YaneuraOu

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YaneuraOu, (やねうら王, Yaneura King)

an USI compliant open source Shogi engine as well a in 2016 CSA registered Shogi search library by Motohiro Isozaki aka Yaneurao, written in C++, licensed under the GPL 3.0. YaneuraOu with Otafuku Lab 2019 won the WCSC29 in 2019 [1] [2], YaneuraOu was mentioned in the library column of many programs participating in the WCSC29, notably runner-up Kristallweizen, third placed Tanu-King, and 14 others.

Bitboards

9x9 Shogi Bitboards are defined as array of two quad words and similar to Apery, as conditional compiled union type with 128-bit type __m128i, explicitly taking advantage of SSE2 instructions [5]:


// Bitboard 本体クラス

struct alignas(16) Bitboard
{
##if defined (USE_SSE2)
	union
	{
		// 64bit each
		u64 p[2];

		// For handling with SSE
		// bit0 represents SQ_11, bit1 represents SQ_12,…, bit81 represents SQ_99.
		// This bit position corresponds to the Square type.
		// However, bit63 is unused. This is a hack to find the rook's advantage with one pext by leaving here.
		// Invented by the magic bitboard sect, including Apery.
		__m128i m;
	};
##else // no SSE
	u64 p[2];
##endif