additional plot, and short script to do a nonvectorized benchmark (like they...

2026-06-01 10:57:34 +02:00
parent fcff5b0389
commit df4fb4a154
3 changed files with 110 additions and 2 deletions
@@ -0,0 +1,67 @@
+#!/bin/bash
+# milestone 10: find the best NON-vectorized scalar variant.
+# we compile each scalar (double, no-intrinsics) variant with vectorization
+# turned off (-fno-tree-vectorize -fno-tree-slp-vectorize) so -march=native
+# can't sneak SIMD in, then time them on a small input.
+#
+# small on purpose: N=500, 200 iters -> each build+run is a couple seconds.
+# compare T(n) [cycles] to pick the fastest. flops/cycle is printed too but
+# don't rank by it: the symmetry variants do half the work, so their
+# flops/cycle looks low even when the runtime is good.
+#
+# run from the repo root:  bash scripts/test_novec.sh
+
+set -e
+
+CXX="${CXX:-$(command -v g++ || command -v clang++)}"
+N=500
+ITER=200
+NOVEC="-fno-tree-vectorize -fno-tree-slp-vectorize"
+FLAGS="-O3 -march=native -std=c++23 -flto $NOVEC -DBENCHMARK=1 -DFLOPCOUNT=0 -DRANDOM_SEED=0 -DROOFLINE=0"
+
+# variant:main_file . symmetry variants need main-symmetry.cpp (halved flop formula),
+# everything else uses main.cpp. only double, no-AVX variants here.
+CANDIDATES=(
+  "baseline:main.cpp"
+  "inlining_7:main.cpp"
+  "inlining_8:main.cpp"
+  "cutoff:main.cpp"
+  "cutoff_callsite:main.cpp"
+  "branchless:main.cpp"
+  "branchless_sqrtfree:main.cpp"
+  "lut_exp:main.cpp"
+  "inlining_7_SoA:main.cpp"
+  "inlining_7_symmetry_2:main-symmetry.cpp"
+  "inlining_7_symmetry_2_ilp_2:main-symmetry.cpp"
+)
+
+echo "compiler: $CXX"
+echo "flags:    $FLAGS"
+echo "input:    N=$N ITER=$ITER"
+echo ""
+printf "%-34s %18s %14s\n" "variant" "cycles" "flops/cycle"
+printf "%-34s %18s %14s\n" "-------" "------" "-----------"
+
+for entry in "${CANDIDATES[@]}"; do
+  v="${entry%%:*}"
+  main="${entry##*:}"
+  src="variants/variant_${v}.cpp"
+
+  if [ ! -f "$src" ]; then
+    printf "%-34s %18s\n" "$v" "(no source, skipped)"
+    continue
+  fi
+
+  bin="novec_${v}"
+  $CXX "$main" "$src" -o "$bin" $FLAGS 2>/dev/null
+
+  out="$(./"$bin" "$N" "$ITER")"
+  cyc="$(echo "$out" | grep 'T(n):' | grep -oE '[0-9.]+')"
+  fpc="$(echo "$out" | grep 'P(n):' | grep -oE '[0-9.]+')"
+
+  printf "%-34s %18s %14s\n" "$v" "$cyc" "$fpc"
+  rm -f "$bin"
+done
+
+echo ""
+echo "lowest cycles = best non-vectorized variant. report that number for milestone 10."