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| <title>The GNU Fortran Compiler: DOT_PRODUCT</title> |
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| <a name="DOT_005fPRODUCT-_002d_002d_002d-Dot-product-function"></a> |
| <h3 class="section">8.66 <code>DOT_PRODUCT</code> — Dot product function</h3> |
| <a name="index-DOT_005fPRODUCT"></a> |
| <a name="index-dot-product"></a> |
| <a name="index-vector-product"></a> |
| <a name="index-product_002c-vector"></a> |
| |
| <dl compact="compact"> |
| <dt><em>Description</em>:</dt> |
| <dd><p><code>DOT_PRODUCT(VECTOR_A, VECTOR_B)</code> computes the dot product multiplication |
| of two vectors <var>VECTOR_A</var> and <var>VECTOR_B</var>. The two vectors may be |
| either numeric or logical and must be arrays of rank one and of equal size. If |
| the vectors are <code>INTEGER</code> or <code>REAL</code>, the result is |
| <code>SUM(VECTOR_A*VECTOR_B)</code>. If the vectors are <code>COMPLEX</code>, the result |
| is <code>SUM(CONJG(VECTOR_A)*VECTOR_B)</code>. If the vectors are <code>LOGICAL</code>, |
| the result is <code>ANY(VECTOR_A .AND. VECTOR_B)</code>. |
| </p> |
| </dd> |
| <dt><em>Standard</em>:</dt> |
| <dd><p>Fortran 95 and later |
| </p> |
| </dd> |
| <dt><em>Class</em>:</dt> |
| <dd><p>Transformational function |
| </p> |
| </dd> |
| <dt><em>Syntax</em>:</dt> |
| <dd><p><code>RESULT = DOT_PRODUCT(VECTOR_A, VECTOR_B)</code> |
| </p> |
| </dd> |
| <dt><em>Arguments</em>:</dt> |
| <dd><table> |
| <tr><td width="15%"><var>VECTOR_A</var></td><td width="70%">The type shall be numeric or <code>LOGICAL</code>, rank 1.</td></tr> |
| <tr><td width="15%"><var>VECTOR_B</var></td><td width="70%">The type shall be numeric if <var>VECTOR_A</var> is of numeric type or <code>LOGICAL</code> if <var>VECTOR_A</var> is of type <code>LOGICAL</code>. <var>VECTOR_B</var> shall be a rank-one array.</td></tr> |
| </table> |
| |
| </dd> |
| <dt><em>Return value</em>:</dt> |
| <dd><p>If the arguments are numeric, the return value is a scalar of numeric type, |
| <code>INTEGER</code>, <code>REAL</code>, or <code>COMPLEX</code>. If the arguments are |
| <code>LOGICAL</code>, the return value is <code>.TRUE.</code> or <code>.FALSE.</code>. |
| </p> |
| </dd> |
| <dt><em>Example</em>:</dt> |
| <dd><div class="smallexample"> |
| <pre class="smallexample">program test_dot_prod |
| integer, dimension(3) :: a, b |
| a = (/ 1, 2, 3 /) |
| b = (/ 4, 5, 6 /) |
| print '(3i3)', a |
| print * |
| print '(3i3)', b |
| print * |
| print *, dot_product(a,b) |
| end program test_dot_prod |
| </pre></div> |
| </dd> |
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