diff --git a/include/gwmodelpp/GWRBasic.h b/include/gwmodelpp/GWRBasic.h
index d9217eb1..50daa284 100644
--- a/include/gwmodelpp/GWRBasic.h
+++ b/include/gwmodelpp/GWRBasic.h
@@ -687,7 +687,7 @@ class GWRBasic : public GWRBase, public IBandwidthSelectable, public IVarialbeSe
 public:     // Implement IGwmParallelOpenmpEnabled
     void setOmpThreadNum(const int threadNum) override { mOmpThreadNum = threadNum; }
     void setGPUId(const int gpuId) override { mGpuId = gpuId; };
-    void setGroupSize(const double size) override { mGroupLength = size; };
+    void setGroupSize(const size_t size) override { mGroupLength = size; };
 
 protected:
 
diff --git a/include/gwmodelpp/GWRMultiscale.h b/include/gwmodelpp/GWRMultiscale.h
index 88acc42c..6bec0067 100644
--- a/include/gwmodelpp/GWRMultiscale.h
+++ b/include/gwmodelpp/GWRMultiscale.h
@@ -625,7 +625,7 @@ class GWRMultiscale : public SpatialMultiscaleAlgorithm, public IBandwidthSelect
 
 public:     // IParallelCudaEnabled interface
     void setGPUId(const int gpuId) override { mGpuId = gpuId; }
-    void setGroupSize(const double size) override { mGroupLength = size; }
+    void setGroupSize(const size_t size) override { mGroupLength = size; }
 
 protected:
 
diff --git a/include/gwmodelpp/IParallelizable.h b/include/gwmodelpp/IParallelizable.h
index 182850e3..ec5a4fff 100644
--- a/include/gwmodelpp/IParallelizable.h
+++ b/include/gwmodelpp/IParallelizable.h
@@ -137,7 +137,7 @@ struct IParallelCudaEnabled
      * 对于大多数 GPU 可选择值 64。
      * 
      */
-    virtual void setGroupSize(const double size) = 0;
+    virtual void setGroupSize(const size_t size) = 0;
     
 };