diff --git a/blas/double.cpp b/blas/double.cpp
new file mode 100644
index 0000000..8fd0709
--- /dev/null
+++ b/blas/double.cpp
@@ -0,0 +1,33 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2009 Gael Guennebaud <gael.guennebaud@inria.fr>
+// Copyright (C) 2012 Chen-Pang He <jdh8@ms63.hinet.net>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#define SCALAR        double
+#define SCALAR_SUFFIX d
+#define SCALAR_SUFFIX_UP "D"
+#define ISCOMPLEX     0
+
+#include "level1_impl.h"
+#include "level1_real_impl.h"
+#include "level2_impl.h"
+#include "level2_real_impl.h"
+#include "level3_impl.h"
+
+double BLASFUNC(dsdot)(int* n, float* x, int* incx, float* y, int* incy)
+{
+  if(*n<=0) return 0;
+
+  if(*incx==1 && *incy==1)    return (vector(x,*n).cast<double>().cwiseProduct(vector(y,*n).cast<double>())).sum();
+  else if(*incx>0 && *incy>0) return (vector(x,*n,*incx).cast<double>().cwiseProduct(vector(y,*n,*incy).cast<double>())).sum();
+  else if(*incx<0 && *incy>0) return (vector(x,*n,-*incx).reverse().cast<double>().cwiseProduct(vector(y,*n,*incy).cast<double>())).sum();
+  else if(*incx>0 && *incy<0) return (vector(x,*n,*incx).cast<double>().cwiseProduct(vector(y,*n,-*incy).reverse().cast<double>())).sum();
+  else if(*incx<0 && *incy<0) return (vector(x,*n,-*incx).reverse().cast<double>().cwiseProduct(vector(y,*n,-*incy).reverse().cast<double>())).sum();
+  else return 0;
+}
+