parallel.foreach

问题 Parallel.For(0, Height, new ParallelOptions { MaxDegreeOfParallelism = 6 }, y => { int currentLine = y * BMPData.Stride; for (int x = 0; x < Width; x = x + BPX) { var b = pixels[currentLine + x]; var g = pixels[currentLine + x + 1]; var r = pixels[currentLine + x + 2]; int avg = (r + g + b) / 3; pixels[currentLine + x] = (byte)avg; pixels[currentLine + x + 1] = (byte)avg; pixels[currentLine + x + 2] = (byte)avg; } }); This is basically a parallel code where it turns bitmap data pixels into

问题 I have 2 loops(nested), trying to do a simple parallelisation pseudocode : for item1 in data1 (~100 million row) for item2 in data2 (~100 rows) result = process(item1,item2) // couple of if conditions hashset.add(result) // while adding, incase of a duplicate i also decide wihch one to retain process(item1,item2) to be precise has 4 if conditions bases on values in item1 and item2.(time taken is less than 50ms) data1 size is Nx17 data2 size is Nx17 result size is 1x17 (result is joined into a

问题 So I am attempting to process records from a datatable one row at a time. I am new to multi-threaded environments and I was asked to use Parallel.Foreach Loop. I wanted to know how local variables are treated in a Parallel execution mode. Following is my code. Parallel.ForEach(dtReportData.Tables[0].AsEnumerable(), drow => { string strType = drow["type"]; //Based on this type, I am executing logic from a switch case. }); Now. I want to know if I can declare and assign value to the variable

问题 I have a section of C# code as follows. This code summarizes a column of 'doubles' in a DataTable : var data = this.Db.ExecuteRead(query, this.Score.Name); var time = 0.0; foreach (DataRow row in data.Rows) { time += this.ParseDouble(row[0].ToString()) / MillisecondsPerMinute; } This code takes 4 seconds to execute. I wanted to speed it up, so I parallelized it as follows: Parallel.ForEach( data.AsEnumerable(), row => { time += this.ParseDouble(row[0].ToString()) / MillisecondsPerMinute; });

问题 I have a section of C# code as follows. This code summarizes a column of 'doubles' in a DataTable : var data = this.Db.ExecuteRead(query, this.Score.Name); var time = 0.0; foreach (DataRow row in data.Rows) { time += this.ParseDouble(row[0].ToString()) / MillisecondsPerMinute; } This code takes 4 seconds to execute. I wanted to speed it up, so I parallelized it as follows: Parallel.ForEach( data.AsEnumerable(), row => { time += this.ParseDouble(row[0].ToString()) / MillisecondsPerMinute; });

问题 I am using the Renci SSH.NET package version 2016. I am downloading files from an external server. I usually can download about one file every 6 seconds which is bad when you have thousands of files. I recently tried to change the foreach loops to Parallel.ForEach . Doing that changed the files downloaded times to 1.5 seconds. Except when I checked the files they all had 0 KB's so it did not download anything. Is there anything wrong with the parallel loop? I am new to C# and trying to

问题 I am using the Renci SSH.NET package version 2016. I am downloading files from an external server. I usually can download about one file every 6 seconds which is bad when you have thousands of files. I recently tried to change the foreach loops to Parallel.ForEach . Doing that changed the files downloaded times to 1.5 seconds. Except when I checked the files they all had 0 KB's so it did not download anything. Is there anything wrong with the parallel loop? I am new to C# and trying to

问题 I have two databases. The first one has about 70k rows with 3 columns. the second one has 790k rows with 2 columns. Both databases have a common variable grantee_name . I want to match each row of the first database to one or more rows of the second database based on this grantee_name . Note that merge will not work because the grantee_name do not match perfectly. There are different spellings etc. So, I am using the fuzzyjoin package and trying the following: library("haven"); library(

问题 I have two databases. The first one has about 70k rows with 3 columns. the second one has 790k rows with 2 columns. Both databases have a common variable grantee_name . I want to match each row of the first database to one or more rows of the second database based on this grantee_name . Note that merge will not work because the grantee_name do not match perfectly. There are different spellings etc. So, I am using the fuzzyjoin package and trying the following: library("haven"); library(

来源： https://stackoverflow.com/questions/51748047/how-often-does-parallel-for-invoke-localinit