_b9572_00000 | RUNNING  | 192.168.252.130:361637 |     0   | 1     |     33 |          326.923 | 335920 |      nan |                  nan |                  nan |                nan |
  | A2C_TradingEnv_b9572_00001 | PENDING  |                        |     0.2 | 1     |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00002 | PENDING  |                        |     0.4 | 1     |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00003 | PENDING  |                        |     0.6 | 1     |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00004 | PENDING  |                        |     0.8 | 1     |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00005 | PENDING  |                        |     1   | 1     |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00006 | PENDING  |                        |     0   | 0.1   |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00007 | PENDING  |                        |     0.2 | 0.1   |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00008 | PENDING  |                        |     0.4 | 0.1   |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00009 | PENDING  |                        |     0.6 | 0.1   |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00010 | PENDING  |                        |     0.8 | 0.1   |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00011 | PENDING  |                        |     1   | 0.1   |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00012 | PENDING  |                        |     0   | 0.01  |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00013 | PENDING  |                        |     0.2 | 0.01  |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00014 | PENDING  |                        |     0.4 | 0.01  |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00015 | PENDING  |                        |     0.6 | 0.01  |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00016 | PENDING  |                        |     0.8 | 0.01  |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00017 | PENDING  |                        |     1   | 0.01  |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00018 | PENDING  |                        |     0   | 0.001 |        |                  |        |          |                      |                      |                    |
  | A2C_TradingEnv_b9572_00019 | PENDING  |                        |     0.2 | 0.001 |        |                  |        |          |                      |                      |                    |
  +----------------------------+----------+------------------------+---------+-------+--------+------------------+--------+----------+----------------------+----------------------+--------------------+
  ... 3 more trials not shown (3 PENDING)
  </code></pre>
  <p>So only one trial is running. I want to run multiple trials in parallel. When I want to run each trial on single CPU with:</p>
  <pre><code>analysis = tune.run(
      config=config,
      resources_per_trial = {&quot;cpu&quot;: 1, &quot;gpu&quot;: 0})
  </code></pre>
  <p>I have error:</p>
  <pre><code>Exception has occurred: ValueError
  Resources for &lt;class 'ray.rllib.agents.trainer_template.A2C'&gt; have been automatically set to &lt;ray.tune.utils.placement_groups.PlacementGroupFactory object at 0x7fe119c3f7c0&gt; by its `default_resource_request()` method. Please clear the `resources_per_trial` option.
  </code></pre>
  <p>What should I do to have multiple parallel trial runs with 1 CPU each?</p>