github.com/livekit/protocol@v1.39.3/utils/parallel.go (about)

     1  // Copyright 2023 LiveKit, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package utils
    16  
    17  import (
    18  	"runtime"
    19  	"sync"
    20  
    21  	"go.uber.org/atomic"
    22  )
    23  
    24  // ParallelExec will executes the given function with each element of vals, if len(vals) >= parallelThreshold,
    25  // will execute them in parallel, with the given step size. So fn must be thread-safe.
    26  func ParallelExec[T any](vals []T, parallelThreshold, step uint64, fn func(T)) {
    27  	if uint64(len(vals)) < parallelThreshold {
    28  		for _, v := range vals {
    29  			fn(v)
    30  		}
    31  		return
    32  	}
    33  
    34  	// parallel - enables much more efficient multi-core utilization
    35  	start := atomic.NewUint64(0)
    36  	end := uint64(len(vals))
    37  
    38  	var wg sync.WaitGroup
    39  	numCPU := runtime.NumCPU()
    40  	if numCPU > len(vals) {
    41  		numCPU = len(vals)
    42  	}
    43  	wg.Add(numCPU)
    44  	for p := 0; p < numCPU; p++ {
    45  		go func() {
    46  			defer wg.Done()
    47  			for {
    48  				n := start.Add(step)
    49  				if n >= end+step {
    50  					return
    51  				}
    52  
    53  				for i := n - step; i < n && i < end; i++ {
    54  					fn(vals[i])
    55  				}
    56  			}
    57  		}()
    58  	}
    59  	wg.Wait()
    60  }