Just use bit sets, not hashing, for complementary selection
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@ -323,12 +323,12 @@ B rand_subset_c2(B t, B w, B x) {
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for (u64 i = 0; i < wi; i++) rp[i] = i;
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return r;
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}
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bool invert = wi > xi/2;
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i32 wn = invert ? xi-wi : wi;
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RAND_START;
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if (wn > xi/8) {
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if (wi > xi/8) {
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// Bit set (as bytes)
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TALLOC(u8, set, xi);
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bool invert = wi > xi/2;
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i32 wn = invert ? xi-wi : wi;
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for (u64 i = 0; i < xi; i++) set[i] = 0;
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for (i32 i = xi-wn; i < xi; i++) {
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i32 j = wy2u0k(wyrand(&seed), i+1);
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@ -342,11 +342,11 @@ B rand_subset_c2(B t, B w, B x) {
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} else {
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// Sorted "hash" set
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u64 sh = 0;
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for (u64 xt=xi/4; xt>=wn; xt>>=1) sh++;
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u64 sz = ((xi-1)>>sh)+1 + wn;
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for (u64 xt=xi/4; xt>=wi; xt>>=1) sh++;
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u64 sz = ((xi-1)>>sh)+1 + wi;
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TALLOC(i32, hash, sz);
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for (u64 i = 0; i < sz; i++) hash[i] = xi;
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for (i32 i = xi-wn; i < xi; i++) {
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for (i32 i = xi-wi; i < xi; i++) {
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i32 j = wy2u0k(wyrand(&seed), i+1);
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u64 p = (u64)j >> sh;
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while (true) {
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@ -361,16 +361,7 @@ B rand_subset_c2(B t, B w, B x) {
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}
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}
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i32* rp; r = m_i32arrv(&rp, wi);
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if (!invert) {
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for (u64 i = 0; i < sz; i++) if (hash[i]!=xi) *rp++=hash[i];
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} else {
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i32 e = 0;
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for (u64 i = 0; i < sz; i++) {
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i32 f = hash[i];
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if (f!=xi) { while (e<f) *rp++=e++; e++; }
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}
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while (e<xi) *rp++=e++;
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}
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for (u64 i = 0; i < sz; i++) if (hash[i]!=xi) *rp++=hash[i];
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TFREE(hash);
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}
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RAND_END;
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