From 7e28fb88186dfe5e92accdc855f679f1c4eb582d Mon Sep 17 00:00:00 2001
From: Ondrej Mirtes <ondrej@mirtes.cz>
Date: Sun, 16 Feb 2020 14:33:54 +0100
Subject: [PATCH] Scheduler - configurable minimum number of jobs per process

---
 conf/config.neon                         |  5 ++++-
 src/Parallel/Scheduler.php               | 12 ++++++++++--
 tests/PHPStan/Parallel/SchedulerTest.php | 17 ++++++++++++++++-
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/conf/config.neon b/conf/config.neon
index 30aaa9df46..5c789651b1 100644
--- a/conf/config.neon
+++ b/conf/config.neon
@@ -42,6 +42,7 @@ parameters:
 		jobSize: 20
 		processTimeout: 60.0
 		maximumNumberOfProcesses: 32
+		minimumNumberOfJobsPerProcess: 2
 	polluteScopeWithLoopInitialAssignments: true
 	polluteScopeWithAlwaysIterableForeach: true
 	polluteCatchScopeWithTryAssignments: false
@@ -152,7 +153,8 @@ parametersSchema:
 	parallel: structure([
 		jobSize: int(),
 		processTimeout: float(),
-		maximumNumberOfProcesses: int()
+		maximumNumberOfProcesses: int(),
+		minimumNumberOfJobsPerProcess: int()
 	])
 	polluteScopeWithLoopInitialAssignments: bool()
 	polluteScopeWithAlwaysIterableForeach: bool()
@@ -388,6 +390,7 @@ services:
 		arguments:
 			jobSize: %parallel.jobSize%
 			maximumNumberOfProcesses: %parallel.maximumNumberOfProcesses%
+			minimumNumberOfJobsPerProcess: %parallel.minimumNumberOfJobsPerProcess%
 
 	-
 		class: PHPStan\Parser\CachedParser
diff --git a/src/Parallel/Scheduler.php b/src/Parallel/Scheduler.php
index 8b6ebbc33c..541e1bc5a6 100644
--- a/src/Parallel/Scheduler.php
+++ b/src/Parallel/Scheduler.php
@@ -11,13 +11,18 @@ class Scheduler
 	/** @var int */
 	private $maximumNumberOfProcesses;
 
+	/** @var int */
+	private $minimumNumberOfJobsPerProcess;
+
 	public function __construct(
 		int $jobSize,
-		int $maximumNumberOfProcesses
+		int $maximumNumberOfProcesses,
+		int $minimumNumberOfJobsPerProcess
 	)
 	{
 		$this->jobSize = $jobSize;
 		$this->maximumNumberOfProcesses = $maximumNumberOfProcesses;
+		$this->minimumNumberOfJobsPerProcess = $minimumNumberOfJobsPerProcess;
 	}
 
 	/**
@@ -31,7 +36,10 @@ public function scheduleWork(
 	): Schedule
 	{
 		$jobs = array_chunk($files, $this->jobSize);
-		$numberOfProcesses = min(count($jobs), $cpuCores);
+		$numberOfProcesses = min(
+			(int) floor(count($jobs) / $this->minimumNumberOfJobsPerProcess),
+			$cpuCores
+		);
 
 		return new Schedule(min($numberOfProcesses, $this->maximumNumberOfProcesses), $jobs);
 	}
diff --git a/tests/PHPStan/Parallel/SchedulerTest.php b/tests/PHPStan/Parallel/SchedulerTest.php
index 1eae9ff939..adf59fcf4e 100644
--- a/tests/PHPStan/Parallel/SchedulerTest.php
+++ b/tests/PHPStan/Parallel/SchedulerTest.php
@@ -13,6 +13,7 @@ public function dataSchedule(): array
 			[
 				1,
 				16,
+				1,
 				50,
 				115,
 				1,
@@ -21,6 +22,7 @@ public function dataSchedule(): array
 			[
 				16,
 				16,
+				1,
 				30,
 				124,
 				5,
@@ -29,6 +31,7 @@ public function dataSchedule(): array
 			[
 				16,
 				3,
+				1,
 				30,
 				124,
 				3,
@@ -37,11 +40,21 @@ public function dataSchedule(): array
 			[
 				16,
 				16,
+				1,
 				10,
 				298,
 				16,
 				[10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 8],
 			],
+			[
+				16,
+				16,
+				2,
+				30,
+				124,
+				2,
+				[30, 30, 30, 30, 4],
+			],
 		];
 	}
 
@@ -49,6 +62,7 @@ public function dataSchedule(): array
 	 * @dataProvider dataSchedule
 	 * @param int $cpuCores
 	 * @param int $maximumNumberOfProcesses
+	 * @param int $minimumNumberOfJobsPerProcess
 	 * @param int $jobSize
 	 * @param int $numberOfFiles
 	 * @param int $expectedNumberOfProcesses
@@ -57,6 +71,7 @@ public function dataSchedule(): array
 	public function testSchedule(
 		int $cpuCores,
 		int $maximumNumberOfProcesses,
+		int $minimumNumberOfJobsPerProcess,
 		int $jobSize,
 		int $numberOfFiles,
 		int $expectedNumberOfProcesses,
@@ -64,7 +79,7 @@ public function testSchedule(
 	): void
 	{
 		$files = array_fill(0, $numberOfFiles, 'file.php');
-		$scheduler = new Scheduler($jobSize, $maximumNumberOfProcesses);
+		$scheduler = new Scheduler($jobSize, $maximumNumberOfProcesses, $minimumNumberOfJobsPerProcess);
 		$schedule = $scheduler->scheduleWork($cpuCores, $files);
 
 		$this->assertSame($expectedNumberOfProcesses, $schedule->getNumberOfProcesses());