Sparklyr中set.seed功能当前是否正常可用？2017年10月曾存问题

Hey there! Let me clear up the confusion around set.seed() in sparklyr, especially since you ran into issues back in 2017.

First off: the seed functionality works reliably in modern sparklyr versions—the early pain points you might have faced are mostly resolved. Here's what you need to know to use it correctly now:

Key Differences from Base R #

Back in 2017, a major frustration was that base R's set.seed() only affected your local R session, not the distributed Spark cluster. That meant random operations (like sampling, training random forests, or splitting data) wouldn't produce reproducible results, even if you set a seed locally.

Now, sparklyr provides a dedicated function to handle distributed randomness:

• Use spark_set_seed(sc, your_seed_value) where sc is your Spark connection object. This propagates the seed across all nodes in the cluster, ensuring consistent randomness for Spark operations.

Example Workflow #

Here's a quick, actionable example to show how it works:

library(sparklyr)

# Connect to your Spark cluster
sc <- spark_connect(master = "local")

# Set the distributed seed for Spark operations
spark_set_seed(sc, 1234)

# Now any random Spark task will be reproducible
iris_tbl <- copy_to(sc, iris)
sampled_iris <- iris_tbl %>% sample_frac(0.5)

# Clean up the connection
spark_disconnect(sc)

Important Notes #

• Stick to spark_set_seed(): Base R's set.seed() still won't control Spark's distributed randomness—reserve that for local R tasks only.
• Version check: Make sure you're running a recent sparklyr version (ideally 1.5 or newer). Older versions might still have edge cases, but modern releases have solid seed support.
• Minor edge cases: In rare scenarios with complex distributed operations, you might see tiny inconsistencies, but for most common use cases (model training, sampling, data splitting), results will be fully reproducible.

To sum it up: The seed-related headaches from 2017 are fixed. As long as you use spark_set_seed() with your Spark connection, you can reliably control randomness in sparklyr now.

内容的提问来源于stack exchange，提问作者Bob Wakefield