From 7c6021f7d55a81b70afb57862c58122412d9471a Mon Sep 17 00:00:00 2001
From: Chris Elrod <elrodc@gmail.com>
Date: Wed, 13 Apr 2022 19:46:24 -0400
Subject: [PATCH] for >3 loops in a group, don't permute all possible orders

---
 src/modeling/determinestrategy.jl | 87 +++++++++++--------------------
 1 file changed, 29 insertions(+), 58 deletions(-)

diff --git a/src/modeling/determinestrategy.jl b/src/modeling/determinestrategy.jl
index a2104d9dd..ce08ef3c1 100644
--- a/src/modeling/determinestrategy.jl
+++ b/src/modeling/determinestrategy.jl
@@ -277,7 +277,6 @@ function unroll_no_reductions(ls, order, vloopsym)
     end
   end
   # latency not a concern, because no depchains
-  innerloop = last(order)
   compute_l = 0.0
   rpp = 0 # register pressure proportional to unrolling
   rpc = 0 # register pressure independent of unroll factor
@@ -477,19 +476,6 @@ end
   # X[1]*u₂factor*u₁factor + X[4] + X[2] * u₂factor + X[3] * u₁factor
   X[1] + X[2] * u₂factor + X[3] * u₁factor + X[4] * u₁factor * u₂factor
 end
-# function itertilesize(X, u₁L, u₂L)
-#     cb = Inf
-#     u₁b = 1; u₂b = 1
-#     for u₁ ∈ 1:4, u₂ ∈ 1:4
-#         c = unroll_cost(X, u₁, u₂, u₁L, u₂L)
-#         if cb > c
-#             cb = c
-#             u₁b = u₁; u₂b = u₂
-#         end
-#     end
-#     u₁b, u₂b, cb
-# end
-
 function solve_unroll_iter(X, R, u₁L, u₂L, u₁range, u₂range)
   R₁, R₂, R₃, R₄ = R[1], R[2], R[3], R[4]
   RR = R₄
@@ -860,38 +846,6 @@ function isoptranslation(ls::LoopSet, op::Operation, unrollsyms::UnrollSymbols)
   end
   0, 0x00
 end
-# function maxnegativeoffset_old(ls::LoopSet, op::Operation, u::Symbol)
-#     opmref = op.ref
-#     opref = opmref.ref
-#     mno = typemin(Int)
-#     id = 0
-#     opoffs = opref.offsets
-#     for opp ∈ operations(ls)
-#         opp === op && continue
-#         oppmref = opp.ref
-#         oppref = oppmref.ref
-#         sameref(opref, oppref) || continue
-#         opinds = getindicesonly(op)
-#         oppinds = getindicesonly(opp)
-#         oppoffs = oppref.offsets
-#         # oploopi = opmref.loopedindex
-#         # opploopi = oppmref.loopedindex
-#         mnonew = typemin(Int)
-#         for i ∈ eachindex(opinds)
-#             if opinds[i] === u
-#                 mnonew = (opoffs[i] - oppoffs[i])
-#             elseif opoffs[i] != oppoffs[i]
-#                 mnonew = 1
-#                 break
-#             end
-#         end
-#         if mno < mnonew < 0
-#             mno = mnonew
-#             id = identifier(opp)
-#         end
-#     end
-#     mno, id
-# end
 function maxnegativeoffset(ls::LoopSet, op::Operation, u::Symbol)
   mno::Int = typemin(Int)
   id = 0
@@ -968,7 +922,7 @@ function load_elimination_cost_factor!(
   if !iszero(first(isoptranslation(ls, op, unrollsyms)))
     rt, lat, rp = cost(ls, op, (u₁loopsym, u₂loopsym), vloopsym, Wshift, size_T)
     # rt = Core.ifelse(isvectorized(op), 0.5rt, rt)
-    rto = rt
+    # rto = rt
     rt *= iters
     # rt *= factor1; rp *= factor2;
     choose_to_inline[] = true
@@ -1315,7 +1269,7 @@ function evaluate_cost_tile!(
     else #FIXME: hack to not go crazy
       max(zero(rp), rp - one(rp))
     end
-    rto = rt
+    # rto = rt
     rt *= iters[id]
     # @show (u₁reducesrt, u₂reducesrt), (u₁reducesrp, u₂reducesrp), rto, rt, lat, rp, op
     if isstore(op) & (!u₁reducesrt) & (!u₂reducesrt)
@@ -1425,12 +1379,28 @@ end
 #   syms = collect(Base.OneTo(num_loops(ls)))
 #   LoopOrders(syms, similar(syms))
 # end
+
+function memcost_sort!(loops::Vector{Symbol}, ls::LoopSet)
+  costs = zeros(Int, length(loops))
+  for op ∈ operations(ls)
+    if accesses_memory(op)
+      for (i,l) in enumerate(loops)
+        j = findfirst(==(l), getindices(op))
+        if j !== nothing
+          costs[i] += j
+        end
+      end
+    end
+  end
+  copyto!(loops, loops[sortperm(costs,rev=true)])
+end
+
 struct LoopOrders
   syms_nr::Vector{Symbol}
   syms_r::Vector{Symbol}
   buff::Vector{Symbol}
 end
-
+max_size_for_looporder_brute() = 2
 function outer_reduct_loopordersplit(ls::LoopSet)
   ops = operations(ls)
   nonouterreducts = Int[]
@@ -1474,6 +1444,9 @@ function LoopOrders(ls::LoopSet)
   else
     reductsyms, nonreductsyms = outer_reduct_loopordersplit(ls)
   end
+  size_thresh = max_size_for_looporder_brute()
+  length(reductsyms) > size_thresh && memcost_sort!(reductsyms, ls)
+  length(nonreductsyms) > size_thresh && memcost_sort!(nonreductsyms, ls)
   LoopOrders(nonreductsyms, reductsyms, Vector{Symbol}(undef, length(ls.loopsymbols)))
 end
 
@@ -1485,7 +1458,10 @@ function Base.iterate(lo::LoopOrders)
   nr = length(lo.syms_nr)
   r = length(lo.syms_r)
   state = zeros(Int, nr + r)
-  lo.buff, (view(state, 1:nr), view(state, 1+nr:nr+r))
+  size_thresh = max_size_for_looporder_brute()
+  nrstate = nr > size_thresh ? view(state, 1:1) : view(state, 1:nr)
+  rstate = r > size_thresh ? view(state, 1+nr:1+nr) : view(state, 1+nr:nr+r)
+  lo.buff, (nrstate, rstate)
 end
 
 function advance_state!(state)
@@ -1506,12 +1482,6 @@ function advance_state!(state)
   end
   true
 end
-function advance_state!(state, Nr)
-  state_nr = view(state, 1:Nr)
-  advance_state!(state_nr) && return true
-  fill!(state_nr, 0)
-  advance_state!(view(state, 1+Nr:length(state)))
-end
 swap!(x::AbstractVector, i::Int, j::Int) = (x[j], x[i]) = (x[i], x[j])
 function swap!(
   dest::AbstractVector{Symbol},
@@ -1528,11 +1498,12 @@ end
 function Base.iterate(lo::LoopOrders, (state_nr, state_r))
   if advance_state!(state_nr)
     swap!(nonreductview(lo), lo.syms_nr, state_nr)
-  else
-    advance_state!(state_r) || return nothing
+  elseif advance_state!(state_r)
     fill!(state_nr, 0)
     copyto!(nonreductview(lo), lo.syms_nr)
     swap!(reductview(lo), lo.syms_r, state_r)
+  else
+    return nothing
   end
   lo.buff, (state_nr, state_r)
 end