toSingle causes excessive stack traces #4594
Comments
|
Could you post a unit test that shows the problem. The stacktrace refers to a bunch of mappings which I guess is in |
|
Here is a unit test that demonstrates the situation: package com.example;
import junit.framework.Assert;
import org.junit.Test;
import rx.Observable;
import rx.Single;
import rx.functions.Action1;
import rx.subjects.PublishSubject;
public class ExampleUnitTest {
final int ITERATIONS = 10;
private Action1<Integer> assertStack(final int baseStack, final int additionalFrames, final int iterationFrames) {
return o -> Assert.assertEquals(baseStack + additionalFrames + ITERATIONS * iterationFrames, Thread.currentThread().getStackTrace().length);
}
@Test
public void testFlatMap() {
int baseStack = Thread.currentThread().getStackTrace().length;
PublishSubject<Integer> subject = PublishSubject.create();
Single<Integer> single1 = subject.toSingle().flatMap(integer -> {
Single<Integer> modified = Single.just(integer);
for (int i = 0; i < ITERATIONS; i++) {
modified = modified.map(n -> n + 1);
}
return modified;
});
Observable<Integer> observable = subject.concatMap(integer -> {
Observable<Integer> modified = Observable.just(integer);
for (int i = 0; i < ITERATIONS; i++) {
modified = modified.map(n -> n + 1);
}
return modified;
});
single1.subscribe(assertStack(baseStack, 34, 12));
observable.subscribe(assertStack(baseStack, 18, 5));
observable.toSingle().subscribe(assertStack(baseStack, 14, 0));
subject.onNext(0);
subject.onCompleted();
}
}The first subscription is my initial code. The third subscription is the comparison I was making. The second subscription makes clear that I was seeing such an improvement because the final |
|
We may be able to reduce the stack dept a bit but the problem is this: for (int i = 0; i < ITERATIONS; i++) {
modified = modified.map(n -> n + 1);
}Your composition gets unconventionally long this way and you might want to find another way of having that many maps chained (like collect them into
|
|
I edited my previous comment since the stack sizes were actually for |
|
I looked into the trampoline scheduler recently, and it looks like adding it into the chain with |
|
I see. The whole |
|
For the sake of completeness, here's a simpler (and perhaps more fair) test demonstrating the difference between package com.example;
import junit.framework.Assert;
import org.junit.Test;
import rx.Observable;
import rx.Single;
import rx.functions.Action1;
import rx.subjects.PublishSubject;
public class ExampleUnitTest {
final int ITERATIONS = 20;
private Action1<Integer> assertStack(final int baseStack, final int additionalFrames, final int iterationFrames) {
return o -> Assert.assertEquals(baseStack + additionalFrames + ITERATIONS * iterationFrames, Thread.currentThread().getStackTrace().length);
}
@Test
public void testFlatMap() {
int baseStack = Thread.currentThread().getStackTrace().length;
PublishSubject<Integer> subject = PublishSubject.create();
Single<Integer> single1 = subject.toSingle();
for (int i = 0; i < ITERATIONS; i++) {
single1 = single1.flatMap(integer -> Single.just(integer + 1));
}
Single<Integer> single2 = subject.toSingle();
for (int i = 0; i < ITERATIONS; i++) {
single2 = single2.toObservable().concatMap(integer -> Observable.just(integer + 1)).toSingle();
}
single1.subscribe(assertStack(baseStack, 10, 24));
single2.subscribe(assertStack(baseStack, 10, 8));
subject.onNext(0);
subject.onCompleted();
}
}It seems that using private Single.Transformer<Integer, Integer> transformer2(final Func1<Integer, Single<Integer>> mapper) {
return integerSingle -> integerSingle.toObservable().concatMap(it -> mapper.call(it).toObservable()).toSingle();
} |
|
Posted #4648. May not get all reduction but it's a base for further compaction. |
|
Thanks for looking into this. On Fri, Sep 30, 2016 at 2:40 PM, David Karnok [email protected]
|
|
Closing via #4648 |
I have the following code:
which produces the following stack trace:
When I change the code to:
The stack trace I get is:
This is happening on RxJava 1.1.9
The text was updated successfully, but these errors were encountered: