It raises JavaScript heap out of memory when many trials(>300) are executed

[Sundrops]

Short summary about the issue/question:
Just like the title says
Brief what process you are following:

-----------------------------------------------------------------------
                Experiment start time 2020-02-25 12:36:51
-----------------------------------------------------------------------
(node:150893) ExperimentalWarning: The fs.promises API is experimental
FATAL ERROR: MarkCompactCollector: semi-space copy, fallback in old gen Allocation failed - JavaScript heap out of memory
 1: 0x8daaa0 node::Abort() [node]
 2: 0x8daaec  [node]
 3: 0xad73ce v8::Utils::ReportOOMFailure(v8::internal::Isolate*, char const*, bool) [node]
 4: 0xad7604 v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, bool) [node]
 5: 0xec4c32  [node]
 6: 0xeebdf1 v8::internal::EvacuateNewSpaceVisitor::Visit(v8::internal::HeapObject*, int) [node]
 7: 0xeefe37 void v8::internal::LiveObjectVisitor::VisitBlackObjectsNoFail<v8::internal::EvacuateNewSpaceVisitor, v8::internal::MajorNonAtomicMarkingState>(v8::internal::MemoryChunk*, v8::internal::MajorNon
AtomicMarkingState*, v8::internal::EvacuateNewSpaceVisitor*, v8::internal::LiveObjectVisitor::IterationMode) [node]
 8: 0xef8af2 v8::internal::FullEvacuator::RawEvacuatePage(v8::internal::Page*, long*) [node]
 9: 0xee7cb1 v8::internal::Evacuator::EvacuatePage(v8::internal::Page*) [node]
10: 0xee7fb2 v8::internal::PageEvacuationTask::RunInParallel() [node]
11: 0xee045f v8::internal::ItemParallelJob::Task::RunInternal() [node]
12: 0xee0f97 v8::internal::ItemParallelJob::Run(std::shared_ptr<v8::internal::Counters>) [node]
13: 0xeec76e void v8::internal::MarkCompactCollectorBase::CreateAndExecuteEvacuationTasks<v8::internal::FullEvacuator, v8::internal::MarkCompactCollector>(v8::internal::MarkCompactCollector*, v8::internal::
ItemParallelJob*, v8::internal::RecordMigratedSlotVisitor*, v8::internal::MigrationObserver*, long) [node]
14: 0xef79fd v8::internal::MarkCompactCollector::EvacuatePagesInParallel() [node]
15: 0xef7b66 v8::internal::MarkCompactCollector::Evacuate() [node]
16: 0xef8602 v8::internal::MarkCompactCollector::CollectGarbage() [node]
17: 0xed0451 v8::internal::Heap::MarkCompact() [node]
18: 0xed0b41 v8::internal::Heap::PerformGarbageCollection(v8::internal::GarbageCollector, v8::GCCallbackFlags) [node]
19: 0xed1744 v8::internal::Heap::CollectGarbage(v8::internal::AllocationSpace, v8::internal::GarbageCollectionReason, v8::GCCallbackFlags) [node]
20: 0xed43b1 v8::internal::Heap::AllocateRawWithRetryOrFail(int, v8::internal::AllocationSpace, v8::internal::AllocationAlignment) [node]
21: 0xe9c695  [node]
22: 0xea3f0a v8::internal::Factory::NewRawOneByteString(int, v8::internal::PretenureFlag) [node]

How to reproduce it:

nni Environment:

• nni version: 1.3
• nni mode(local|pai|remote): local
• OS: unbuntu
• python version: 3.7
• is conda or virtualenv used?: conda
• is running in docker?: no