Bus interaction batch lookup and permutation test (#2479)

Depends on #2474, which depends on #2465.

Added a test for new API `bus_multi_batch_lookup_permutation` per
@Schaeff's suggestion. This currently invokes the API in a raw way, so I
will add more tests in another PR that uses permutation and lookup
syntaxs in block machine to conduct integrated test of our linker
infrastructure.

pipeline/tests/powdr_std.rs

@@ -244,6 +244,14 @@ fn bus_multi_permutation() {
     test_plonky3_pipeline(pipeline);
 }
 
+#[test]
+fn bus_multi_batch_lookup_permutation() {
+    let f = "std/bus_multi_batch_lookup_permutation.asm";
+    let pipeline = make_simple_prepared_pipeline::<GoldilocksField>(f, LinkerMode::Bus);
+    test_mock_backend(pipeline.clone());
+    test_plonky3_pipeline(pipeline);
+}
+
 #[test]
 fn write_once_memory_test() {
     let f = "std/write_once_memory_test.asm";

test_data/std/bus_multi_batch_lookup_permutation.asm

@@ -0,0 +1,59 @@
+use std::protocols::bus::BusInteraction;
+use std::protocols::bus::bus_multi_send;
+use std::protocols::bus::bus_multi_receive_batch_lookup_permutation;
+
+machine Main with degree: 8 {
+    // Lookup LHS
+    col fixed x = [1, 5, 2, 6, 4, 2, 6, 3]; // input
+    col witness y; // output for x + 1
+    col witness z; // output for x + 2
+
+    let LOOKUP_ID_0 = 42;
+    let LOOKUP_ID_1 = 53;
+
+    // Lookup RHS
+    // A small block machine that precomputes:
+    // f(x) = x + 1 for all x in [1, 8]
+    // g(x) = x + 2 for all x in [1, 8]
+    col fixed LOOKUP_X = [1, 2, 3, 4, 5, 6, 7, 8];
+    col fixed LOOKUP_Y = [2, 3, 4, 5, 6, 7, 8, 9];
+    col fixed LOOKUP_Z = [3, 4, 5, 6, 7, 8, 9, 10];
+    // Note that latch for lookup RHS is provided as a constant in BusInteraction::Send
+    col fixed lookup_latch = [1]*;
+
+    // Permutation LHS
+    // Will use the same inputs x
+    col witness a; // output for x + 42
+    col witness b; // output for x + 21
+
+    col fixed sel = [1, 1, 1, 0, 0, 0, 0, 0]; // LHS call selector (link if flag ~>)
+
+    let PERMUTATION_ID_0 = 123;
+    let PERMUTATION_ID_1 = 456;
+
+    // Permutation RHS
+    // A small block machine that computes:
+    // f(x) = x + 42 for any x
+    // g(x) = x + 21 for any xs
+    col witness sub_sel_0, sub_sel_1; // RHS call selectors (block machine header `call_selectors`)
+    col witness PERM_X, PERM_A, PERM_B;
+    PERM_A = PERM_X + 42;
+    PERM_B = PERM_X + 21;
+    col fixed perm_latch = [1]*;
+
+    // Multi send (same API for both lookup and permutation)
+    bus_multi_send([
+      BusInteraction::Send(LOOKUP_ID_0, [x, y], lookup_latch), // latch is always the same as multiplicity for sends (for both lookup and permutation)
+      BusInteraction::Send(LOOKUP_ID_1, [x, z], lookup_latch),
+      BusInteraction::Send(PERMUTATION_ID_0, [x, a], sel),
+      BusInteraction::Send(PERMUTATION_ID_1, [x, b], sel)
+    ]);
+
+    // Multi receive (last argument `is_permutation` is 1 for permutation and 0 for lookup)
+    bus_multi_receive_batch_lookup_permutation([
+      (LOOKUP_ID_0, lookup_latch, [LOOKUP_X, LOOKUP_Y], 0), // selector is lookup_latch, multiplicity is a witness column (not an input here)
+      (LOOKUP_ID_1, lookup_latch, [LOOKUP_X, LOOKUP_Z], 0), // selector is lookup_latch, multiplicity is a witness column (not an input here)
+      (PERMUTATION_ID_0, sub_sel_0 * perm_latch, [PERM_X, PERM_A], 1), // selector is sub_sel_0 * perm_latch, multiplicity is selector negated
+      (PERMUTATION_ID_1, sub_sel_1 * perm_latch, [PERM_X, PERM_B], 1) // selector is sub_sel_1 * perm_latch, multiplicity is selector negated
+    ]);
+}