Start Softmax section of Support Primitives doc

* Written as a test bed for typesetting math content

* Need to decide how much detail to go into

docs/source/Supported_Primitives_Guide.rst

+==========================
+Supported Primitives Guide
+==========================
+
+------------
+Introduction
+------------
+
+This document contains details of supported primitives in Composable Kernel (CK). In contrast to the API Reference
+Guide, the Supported Primitives Guide is an introduction to the math which underpins the algorithms implemented in CK.
+
+Softmax
+^^^^^^^
+
+For vectors :math:`x^{(1)}, x^{(2)}, \ldots, x^{(T)}` of size :math:`B` we can decompose the softmax of concatenated
+:math:`x = [ x^{(1)}\ | \ \ldots \ | \ x^{(T)} ]` as,
+
+.. math::
+   :nowrap:
+
+   \begin{align}
+      m(x) & = m( [ x^{(1)}\ | \ \ldots \ | \ x^{(T)} ] ) = \max( m(x^{(1)}),\ldots, m(x^{(T)}) )  \\
+      f(x) & = [\exp( m(x^{(1)}) - m(x) ) f( x^{(1)} )\ | \ \ldots \ | \ \exp( m(x^{(T)}) - m(x) ) f( x^{(T)} )] \\
+      l(x) & = \exp( m(x^{(1)}) - m(x) )\ l(x^{(1)}) + \ldots + \exp( m(x^{(T)}) - m(x) )\ l(x^{(1)}) \\
+      \operatorname{softmax}(x) &= f(x)\ / \ l(x)
+   \end{align}
+
+where :math:`f(x^{(j)}) = \exp( x^{(j)} - m(x^{(j)}) )` is of size :math:`B` and
+:math:`l(x^{(j)}) = f(x_1^{(j)})+ \ldots+ f(x_B^{(j)})` is a scalar.
\ No newline at end of file

docs/source/index.rst

@@ -7,4 +7,8 @@ Composable Kernel User Guide
    :caption: Contents:
    :numbered:
 
-   Linux_Install_Guide
+   Linux_Install_Guide
\ No newline at end of file
+   Supported_Primitives_Guide
+   API_Reference_Guide
+   Contributors_Guide
+   Disclaimer
\ No newline at end of file