OutOfMemoryException F# snippets (dotnet#7818)

Author: albert-du

snippets/fsharp/System/OutOfMemoryException/Overview/data1.fs

@@ -0,0 +1,38 @@
+module data1
+
+// <Snippet3>
+open System
+
+let getData () =
+    let rnd = Random()
+    [|  for i = 1 to 200000000 do
+            rnd.NextDouble()
+            if i % 10000000 = 0 then
+                printfn $"Retrieved {i:N0} items of data." |]
+    
+let getMean values =
+    let sum = Array.sum values
+
+    sum / float values.Length
+
+let values = getData ()
+// Compute mean.
+printfn $"Sample mean: {getMean values}, N = {values.Length}"
+
+// The example displays output like the following:
+//    Retrieved 10,000,000 items of data.
+//    Retrieved 20,000,000 items of data.
+//    Retrieved 30,000,000 items of data.
+//    Retrieved 40,000,000 items of data.
+//    Retrieved 50,000,000 items of data.
+//    Retrieved 60,000,000 items of data.
+//    Retrieved 70,000,000 items of data.
+//    Retrieved 80,000,000 items of data.
+//    Retrieved 90,000,000 items of data.
+//    Retrieved 100,000,000 items of data.
+//    Retrieved 110,000,000 items of data.
+//    Retrieved 120,000,000 items of data.
+//    Retrieved 130,000,000 items of data.
+//
+//    Unhandled Exception: OutOfMemoryException.
+// </Snippet3>

snippets/fsharp/System/OutOfMemoryException/Overview/data2.fs

@@ -0,0 +1,31 @@
+module data2
+
+// <Snippet4>
+open System
+// open System.IO
+
+let getResult () =
+    let chunkSize = 50000000
+    let nToGet = 200000000
+    let rnd = Random()
+    // use fs = new FileStream(@".\data.bin", FileMode.Create)
+    // use bin = new BinaryWriter(fs)
+    // bin.Write 0
+    let mutable n = 0
+    let mutable sum = 0.
+    for _ = 0 to int (ceil (nToGet / chunkSize |> float) - 1.) do
+        for _ = 0 to min (nToGet - n - 1) (chunkSize - 1) do
+            let value = rnd.NextDouble()
+            sum <- sum + value
+            n <- n + 1
+            // bin.Write(value)
+    // bin.Seek(0, SeekOrigin.Begin) |> ignore
+    // bin.Write n
+    sum / float n, n
+
+let mean, n = getResult ()
+printfn $"Sample mean: {mean}, N = {n:N0}"
+
+// The example displays output like the following:
+//    Sample mean: 0.500022771458399, N = 200,000,000
+// </Snippet4>

snippets/fsharp/System/OutOfMemoryException/Overview/failfast1.fs

@@ -0,0 +1,24 @@
+module failfast1
+
+// <Snippet2>
+open System
+
+try
+    // Outer block to handle any unexpected exceptions.
+    try
+        let s = "This"
+        let s = s.Insert(2, "is ")
+
+        // Throw an OutOfMemoryException exception.
+        raise (OutOfMemoryException())
+    with
+    | :? ArgumentException ->
+        printfn "ArgumentException in String.Insert"
+
+    // Execute program logic.
+with :? OutOfMemoryException as e ->
+    printfn "Terminating application unexpectedly..."
+    Environment.FailFast $"Out of Memory: {e.Message}"
+// The example displays the following output:
+//        Terminating application unexpectedly...
+// </Snippet2>

snippets/fsharp/System/OutOfMemoryException/Overview/fs.fsproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="failfast1.fs" />
+    <Compile Include="sb_example1.fs" />
+    <Compile Include="data1.fs" />
+    <Compile Include="data2.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/OutOfMemoryException/Overview/sb_example1.fs

