xref: /aosp_15_r20/external/eigen/Eigen/src/Core/products/TriangularMatrixMatrix.h (revision bf2c37156dfe67e5dfebd6d394bad8b2ab5804d4)
1 // This file is part of Eigen, a lightweight C++ template library
2 // for linear algebra.
3 //
4 // Copyright (C) 2009 Gael Guennebaud <[email protected]>
5 //
6 // This Source Code Form is subject to the terms of the Mozilla
7 // Public License v. 2.0. If a copy of the MPL was not distributed
8 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
9 
10 #ifndef EIGEN_TRIANGULAR_MATRIX_MATRIX_H
11 #define EIGEN_TRIANGULAR_MATRIX_MATRIX_H
12 
13 namespace Eigen {
14 
15 namespace internal {
16 
17 // template<typename Scalar, int mr, int StorageOrder, bool Conjugate, int Mode>
18 // struct gemm_pack_lhs_triangular
19 // {
20 //   Matrix<Scalar,mr,mr,
21 //   void operator()(Scalar* blockA, const EIGEN_RESTRICT Scalar* _lhs, int lhsStride, int depth, int rows)
22 //   {
23 //     conj_if<NumTraits<Scalar>::IsComplex && Conjugate> cj;
24 //     const_blas_data_mapper<Scalar, StorageOrder> lhs(_lhs,lhsStride);
25 //     int count = 0;
26 //     const int peeled_mc = (rows/mr)*mr;
27 //     for(int i=0; i<peeled_mc; i+=mr)
28 //     {
29 //       for(int k=0; k<depth; k++)
30 //         for(int w=0; w<mr; w++)
31 //           blockA[count++] = cj(lhs(i+w, k));
32 //     }
33 //     for(int i=peeled_mc; i<rows; i++)
34 //     {
35 //       for(int k=0; k<depth; k++)
36 //         blockA[count++] = cj(lhs(i, k));
37 //     }
38 //   }
39 // };
40 
41 /* Optimized triangular matrix * matrix (_TRMM++) product built on top of
42  * the general matrix matrix product.
43  */
44 template <typename Scalar, typename Index,
45           int Mode, bool LhsIsTriangular,
46           int LhsStorageOrder, bool ConjugateLhs,
47           int RhsStorageOrder, bool ConjugateRhs,
48           int ResStorageOrder, int ResInnerStride,
49           int Version = Specialized>
50 struct product_triangular_matrix_matrix;
51 
52 template <typename Scalar, typename Index,
53           int Mode, bool LhsIsTriangular,
54           int LhsStorageOrder, bool ConjugateLhs,
55           int RhsStorageOrder, bool ConjugateRhs,
56           int ResInnerStride, int Version>
57 struct product_triangular_matrix_matrix<Scalar,Index,Mode,LhsIsTriangular,
58                                            LhsStorageOrder,ConjugateLhs,
59                                            RhsStorageOrder,ConjugateRhs,RowMajor,ResInnerStride,Version>
60 {
61   static EIGEN_STRONG_INLINE void run(
62     Index rows, Index cols, Index depth,
63     const Scalar* lhs, Index lhsStride,
64     const Scalar* rhs, Index rhsStride,
65     Scalar* res,       Index resIncr, Index resStride,
66     const Scalar& alpha, level3_blocking<Scalar,Scalar>& blocking)
67   {
68     product_triangular_matrix_matrix<Scalar, Index,
69       (Mode&(UnitDiag|ZeroDiag)) | ((Mode&Upper) ? Lower : Upper),
70       (!LhsIsTriangular),
71       RhsStorageOrder==RowMajor ? ColMajor : RowMajor,
72       ConjugateRhs,
73       LhsStorageOrder==RowMajor ? ColMajor : RowMajor,
74       ConjugateLhs,
75       ColMajor, ResInnerStride>
76       ::run(cols, rows, depth, rhs, rhsStride, lhs, lhsStride, res, resIncr, resStride, alpha, blocking);
77   }
78 };
79 
80 // implements col-major += alpha * op(triangular) * op(general)
81 template <typename Scalar, typename Index, int Mode,
82           int LhsStorageOrder, bool ConjugateLhs,
