From b5a24f31871d900342a3c47398cc75e22bad0b6f Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Sat, 11 Jan 2020 00:11:28 +0100
Subject: Implement SSS for OpenCL target

Sadly OpenCL kernels don't accept pointer-to-pointer arguments which
complicates the control structure implementation.

A workaround is to cast them into `uintptr_t` which is guaranteed to be large
enough to fit any pointer on the device. Special care has to be taken to always
perform the pointer shifts on actual floating point pointers and not on
type-less pointers.
---
 boltzgen/kernel/template/pattern/SSS.cl.mako       | 121 +++++++++++++++++++++
 .../template/update_sss_control_structure.cl.mako  |  21 ++++
 2 files changed, 142 insertions(+)
 create mode 100644 boltzgen/kernel/template/pattern/SSS.cl.mako
 create mode 100644 boltzgen/kernel/template/update_sss_control_structure.cl.mako

diff --git a/boltzgen/kernel/template/pattern/SSS.cl.mako b/boltzgen/kernel/template/pattern/SSS.cl.mako
new file mode 100644
index 0000000..ad5e854
--- /dev/null
+++ b/boltzgen/kernel/template/pattern/SSS.cl.mako
@@ -0,0 +1,121 @@
+<%def name="operator(name, params = None)">
+<%
+if layout.__class__.__name__ != 'SOA':
+    raise Exception('SSS pattern only works for the AOS memory layout')
+%>
+__kernel void ${name}(
+      __global uintptr_t* control
+% if 'cell_list_dispatch' in extras:
+    , __global unsigned* cells
+% else:
+    , std::size_t gid
+% endif
+% if params is not None:
+% for param_type, param_name in params:
+    , ${param_type} ${param_name}
+% endfor
+% endif
+) {
+% if 'cell_list_dispatch' in extras:
+    const unsigned int gid = cells[get_global_id(0)];
+% endif
+
+% for i, c_i in enumerate(descriptor.c):
+    __global ${float_type}* preshifted_f_${i} = ((__global ${float_type}*)control[${i}]) + ${layout.cell_preshift('gid')};
+% endfor
+
+% for i, c_i in enumerate(descriptor.c):
+    const ${float_type} f_curr_${i} = *preshifted_f_${i};
+% endfor
+
+    ${caller.body()}
+
+% for i, c_i in enumerate(descriptor.c):
+    *preshifted_f_${i} = f_next_${descriptor.c.index(-c_i)};
+% endfor
+}
+</%def>
+
+<%def name="operator_with_domain_dispatch(name, params = None)">
+__kernel void ${name}(
+      __global uintptr_t* control
+% if params is not None:
+% for param_type, param_name in params:
+    , ${param_type} ${param_name}
+% endfor
+% endif
+) {
+    const unsigned int gid = ${index.gid('get_global_id(0)', 'get_global_id(1)', 'get_global_id(2)')};
+
+% for i, c_i in enumerate(descriptor.c):
+    __global ${float_type}* preshifted_f_${i} = ((__global ${float_type}*)control[${i}]) + ${layout.cell_preshift('gid')};
+% endfor
+
+% for i, c_i in enumerate(descriptor.c):
+    const ${float_type} f_curr_${i} = *preshifted_f_${i};
+% endfor
+
+    ${caller.body()}
+
+% for i, c_i in enumerate(descriptor.c):
+    *preshifted_f_${i} = f_next_${descriptor.c.index(-c_i)};
+% endfor
+}
+</%def>
+
+<%def name="functor(name, params = None)">
+<%
+if layout.__class__.__name__ != 'SOA':
+    raise Exception('SSS pattern only works for the AOS memory layout')
+%>
+__kernel void ${name}(
+      __global const uintptr_t* control
+% if 'cell_list_dispatch' in extras:
+    , __global unsigned* cells
+% else:
+    , std::size_t gid
+% endif
+% if params is not None:
+% for param_type, param_name in params:
+    , ${param_type} ${param_name}
+% endfor
+% endif
+) {
+% if 'cell_list_dispatch' in extras:
+    const unsigned int gid = cells[get_global_id(0)];
+% endif
+
+% for i, c_i in enumerate(descriptor.c):
+    __global const ${float_type}* preshifted_f_${i} = ((__global ${float_type}*)control[${i}]) + ${layout.cell_preshift('gid')};
+% endfor
+
+% for i, c_i in enumerate(descriptor.c):
+    const ${float_type} f_curr_${i} = *preshifted_f_${descriptor.c.index(-c_i)};
+% endfor
+
+    ${caller.body()}
+}
+</%def>
+
+<%def name="functor_with_domain_dispatch(name, params = None)">
+__kernel void ${name}(
+      __global const uintptr_t* control
+% if params is not None:
+% for param_type, param_name in params:
+    , ${param_type} ${param_name}
+% endfor
+% endif
+) {
+    const unsigned int gid = ${index.gid('get_global_id(0)', 'get_global_id(1)', 'get_global_id(2)')};
+
+% for i, c_i in enumerate(descriptor.c):
+    __global const ${float_type}* preshifted_f_${i} = ((__global ${float_type}*)control[${i}]) + ${layout.cell_preshift('gid')};
+% endfor
+
+% for i, c_i in enumerate(descriptor.c):
+    const ${float_type} f_curr_${i} = *preshifted_f_${i};
+% endfor
+
+    ${caller.body()}
+}
+</%def>
diff --git a/boltzgen/kernel/template/update_sss_control_structure.cl.mako b/boltzgen/kernel/template/update_sss_control_structure.cl.mako
new file mode 100644
index 0000000..ec6a5d5
--- /dev/null
+++ b/boltzgen/kernel/template/update_sss_control_structure.cl.mako
@@ -0,0 +1,21 @@
+<%
+if streaming != 'SSS':
+    raise Exception('"update_sss_control_structure" function only makes sense for the SSS pattern')
+
+padding = (max(geometry.size_x,geometry.size_y,geometry.size_z)+1)**(descriptor.d-1)
+%>
+
+__kernel void init_sss_control_structure(__global ${float_type}* f, __global uintptr_t* control) {
+% for i, c_i in enumerate(descriptor.c):
+    control[${i}]  = (uintptr_t)(f + ${padding + layout.pop_offset(i, 2*padding)});
+% endfor
+}
+
+__kernel void update_sss_control_structure(__global uintptr_t* control) {
+% for i, c_i in enumerate(descriptor.c):
+    __global ${float_type}* f_old_${i} = (__global ${float_type}*)(control[${i}]);
+% endfor
+% for i, c_i in enumerate(descriptor.c):
+    control[${i}] = (uintptr_t)(f_old_${descriptor.c.index(-c_i)} + ${layout.neighbor_offset(-c_i)});
+% endfor
+}
-- 
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