add: RrefixSum.*lengthToHost

Author: IgorErin

src/GraphBLAS-sharp.Backend/Predefined/PrefixSum.fs

@@ -38,3 +38,25 @@ module internal PrefixSum =
         fun (processor: MailboxProcessor<_>) allocationMode (inputArray: ClArray<int>) (totalSum: ClCell<int>) ->
 
             scan processor allocationMode inputArray totalSum 0
+
+    let standardExcludeInplaceLengthToHost clContext workGroupSize =
+
+        let scan = standardExcludeInplace clContext workGroupSize
+
+        let resultLength = Array.zeroCreate<int> 1
+
+        fun (processor: MailboxProcessor<_>) (positions: ClArray<int>) ->
+
+            let resultLengthGpu = clContext.CreateClCell 0
+
+            let _, r =
+                scan processor positions resultLengthGpu
+
+            let res =
+                processor.PostAndReply(fun ch -> Msg.CreateToHostMsg<_>(r, resultLength, ch))
+
+            processor.Post(Msg.CreateFreeMsg<_>(r))
+
+            res.[0]
+
+

src/GraphBLAS-sharp.Backend/Vector/DenseVector/DenseVector.fs

@@ -95,30 +95,17 @@ module DenseVector =
         let getBitmap = ClArray.map clContext workGroupSize <| Map.option 1 0
 
         let prefixSum =
-            PrefixSum.standardExcludeInplace clContext workGroupSize
+            PrefixSum.standardExcludeInplaceLengthToHost clContext workGroupSize
 
         let allIndices = ClArray.init clContext workGroupSize <@ id @>
 
         let allValues = ClArray.map clContext workGroupSize Map.optionToValueOrZero
 
-        let resultLength = Array.zeroCreate<int> 1
-
         fun (processor: MailboxProcessor<_>) allocationMode (vector: ClArray<'a option>) ->
 
             let positions = getBitmap processor DeviceOnly vector
 
-            let resultLengthGpu = clContext.CreateClCell 0
-
-            let _, r =
-                prefixSum processor positions resultLengthGpu
-
-            let resultLength =
-                let res =
-                    processor.PostAndReply(fun ch -> Msg.CreateToHostMsg<_>(r, resultLength, ch))
-
-                processor.Post(Msg.CreateFreeMsg<_>(r))
-
-                res.[0]
+            let resultLength = prefixSum processor positions
 
             // compute result indices
             let resultIndices =
@@ -131,11 +118,11 @@ module DenseVector =
             processor.Post <| Msg.CreateFreeMsg<_>(allIndices)
 
             // compute result values
-            let allValues = allValues processor DeviceOnly vector
-
             let resultValues =
                 clContext.CreateClArrayWithSpecificAllocationMode<'a>(allocationMode, resultLength)
 
+            let allValues = allValues processor DeviceOnly vector
+
             scatterValues processor positions allValues resultValues
 
             processor.Post <| Msg.CreateFreeMsg<_>(allValues)