[Docs] Move environment variables to separate page (#341)

docs/api/env_variables.rst

@@ -0,0 +1,58 @@
+.. meta::
+  :description: rocSHMEM environment variables reference
+  :keywords: rocSHMEM, ROCm, API, environment variables, environment, reference
+
+********************************************************************
+rocSHMEM environment variables
+********************************************************************
+
+This section describes the important environment variables used to
+control the behavior of rocSHMEM.
+
+.. list-table::
+    :header-rows: 1
+    :widths: 35,14,51
+
+    * - **Environment variable**
+      - **Default value**
+      - **Value**
+
+    * - | ``ROCSHMEM_HEAP_SIZE``
+        | Defines the size of the rocSHMEM symmetric heap in bytes.
+      - ``1073741824`` (1 GB)
+      - | Size in bytes.
+        | Note the heap is on the GPU memory.
+
+    * - | ``ROCSHMEM_MAX_NUM_CONTEXTS``
+        | Defines the number of contexts an application can use.
+      - ``32``
+      - Maximum number of contexts.
+
+    * - | ``ROCSHMEM_MAX_NUM_TEAMS``
+        | Defines the number of teams an application can use.
+      - ``40``
+      - Maximum number of teams.
+
+    * - | ``ROCSHMEM_UNIQUEID_WITH_MPI``
+        | Defines whether rocSHMEM is expected to use MPI when using the uniqueId based initialization.
+      - ``0``
+      - | 0: Do not use MPI.
+        | 1: Use MPI.
+
+    * - | ``ROCSHMEM_DISABLE_MIXED_IPC``
+        | Defines whether to force using the network conduit even when IPC is available.
+      - ``0``
+      - | 0: Use IPC when available.
+        | 1: Force network conduit.
+
+    * - | ``ROCSHMEM_GDA_ALTERNATE_QP_PORTS``
+        | Enables/Disables having QPs alternate their mappings across rocSHMEM contexts.
+      - ``1``
+      - | 0: Disabled.
+        | 1: Enabled (helps saturate bandwidth on multiport bonded interfaces).
+
+    * - | ``ROCSHMEM_GDA_PCIE_RELAXED_ORDERING``
+        | Enables PCIe Relaxed Ordering when registering the symmetric heap with the RDMA NICs.
+      - ``0``
+      - | 0: Disabled.
+        | 1: Enabled.