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New skill capturing performance optimization patterns for Mojo code. Layers on top of mojo-syntax and is triggered when profiling, benchmarking, tuning latency, or porting performance-sensitive code to Mojo. Covers hot-path inlining, unsafe pointer access in inner loops, pre-allocation and lazy containers, struct layout for cache efficiency, views over owned strings, ref over var in loops, _Global lazy caches, init_pointee_move for heap fields, hash-keyed caching, comptime specialization, nibble-based SIMD byte scanning, prefiltering strategies, numeric accumulation, fast-path dispatch by input shape, and guidance on what not to optimize.
msaelices
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mojo-optimizations skill
Replace the hand-rolled perf_counter_ns harness with the stdlib std.benchmark idiom (Bench, Bencher, BenchConfig, BenchId, keep, ThroughputMeasure). Matches the pattern used in mojo/stdlib/benchmarks/ so users copy-paste from the reference tree instead of reinventing warmup and calibration logic.
…ehavior The previous text incorrectly claimed List, Span, and StringSlice all emit a bounds check on every __getitem__ call. Verified against the stdlib (std/collections/_index_normalization.mojo and std/builtin/debug_assert.mojo): List and Span both pass assert_always=False to normalize_index, so their bounds check compiles out in default (ASSERT=safe) release builds. Only StringSlice[byte=i] emits the check by default, plus a UTF-8 start-byte debug_assert. Replace the section with a per-type table of actual costs, explain what unsafe_ptr() reliably buys you in default release (negative-index branch, trap-free loop optimization, parity with -D ASSERT=all builds), and mention list.unsafe_get(idx) as a safer middle ground.
Replace the regex-specific example (CompiledRegex, _get_regex_cache, ImmSlice) with a neutral get_or_build pattern that applies to any expensive value keyed by a string. Add a brief list of use cases (parsed configs, compiled templates, resolved paths, interned symbols, SQL plans) so readers see the shape beyond regex.
Replace regex-flavored examples (CompiledRegex, DFAMatcher, Match, LazyDFA, compile_regex, match_first, is_match, .*literal) with a variety of neutral domains: - Benchmark: parse_json - Inlining trampolines: JsonParser -> Tokenizer -> ByteScanner - Struct layout: Token (tokenizer output) - Views: tokenize(source) - ref over var: rows, table - Global caches: SymbolTable, intern() - init_pointee_move: Arena - SIMD scanning: JSON whitespace, CSV delimiters, URL-safe chars - Prefilters: log scanning, filename extraction, JSON value detection - Fast-path dispatch: QueryPlan (pk lookup, sequential scan, general) - Unlikely-branch hoisting: validate(input)
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Summary
mojo-optimizationsskill capturing performance optimization patterns for Mojo. Layers on top ofmojo-syntaxand is triggered when profiling, benchmarking, tuning latency, or porting performance-sensitive code to Mojo.refovervarin loops,_Globallazy caches,init_pointee_movefor heap fields, hash-keyed caching,comptimespecialization, nibble-based SIMD byte scanning, prefiltering strategies, numeric accumulation, fast-path dispatch by input shape, and guidance on what not to optimize.README.mdwith an entry for the new skill.