83           int RhsStorageOrder, bool ConjugateRhs,
84           int ResInnerStride, int Version>
85 struct product_triangular_matrix_matrix<Scalar,Index,Mode,true,
86                                            LhsStorageOrder,ConjugateLhs,
87                                            RhsStorageOrder,ConjugateRhs,ColMajor,ResInnerStride,Version>
88 {
89 
90   typedef gebp_traits<Scalar,Scalar> Traits;
91   enum {
92     SmallPanelWidth   = 2 * EIGEN_PLAIN_ENUM_MAX(Traits::mr,Traits::nr),
93     IsLower = (Mode&Lower) == Lower,
94     SetDiag = (Mode&(ZeroDiag|UnitDiag)) ? 0 : 1
95   };
96 
97   static EIGEN_DONT_INLINE void run(
98     Index _rows, Index _cols, Index _depth,
99     const Scalar* _lhs, Index lhsStride,
100     const Scalar* _rhs, Index rhsStride,
101     Scalar* res,        Index resIncr, Index resStride,
102     const Scalar& alpha, level3_blocking<Scalar,Scalar>& blocking);
103 };
104 
105 template <typename Scalar, typename Index, int Mode,
106           int LhsStorageOrder, bool ConjugateLhs,
107           int RhsStorageOrder, bool ConjugateRhs,
108           int ResInnerStride, int Version>
109 EIGEN_DONT_INLINE void product_triangular_matrix_matrix<Scalar,Index,Mode,true,
110                                                         LhsStorageOrder,ConjugateLhs,
111                                                         RhsStorageOrder,ConjugateRhs,ColMajor,ResInnerStride,Version>::run(
112     Index _rows, Index _cols, Index _depth,
113     const Scalar* _lhs, Index lhsStride,
114     const Scalar* _rhs, Index rhsStride,
115     Scalar* _res,       Index resIncr, Index resStride,
116     const Scalar& alpha, level3_blocking<Scalar,Scalar>& blocking)
117   {
118     // strip zeros
119     Index diagSize  = (std::min)(_rows,_depth);
120     Index rows      = IsLower ? _rows : diagSize;
121     Index depth     = IsLower ? diagSize : _depth;
122     Index cols      = _cols;
123 
124     typedef const_blas_data_mapper<Scalar, Index, LhsStorageOrder> LhsMapper;
125     typedef const_blas_data_mapper<Scalar, Index, RhsStorageOrder> RhsMapper;
126     typedef blas_data_mapper<typename Traits::ResScalar, Index, ColMajor, Unaligned, ResInnerStride> ResMapper;
127     LhsMapper lhs(_lhs,lhsStride);
128     RhsMapper rhs(_rhs,rhsStride);
129     ResMapper res(_res, resStride, resIncr);
130 
131     Index kc = blocking.kc();                   // cache block size along the K direction
132     Index mc = (std::min)(rows,blocking.mc());  // cache block size along the M direction
133     // The small panel size must not be larger than blocking size.
134     // Usually this should never be the case because SmallPanelWidth^2 is very small
135     // compared to L2 cache size, but let's be safe:
136     Index panelWidth = (std::min)(Index(SmallPanelWidth),(std::min)(kc,mc));
137 
138     std::size_t sizeA = kc*mc;
139     std::size_t sizeB = kc*cols;
140 
141     ei_declare_aligned_stack_constructed_variable(Scalar, blockA, sizeA, blocking.blockA());
142     ei_declare_aligned_stack_constructed_variable(Scalar, blockB, sizeB, blocking.blockB());
143 
144     // To work around an "error: member reference base type 'Matrix<...>
145     // (Eigen::internal::constructor_without_unaligned_array_assert (*)())' is
146     // not a structure or union" compilation error in nvcc (tested V8.0.61),
147     // create a dummy internal::constructor_without_unaligned_array_assert
148     // object to pass to the Matrix constructor.
