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+---
+title : "API Documentation"
+author_profile: false
+excerpt: "Data parallel API"
+header:
+  overlay_color: "#5DADE2"
+permalink: /docs/API/introduction.html
+sidebar:
+  nav : docs
+---
+
+
+Data parallel array indices are divided into two types. 
+
+* Internal indices, such as complex, colour, spin degrees of freedom 
+* spatial (space-time) indices.
+
+The ranges of all internal degrees are determined by template parameters, 
+and known at compile time. The ranges of spatial indices are dynamic, run time
+values and the Cartesian structure information is contained and accessed via `Grid` objects.
+
+Grid objects are the controlling entity for the decomposition of a distributed `Lattice`
+array across MPI tasks, nodes, SIMD lanes, accelerators. Threaded loops are used
+as appropriate on host code.
+
+Data parallel operations can only be performed between Lattice objects constructed
+from the same Grid pointer. These are called `conformable` operations.
+
+We will focus initially on the internal indices as these are the building blocks assembled
+in Lattice container classes. Every Lattice container class constructor requires a Grid object 
+pointer. 
+