fix: int64 indexing migration batch 6 - loop counters and index types

- Default.All.cs: int i -> long i for size iteration
- Default.Any.cs: int i -> long i for size iteration
- StackedMemoryPool.cs: int i -> long i (count param is long)
- np.random.poisson.cs: int i -> long i for size iteration
- np.random.bernoulli.cs: int i -> long i for size iteration
- np.random.randn.cs: int i -> long i for size iteration
- NDArray.Indexing.Masking.cs:
  - int idx -> long idx for trueCount iteration
  - GetInt32 -> GetInt64 (nonzero returns NDArray<long>[])
  - int valueIdx -> long valueIdx for mask.size iteration

All changes follow INT64_DEVELOPER_GUIDE.md patterns.

Author: Nucs

docs/INT64_MIGRATION_PROGRESS.md

@@ -18,6 +18,62 @@ This document tracks the progress of migrating recent commits to comply with the
 
 ---
 
+## Completed Fixes (Session 4)
+
+### 32. Default.All.cs - Loop counter fix
+
+**Location**: `src/NumSharp.Core/Backends/Default/Logic/Default.All.cs`
+
+**Changes**:
+- `var len = nd.size; for (int i = 0; i < len; i++)` → `long len = nd.size; for (long i = 0; i < len; i++)`
+
+### 33. Default.Any.cs - Loop counter fix
+
+**Location**: `src/NumSharp.Core/Backends/Default/Logic/Default.Any.cs`
+
+**Changes**:
+- Same fix as Default.All.cs
+
+### 34. np.random.poisson.cs - Loop counter fix
+
+**Location**: `src/NumSharp.Core/RandomSampling/np.random.poisson.cs`
+
+**Changes**:
+- `var len = result.size; for (int i = 0; i < len; i++)` → `long len; for (long i ...)`
+
+### 35. np.random.bernoulli.cs - Loop counter fix
+
+**Location**: `src/NumSharp.Core/RandomSampling/np.random.bernoulli.cs`
+
+**Changes**:
+- Same pattern fix for loop counter
+
+### 36. StackedMemoryPool.cs - Loop counter fix
+
+**Location**: `src/NumSharp.Core/Backends/Unmanaged/Pooling/StackedMemoryPool.cs`
+
+**Changes**:
+- `for (int i = 0; i < count; i++, addr += SingleSize)` → `for (long i = 0; i < count; i++, ...)`
+- `count` parameter is `long`, so loop counter must be `long`
+
+### 37. NDArray.Indexing.Masking.cs - Multiple fixes
+
+**Location**: `src/NumSharp.Core/Selection/NDArray.Indexing.Masking.cs`
+
+**Changes**:
+- `for (int idx = 0; idx < trueCount; idx++)` → `for (long idx = 0; idx < trueCount; idx++)`
+- `indices[dim].GetInt32(idx)` → `indices[dim].GetInt64(idx)` (nonzero now returns `NDArray<long>[]`)
+- `int valueIdx = 0; for (int i = 0; i < mask.size; i++)` → `long valueIdx = 0; for (long i ...)`
+
+### 38. np.random.randn.cs - Loop counter fix
+
+**Location**: `src/NumSharp.Core/RandomSampling/np.random.randn.cs`
+
+**Changes**:
+- `for (int i = 0; i < array.size; i++)` → `for (long i = 0; i < array.size; i++)`
+
+---
+
 ## Completed Fixes (Session 3)
 
 ### 30. np.random.shuffle.cs - NextLong fix

src/NumSharp.Core/Backends/Default/Logic/Default.All.cs

@@ -54,8 +54,8 @@ private static unsafe bool AllImpl<T>(NDArray nd) where T : unmanaged
 