149     internal::constructor_without_unaligned_array_assert a;
150     Matrix<Scalar,SmallPanelWidth,SmallPanelWidth,LhsStorageOrder> triangularBuffer(a);
151     triangularBuffer.setZero();
152     if((Mode&ZeroDiag)==ZeroDiag)
153       triangularBuffer.diagonal().setZero();
154     else
155       triangularBuffer.diagonal().setOnes();
156 
157     gebp_kernel<Scalar, Scalar, Index, ResMapper, Traits::mr, Traits::nr, ConjugateLhs, ConjugateRhs> gebp_kernel;
158     gemm_pack_lhs<Scalar, Index, LhsMapper, Traits::mr, Traits::LhsProgress, typename Traits::LhsPacket4Packing, LhsStorageOrder> pack_lhs;
159     gemm_pack_rhs<Scalar, Index, RhsMapper, Traits::nr,RhsStorageOrder> pack_rhs;
160 
161     for(Index k2=IsLower ? depth : 0;
162         IsLower ? k2>0 : k2<depth;
163         IsLower ? k2-=kc : k2+=kc)
164     {
165       Index actual_kc = (std::min)(IsLower ? k2 : depth-k2, kc);
166       Index actual_k2 = IsLower ? k2-actual_kc : k2;
167 
168       // align blocks with the end of the triangular part for trapezoidal lhs
169       if((!IsLower)&&(k2<rows)&&(k2+actual_kc>rows))
170       {
171         actual_kc = rows-k2;
172         k2 = k2+actual_kc-kc;
173       }
174 
175       pack_rhs(blockB, rhs.getSubMapper(actual_k2,0), actual_kc, cols);
176 
177       // the selected lhs's panel has to be split in three different parts:
178       //  1 - the part which is zero => skip it
179       //  2 - the diagonal block => special kernel
180       //  3 - the dense panel below (lower case) or above (upper case) the diagonal block => GEPP
181 
182       // the block diagonal, if any:
183       if(IsLower || actual_k2<rows)
184       {
185         // for each small vertical panels of lhs
186         for (Index k1=0; k1<actual_kc; k1+=panelWidth)
187         {
188           Index actualPanelWidth = std::min<Index>(actual_kc-k1, panelWidth);
189           Index lengthTarget = IsLower ? actual_kc-k1-actualPanelWidth : k1;
190           Index startBlock   = actual_k2+k1;
191           Index blockBOffset = k1;
192 
193           // => GEBP with the micro triangular block
194           // The trick is to pack this micro block while filling the opposite triangular part with zeros.
195           // To this end we do an extra triangular copy to a small temporary buffer
196           for (Index k=0;k<actualPanelWidth;++k)
197           {
198             if (SetDiag)
199               triangularBuffer.coeffRef(k,k) = lhs(startBlock+k,startBlock+k);
200             for (Index i=IsLower ? k+1 : 0; IsLower ? i<actualPanelWidth : i<k; ++i)
201               triangularBuffer.coeffRef(i,k) = lhs(startBlock+i,startBlock+k);
202           }
203           pack_lhs(blockA, LhsMapper(triangularBuffer.data(), triangularBuffer.outerStride()), actualPanelWidth, actualPanelWidth);
204 
205           gebp_kernel(res.getSubMapper(startBlock, 0), blockA, blockB,
206                       actualPanelWidth, actualPanelWidth, cols, alpha,
207                       actualPanelWidth, actual_kc, 0, blockBOffset);
208 
209           // GEBP with remaining micro panel
210           if (lengthTarget>0)
211           {
212             Index startTarget  = IsLower ? actual_k2+k1+actualPanelWidth : actual_k2;
213 
214             pack_lhs(blockA, lhs.getSubMapper(startTarget,startBlock), actualPanelWidth, lengthTarget);
215 
216             gebp_kernel(res.getSubMapper(startTarget, 0), blockA, blockB,
217                         lengthTarget, actualPanelWidth, cols, alpha,
218                         actualPanelWidth, actual_kc, 0, blockBOffset);
219           }
220         }
221       }
