Outer split pass for large •rand.Deal
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@ -425,6 +425,50 @@ B rand_range_c2(B t, B w, B x) {
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return taga(r);
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}
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// MergeShuffle
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static void merge_shuffle(i32* rp, i32* sp, u64 n, u64* pseed) {
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u64 seed = *pseed;
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usz log2 = 64 - CLZ(n-1);
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usz thr = 20;
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usz sh = log2<=thr? 0 : log2-thr;
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bool init = sp==NULL;
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if (init) sp = rp;
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usz i = 0; for (u64 es = n; i < n; es += n) {
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usz e = es >> sh;
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if (init) for (usz k = i; k < e; k++) rp[k] = k;
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for (; i < e; i++) {
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usz j = wy2u0k(wyrand(&seed), e-i) + i;
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usz c=sp[j]; sp[j]=sp[i]; rp[i]=c;
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}
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}
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for (; sh > 0; sh--) {
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usz i = 0;
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for (u64 es = 2*n; i < n; es += 2*n) {
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usz t = i;
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usz j = (es - n) >> sh;
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usz e = es >> sh;
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for (usz i0 = i; ; i0 += 64) {
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for (u64 r = wyrand(&seed); r; r&=r-1) {
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i = i0 + CTZ(r);
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if (i > j) { i=j; goto tail; }
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if (j == e) goto tail;
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usz c=rp[j]; rp[j]=rp[i]; rp[i]=c;
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j++;
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}
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}
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tail:
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for (; i < e; i++) {
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usz j = wy2u0k(wyrand(&seed), 1+i-t) + t;
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usz c=rp[j]; rp[j]=rp[i]; rp[i]=c;
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}
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}
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}
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*pseed = seed;
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}
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extern Arr* bitUD[3]; // from fns.c
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extern B bit2x[2];
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B rand_deal_c1(B t, B x) {
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@ -439,51 +483,61 @@ B rand_deal_c1(B t, B x) {
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if (xi == 2) {
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r = incG(bit2x[wyrand(&seed)&1]);
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} else if (LIKELY(xi <= 128)) {
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#define SHUF \
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for (usz i = 0; i < xi; i++) rp[i] = i; \
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for (usz i = 0; i < xi-1; i++) { \
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usz j = wy2u0k(wyrand(&seed), xi-i) + i; \
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usz c=rp[j]; rp[j]=rp[i]; rp[i]=c; \
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}
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i8* rp; r = m_i8arrv(&rp, xi);
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for (usz i = 0; i < xi; i++) rp[i] = i;
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for (usz i = 0; i < xi-1; i++) {
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usz j = wy2u0k(wyrand(&seed), xi-i) + i;
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usz c=rp[j]; rp[j]=rp[i]; rp[i]=c;
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}
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SHUF
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} else if (LIKELY(xi <= 1<<15)) {
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i16* rp; r = m_i16arrv(&rp, xi);
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SHUF
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#undef SHUF
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} else {
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i32* rp; r = m_i32arrv(&rp, xi);
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// MergeShuffle
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u64 n = xi;
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usz log2 = 64 - CLZ(n-1);
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usz thr = 18;
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usz sh = log2<=thr? 0 : log2-thr;
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for (u64 es = n, i = 0; i < n; es += n) {
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usz e = es >> sh;
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for (usz k = i; k < e; k++) rp[k] = k;
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for (; i < e; i++) {
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usz j = wy2u0k(wyrand(&seed), e-i) + i;
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usz c=rp[j]; rp[j]=rp[i]; rp[i]=c;
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}
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}
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for (; sh > 0; sh--) {
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if (n <= 1<<19) {
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merge_shuffle(rp, NULL, n, &seed);
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} else {
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// Initial split pass like a random radix sort
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// Don't count partition size exactly; instead, assume lengths
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// are within 1 and stop when a partition is full
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// Shuffle leftovers in at the end
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usz log2 = 64 - CLZ(n-1);
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usz thr = 16;
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usz sd = log2<thr+8? log2-thr : 8;
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usz m = 1<<sd; // Number of partitions
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u64 mm = 0x0101010101010101ull * (m-1);
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TALLOC(usz, pos, 2*m) // Current and ending positions
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pos[0] = 0; pos[2*m-1] = n;
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for (usz p=1; p<m; p++) pos[2*p-1] = pos[2*p] = (n*p) >> sd;
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usz i = 0;
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for (u64 es = 2*n; i < n; es += 2*n) {
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usz t = i;
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usz j = (es - n) >> sh;
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usz e = es >> sh;
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for (usz i0 = i; ; i0 += 64) {
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for (u64 r = wyrand(&seed); r; r&=r-1) {
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i = i0 + CTZ(r);
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if (i > j) { i=j; goto tail; }
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if (j == e) goto tail;
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usz c=rp[j]; rp[j]=rp[i]; rp[i]=c;
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j++;
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}
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}
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tail:
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for (; i < e; i++) {
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usz j = wy2u0k(wyrand(&seed), 1+i-t) + t;
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usz c=rp[j]; rp[j]=rp[i]; rp[i]=c;
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while (1) {
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u64 r = wyrand(&seed) & mm;
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for (usz j = 0; j < 8; j++) {
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u8 k = r; r>>= 8;
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usz* pp = pos+2*k;
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usz p = pp[0];
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if (p == pp[1]) goto split_done;
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pp[0]++;
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rp[p] = i++;
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}
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}
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split_done:
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for (usz p=0, j=0, s=0; p<m; p++) {
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usz l = pos[2*p] - s;
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merge_shuffle(rp+j, rp+s, l, &seed);
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s = pos[2*p+1];
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j+= l;
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}
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TFREE(pos)
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for (usz j=i; j<n; j++) rp[j] = j;
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for (; i < n; i++) {
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usz j = wy2u0k(wyrand(&seed), 1+i);
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usz c=rp[j]; rp[j]=rp[i]; rp[i]=c;
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}
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}
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}
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RAND_END;
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