tgravescs commented on code in PR #44690:
URL: https://github.com/apache/spark/pull/44690#discussion_r1475496985
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core/src/main/scala/org/apache/spark/resource/ResourceAllocator.scala:
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@@ -20,6 +20,49 @@ package org.apache.spark.resource
import scala.collection.mutable
import org.apache.spark.SparkException
+import org.apache.spark.resource.ResourceAmountUtils.ONE_ENTIRE_RESOURCE
+
+private[spark] object ResourceAmountUtils {
+ /**
+ * Using "double" to do the resource calculation may encounter a problem of
precision loss. Eg
+ *
+ * scala> val taskAmount = 1.0 / 9
+ * taskAmount: Double = 0.1111111111111111
+ *
+ * scala> var total = 1.0
+ * total: Double = 1.0
+ *
+ * scala> for (i <- 1 to 9 ) {
+ * | if (total >= taskAmount) {
+ * | total -= taskAmount
+ * | println(s"assign $taskAmount for task $i, total left: $total")
+ * | } else {
+ * | println(s"ERROR Can't assign $taskAmount for task $i, total
left: $total")
+ * | }
+ * | }
+ * assign 0.1111111111111111 for task 1, total left: 0.8888888888888888
+ * assign 0.1111111111111111 for task 2, total left: 0.7777777777777777
+ * assign 0.1111111111111111 for task 3, total left: 0.6666666666666665
+ * assign 0.1111111111111111 for task 4, total left: 0.5555555555555554
+ * assign 0.1111111111111111 for task 5, total left: 0.44444444444444425
+ * assign 0.1111111111111111 for task 6, total left: 0.33333333333333315
+ * assign 0.1111111111111111 for task 7, total left: 0.22222222222222204
+ * assign 0.1111111111111111 for task 8, total left: 0.11111111111111094
+ * ERROR Can't assign 0.1111111111111111 for task 9, total left:
0.11111111111111094
+ *
+ * So we multiply ONE_ENTIRE_RESOURCE to convert the double to long to avoid
this limitation.
+ * Double can display up to 16 decimal places, so we set the factor to
+ * 10, 000, 000, 000, 000, 000L.
+ */
+ final val ONE_ENTIRE_RESOURCE: Long = 10000000000000000L
Review Comment:
> I don't think this should touch so many parts of the code. Surely this
just affects how the resource request string is parsed and compared to
available resources
I believe the majority of the changes are still required here. This PR is
making it possible so that different tasks could use different resources per
task. The previous way we tracked addresses won't work because it statically
created an array of addressed based on a static configuration (ie all tasks get
the same resources per task). To properly support different tasks asking for
different resource the changes in this pr now pass around the value of what is
left. If I'm misunderstanding what you are saying please clarify.
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