nrm2.h

/////////////////////////////////////////////////////////////////////
// = NMatrix
//
// A linear algebra library for scientific computation in Ruby.
// NMatrix is part of SciRuby.
//
// NMatrix was originally inspired by and derived from NArray, by
// Masahiro Tanaka: http://narray.rubyforge.org
//
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//
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// NMatrix is Copyright (c) 2012 - 2014, John Woods and the Ruby Science Foundation
//
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//
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// our Contributor Agreement:
//
// * https://github.com/SciRuby/sciruby/wiki/Contributor-Agreement
//
// == nrm2.h
//
// CBLAS nrm2 function
//

/*
 *             Automatically Tuned Linear Algebra Software v3.8.4
 *                    (C) Copyright 1999 R. Clint Whaley
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions, and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *   3. The name of the ATLAS group or the names of its contributers may
 *      not be used to endorse or promote products derived from this
 *      software without specific written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE ATLAS GROUP OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 */

#ifndef NRM2_H
# define NRM2_H

#include "math/long_dtype.h"


namespace nm { namespace math {

/*
 * Level 1 BLAS routine which returns the 2-norm of an n-vector x.
 #
 * Based on input types, these are the valid return types:
 *    int -> int
 *    float -> float or double
 *    double -> double
 *    complex64 -> float or double
 *    complex128 -> double
 */
template <typename ReturnDType, typename DType>
ReturnDType nrm2(const int N, const DType* X, const int incX) {
  const DType ONE = 1, ZERO = 0;
  typename LongDType<DType>::type scale = 0, ssq = 1, absxi, temp;


  if ((N < 1) || (incX < 1))    return ZERO;
  else if (N == 1)              return std::abs(X[0]);

  for (int i = 0; i < N; ++i) {
    absxi = std::abs(X[i*incX]);
    if (absxi != 0)
    {
      if (scale < absxi) {
        temp  = scale / absxi;
        scale = absxi;
        ssq   = ONE + ssq * (temp * temp);
      }
      else {
        temp = absxi / scale;
        ssq += temp * temp;
      }
    }
  }

  return scale * std::sqrt( ssq );
}


template <typename FloatDType>
static inline void nrm2_complex_helper(const FloatDType& xr, const FloatDType& xi, double& scale, double& ssq) {
  double absx = std::abs(xr);
  if (absx != 0)
  {
    if (scale < absx) {
      double temp  = scale / absx;
      scale = absx;
      ssq   = 1.0 + ssq * (temp * temp);
    }
    else {
      double temp = absx / scale;
      ssq += temp * temp;
    }
  }

  absx = std::abs(xi);
  if (absx != 0)
  {
    if (scale < absx) {
      double temp  = scale / absx;
      scale = absx;
      ssq   = 1.0 + ssq * (temp * temp);
    }
    else {
      double temp = absx / scale;
      ssq += temp * temp;
    }
  }
}

template <>
float nrm2(const int N, const Complex64* X, const int incX) {
  double scale = 0, ssq = 1;

  if ((N < 1) || (incX < 1))    return 0.0;

  for (int i = 0; i < N; ++i) {
    nrm2_complex_helper<float>(X[i*incX].r, X[i*incX].i, scale, ssq);
  }

  return scale * std::sqrt( ssq );
}

template <>
double nrm2(const int N, const Complex128* X, const int incX) {
  double scale = 0, ssq = 1;

  if ((N < 1) || (incX < 1))    return 0.0;

  for (int i = 0; i < N; ++i) {
    nrm2_complex_helper<double>(X[i*incX].r, X[i*incX].i, scale, ssq);
  }

  return scale * std::sqrt( ssq );
}

template <typename ReturnDType, typename DType>
inline void cblas_nrm2(const int N, const void* X, const int incX, void* result) {
  *reinterpret_cast<ReturnDType*>( result ) = nrm2<ReturnDType, DType>( N, reinterpret_cast<const DType*>(X), incX );
}



}} // end of namespace nm::math

#endif // NRM2_H

The difference

diff --git a/ext/nmatrix/math/nrm2.h b/ext/nmatrix/math/nrm2.h
index ac0c9ef..b7a31e6 100644
--- a/ext/nmatrix/math/nrm2.h
+++ b/ext/nmatrix/math/nrm2.h
@@ -85,14 +85,17 @@ ReturnDType nrm2(const int N, const DType* X, const int incX

   for (int i = 0; i < N; ++i) {
     absxi = std::abs(X[i*incX]);
-    if (scale < absxi) {
-      temp  = scale / absxi;
-      scale = absxi;
-      ssq   = ONE + ssq * (temp * temp);
-    }
-    else if(scale != 0) {
-      temp = absxi / scale;
-      ssq += temp * temp;
+    if (absxi != 0)
+    {
+      if (scale < absxi) {
+        temp  = scale / absxi;
+        scale = absxi;
+        ssq   = ONE + ssq * (temp * temp);
+      }
+      else {
+        temp = absxi / scale;
+        ssq += temp * temp;
+      }
     }
   }

@@ -103,25 +106,31 @@ ReturnDType nrm2(const int N, const DType* X, const int in
 template <typename FloatDType>
 static inline void nrm2_complex_helper(const FloatDType& xr, const FloatDType& 
   double absx = std::abs(xr);
-  if (scale < absx) {
-    double temp  = scale / absx;
-    scale = absx;
-    ssq   = 1.0 + ssq * (temp * temp);
-  }
-  else if(scale != 0)  {
-    double temp = absx / scale;
-    ssq += temp * temp;
+  if (absx != 0)
+  {
+    if (scale < absx) {
+      double temp  = scale / absx;
+      scale = absx;
+      ssq   = 1.0 + ssq * (temp * temp);
+    }
+    else {
+      double temp = absx / scale;
+      ssq += temp * temp;
+    }
   }

   absx = std::abs(xi);
-  if (scale < absx) {
-    double temp  = scale / absx;
-    scale = absx;
-    ssq   = 1.0 + ssq * (temp * temp);
-  }
-  else if(scale != 0)  {
-    double temp = absx / scale;
-    ssq += temp * temp;
+  if (absx != 0)
+  {
+    if (scale < absx) {
+      double temp  = scale / absx;
+      scale = absx;
+      ssq   = 1.0 + ssq * (temp * temp);
+    }
+    else {
+      double temp = absx / scale;
+      ssq += temp * temp;
+    }
   }
 }