"""Authored tiny CSR-like records in stdlib only; SciPy is not imported."""
import json,platform
def dense(records,shape=(3,4)):
 out=[[0]*shape[1] for _ in range(shape[0])]
 for r,c,v in records:out[r][c]+=v
 return out
def demo():
 records=[(0,1,3),(0,1,4),(0,3,0),(2,0,2)];source=dense(records);snapshot=[row[:] for row in source]
 naive=dense([(r,c,v*v) for r,c,v in records]);correct=[[v*v for v in row] for row in source]
 merged={}
 for r,c,v in records:merged[r,c]=merged.get((r,c),0)+v
 canonical_records=[(r,c,v) for (r,c),v in sorted(merged.items())]
 after=dense([(r,c,v*v) for r,c,v in canonical_records]);assert after==correct and naive[0][1]==25 and correct[0][1]==49
 add_stored=dense([(r,c,v+1) for r,c,v in canonical_records]);add_all=[[v+1 for v in row] for row in source]
 assert add_stored!=add_all and add_stored[1]==[0,0,0,0] and add_all[1]==[1,1,1,1]
 assert source==snapshot and source==[[0,7,0,0],[0,0,0,0],[2,0,0,0]]
 return {'runtime':platform.python_version(),'shape':[3,4],'raw_records':[list(x) for x in records],'csr_contract':{'data':[3,4,0,2],'indices':[1,1,3,0],'indptr':[0,3,3,4]},'dense_source':source,'canonical_records':[list(x) for x in canonical_records],'square_before_merge':naive,'square_after_merge':after,'square_dense_oracle':correct,'plus_one_stored_only':add_stored,'plus_one_dense_oracle':add_all,'f_zero':{'square':0,'plus_one':1},'scipy_executed':False,'scope':'Only12 authored cells and record-sum contract. f(0)=0 alone is insufficient before duplicate merging for nonlinear transforms; no densification advice for large data.'}
if __name__=='__main__':print(json.dumps(demo(),ensure_ascii=True,indent=2))