# conflictd
-This is based on the AVX512 conflict detection instruction. Internally the logic is used to detect address conflicts in multi-issue LD/ST operations. Two arrays of values are given: the indices are compared and duplicates reported in a triangular fashion. the instruction may be used for histograms (computed in parallel)
-
- input = [100, 100, 3, 100, 5, 100, 100, 3]
- conflict result = [
- 0b00000000, // Note: first element always zero
- 0b00000001, // 100 is present on #0
- 0b00000000,
- 0b00000011, // 100 is present on #0 and #1
- 0b00000000,
- 0b00001011, // 100 is present on #0, #1, #3
- 0b00011011, // .. and #4
- 0b00000100 // 3 is present on #2
- ]
-
-Pseudocode:
-
- for i in range(VL):
- for j in range(1, i):
- if src1[i] == src2[j]:
- result[j] |= 1<<i
-
-Idea 1: implement this as a Triangular Schedule, Vertical-First Mode,
- using `mfcrweird` and `cmpi`. first triangular schedule on src1,
-secpnd on src2.
-
-Idea 2: implement using outer loop on varying setvl Horizontal-First
-with `1<<r3` predicate mask for src2 as scalar, creates CR field vector, transfer into INT with mfcrweird then OR into the
-result.
+moved to [[sv/cookbook/conflictd]]
-```
- li r3, target
- li result, 0
- for i in range(target):
- setvl target
- addi r3, r3, -1 # shift 1<<r3 predicate down by one
- sv.addi/sm=1<<r3 t0, src1.v, 0 # copy src1[i]
- sv.cmpi src2.v, t0 # compare src2 vector to scalar
- sv.mfcrweird t1, cr0.v, eq # copy CR eq result bits to t1
- or result, result, t1
-```
-
-See [[sv/cr_int_predication]] for full details on the crweird instructions:
-the primary important aspect here is that a Vector of CR Field's EQ bits is
-transferred into a single GPR. The secondary important aspect is that VL
-is being adjusted in each loop, testing successively more of the input
-vector against a given scalar, each time.
-
-To investigate:
-* <https://stackoverflow.com/questions/39266476/how-to-speed-up-this-histogram-of-lut-lookups>
-* <https://stackoverflow.com/questions/39913707/how-do-the-conflict-detection-instructions-make-it-easier-to-vectorize-loops>
# iota