                 // Scalar fallback for contiguous arrays
                 var addr = (T*)nd.Address;
-                var len = nd.size;
-                for (int i = 0; i < len; i++)
+                long len = nd.size;
+                for (long i = 0; i < len; i++)
                 {
                     if (addr[i].Equals(default(T)))
                         return false;

src/NumSharp.Core/Backends/Default/Logic/Default.Any.cs

@@ -54,8 +54,8 @@ private static unsafe bool AnyImpl<T>(NDArray nd) where T : unmanaged
 
                 // Scalar fallback for contiguous arrays
                 var addr = (T*)nd.Address;
-                var len = nd.size;
-                for (int i = 0; i < len; i++)
+                long len = nd.size;
+                for (long i = 0; i < len; i++)
                 {
                     if (!addr[i].Equals(default(T)))
                         return true;

src/NumSharp.Core/Backends/Unmanaged/Pooling/StackedMemoryPool.cs

@@ -204,7 +204,7 @@ public unsafe void AllocateCount(long count)
                 var block = new UnmanagedMemoryBlock<byte>(blocksize);
 
                 var addr = new IntPtr(block.Address);
-                for (int i = 0; i < count; i++, addr += SingleSize)
+                for (long i = 0; i < count; i++, addr += SingleSize)
                     availables_blocks.Push(addr);
 
                 _blocks.Add(block);

src/NumSharp.Core/RandomSampling/np.random.bernoulli.cs

@@ -42,9 +42,9 @@ public NDArray bernoulli(double p, params int[] size)
             unsafe
             {
                 var addr = result.Address;
-                var len = result.size;
+                long len = result.size;
                 Func<double> nextDouble = randomizer.NextDouble;
-                for (int i = 0; i < len; i++)
+                for (long i = 0; i < len; i++)
                     addr[i] = nextDouble() < p ? 1 : 0;
             }
 

src/NumSharp.Core/RandomSampling/np.random.poisson.cs

@@ -38,9 +38,9 @@ public NDArray poisson(double lam, params int[] size)
             var result = new NDArray<double>(size);
             unsafe
             {
-                var len = result.size;
+                long len = result.size;
                 var resultArray = result.Address;
-                for (int i = 0; i < len; i++)
+                for (long i = 0; i < len; i++)
                     resultArray[i] = Knuth(lam);
             }
 

src/NumSharp.Core/RandomSampling/np.random.randn.cs

@@ -89,7 +89,7 @@ public NDArray normal(double loc, double scale, params int[] size)
                 var dst = array.Address;
 
                 Func<double> nextDouble = randomizer.NextDouble;
-                for (int i = 0; i < array.size; i++)
+                for (long i = 0; i < array.size; i++)
                     dst[i] = loc + scale * Math.Sqrt(-2.0 * Math.Log(1.0 - nextDouble()))
                                         * Math.Sin(2.0 * Math.PI * (1.0 - nextDouble()));
 

src/NumSharp.Core/Selection/NDArray.Indexing.Masking.cs

@@ -175,13 +175,13 @@ private NDArray BooleanMaskPartialShape(NDArray<bool> mask)
             var result = new NDArray(this.dtype, new Shape(resultShape));
 
             // Copy selected slices using the nonzero indices
-            for (int idx = 0; idx < trueCount; idx++)
+            for (long idx = 0; idx < trueCount; idx++)
             {
                 // Build the index tuple from nonzero results
                 var srcSlice = this;
                 for (int dim = 0; dim < mask.ndim; dim++)
                 {
-                    srcSlice = srcSlice[indices[dim].GetInt32(idx)];
+                    srcSlice = srcSlice[indices[dim].GetInt64(idx)];
                 }
                 np.copyto(result[idx], srcSlice);
             }
@@ -284,8 +284,8 @@ private void SetBooleanMaskAxis0(NDArray<bool> mask, NDArray value)
             // NumSharp represents scalars as shape [1], not shape []
             bool isScalarValue = value.size == 1;
 
-            int valueIdx = 0;
-            for (int i = 0; i < mask.size; i++)
+            long valueIdx = 0;
+            for (long i = 0; i < mask.size; i++)
             {
                 if (mask.GetBoolean(i))
                 {