@@ -0,0 +1,17 @@
+module sb_example1
+
+// <Snippet1>
+open System
+open System.Text
+
+let sb = StringBuilder(15, 15)
+sb.Append "Substring #1 "
+|> ignore
+try
+    sb.Insert(0, "Substring #2 ", 1)
+    |> ignore
+with :? OutOfMemoryException as e ->
+    printfn $"Out of Memory: {e.Message}"
+// The example displays the following output:
+//    Out of Memory: Insufficient memory to continue the execution of the program.
+// </Snippet1>

xml/System/OutOfMemoryException.xml

@@ -80,6 +80,7 @@ An <xref:System.OutOfMemoryException> exception has two major causes:
      This type of <xref:System.OutOfMemoryException> exception represents a catastrophic failure. If you choose to handle the exception, you should include a `catch` block that calls the <xref:System.Environment.FailFast%2A?displayProperty=nameWithType> method to terminate your app and add an entry to the system event log, as the following example does.  
   
      :::code language="csharp" source="~/snippets/csharp/System/OutOfMemoryException/Overview/failfast1.cs" id="Snippet2":::
+     :::code language="fsharp" source="~/snippets/fsharp/System/OutOfMemoryException/Overview/failfast1.fs" id="Snippet2":::
      :::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.outofmemoryexception/vb/failfast1.vb" id="Snippet2":::  
   
  Some of the conditions under which the exception is thrown and the actions you can take to eliminate it include the following:  
@@ -89,6 +90,7 @@ An <xref:System.OutOfMemoryException> exception has two major causes:
 You are attempting to increase the length of a <xref:System.Text.StringBuilder> object beyond the size specified by its <xref:System.Text.StringBuilder.MaxCapacity%2A?displayProperty=nameWithType> property. The following example illustrates the <xref:System.OutOfMemoryException> exception thrown by a call to the <xref:System.Text.StringBuilder.Insert%28System.Int32%2CSystem.String%2CSystem.Int32%29?displayProperty=nameWithType> method when the example tries to insert a string that would cause the object's <xref:System.Text.StringBuilder.Length%2A> property to exceed its maximum capacity.  
   
 :::code language="csharp" source="~/snippets/csharp/System/OutOfMemoryException/Overview/sb_example1.cs" interactive="try-dotnet" id="Snippet1":::
+:::code language="fsharp" source="~/snippets/fsharp/System/OutOfMemoryException/Overview/sb_example1.fs" id="Snippet1":::
 :::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.outofmemoryexception/vb/sb_example1.vb" id="Snippet1":::
 
 You can do either of the following to address the error:  
@@ -128,11 +130,13 @@ To prevent the <xref:System.OutOfMemoryException> exceptions, you must modify yo
 The following example gets a array that consists of 200 million floating-point values and then calculates their mean. The output from the example shows that, because the example stores the entire array in memory before it calculates the mean, an <xref:System.OutOfMemoryException> is thrown.  
 
 :::code language="csharp" source="~/snippets/csharp/System/OutOfMemoryException/Overview/data1.cs" id="Snippet3":::
+:::code language="fsharp" source="~/snippets/fsharp/System/OutOfMemoryException/Overview/data1.fs" id="Snippet3":::
 :::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.outofmemoryexception/vb/data1.vb" id="Snippet3":::  
   
 The following example eliminates the <xref:System.OutOfMemoryException> exception by processing the incoming data without storing the entire data set in memory, serializing the data to a file if necessary to permit further processing (these lines are commented out in the example, since in this case they produce a file whose size is greater than 1GB), and returning the calculated mean and the number of cases to the calling routine.  
 
 :::code language="csharp" source="~/snippets/csharp/System/OutOfMemoryException/Overview/data2.cs" id="Snippet4":::
+:::code language="fsharp" source="~/snippets/fsharp/System/OutOfMemoryException/Overview/data2.fs" id="Snippet4":::
 :::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.outofmemoryexception/vb/data2.vb" id="Snippet4":::  
   
 **You are repeatedly concatenating large strings.**