222       // the part below (lower case) or above (upper case) the diagonal => GEPP
223       {
224         Index start = IsLower ? k2 : 0;
225         Index end   = IsLower ? rows : (std::min)(actual_k2,rows);
226         for(Index i2=start; i2<end; i2+=mc)
227         {
228           const Index actual_mc = (std::min)(i2+mc,end)-i2;
229           gemm_pack_lhs<Scalar, Index, LhsMapper, Traits::mr,Traits::LhsProgress, typename Traits::LhsPacket4Packing, LhsStorageOrder,false>()
230             (blockA, lhs.getSubMapper(i2, actual_k2), actual_kc, actual_mc);
231 
232           gebp_kernel(res.getSubMapper(i2, 0), blockA, blockB, actual_mc,
233                       actual_kc, cols, alpha, -1, -1, 0, 0);
234         }
235       }
236     }
237   }
238 
239 // implements col-major += alpha * op(general) * op(triangular)
240 template <typename Scalar, typename Index, int Mode,
241           int LhsStorageOrder, bool ConjugateLhs,
242           int RhsStorageOrder, bool ConjugateRhs,
243           int ResInnerStride, int Version>
244 struct product_triangular_matrix_matrix<Scalar,Index,Mode,false,
245                                         LhsStorageOrder,ConjugateLhs,
246                                         RhsStorageOrder,ConjugateRhs,ColMajor,ResInnerStride,Version>
247 {
248   typedef gebp_traits<Scalar,Scalar> Traits;
249   enum {
250     SmallPanelWidth   = EIGEN_PLAIN_ENUM_MAX(Traits::mr,Traits::nr),
251     IsLower = (Mode&Lower) == Lower,
252     SetDiag = (Mode&(ZeroDiag|UnitDiag)) ? 0 : 1
253   };
254 
255   static EIGEN_DONT_INLINE void run(
256     Index _rows, Index _cols, Index _depth,
257     const Scalar* _lhs, Index lhsStride,
258     const Scalar* _rhs, Index rhsStride,
259     Scalar* res,        Index resIncr, Index resStride,
260     const Scalar& alpha, level3_blocking<Scalar,Scalar>& blocking);
261 };
262 
263 template <typename Scalar, typename Index, int Mode,
264           int LhsStorageOrder, bool ConjugateLhs,
265           int RhsStorageOrder, bool ConjugateRhs,
266           int ResInnerStride, int Version>
267 EIGEN_DONT_INLINE void product_triangular_matrix_matrix<Scalar,Index,Mode,false,
268                                                         LhsStorageOrder,ConjugateLhs,
269                                                         RhsStorageOrder,ConjugateRhs,ColMajor,ResInnerStride,Version>::run(
270     Index _rows, Index _cols, Index _depth,
271     const Scalar* _lhs, Index lhsStride,
272     const Scalar* _rhs, Index rhsStride,
273     Scalar* _res,       Index resIncr, Index resStride,
274     const Scalar& alpha, level3_blocking<Scalar,Scalar>& blocking)
275   {
276     const Index PacketBytes = packet_traits<Scalar>::size*sizeof(Scalar);
277     // strip zeros
278     Index diagSize  = (std::min)(_cols,_depth);
279     Index rows      = _rows;
280     Index depth     = IsLower ? _depth : diagSize;
281     Index cols      = IsLower ? diagSize : _cols;
282 
283     typedef const_blas_data_mapper<Scalar, Index, LhsStorageOrder> LhsMapper;
284     typedef const_blas_data_mapper<Scalar, Index, RhsStorageOrder> RhsMapper;
285     typedef blas_data_mapper<typename Traits::ResScalar, Index, ColMajor, Unaligned, ResInnerStride> ResMapper;
286     LhsMapper lhs(_lhs,lhsStride);
287     RhsMapper rhs(_rhs,rhsStride);
288     ResMapper res(_res, resStride, resIncr);
289 
290     Index kc = blocking.kc();                   // cache block size along the K direction
291     Index mc = (std::min)(rows,blocking.mc());  // cache block size along the M direction
292 
293     std::size_t sizeA = kc*mc;
294     std::size_t sizeB = kc*cols+EIGEN_MAX_ALIGN_BYTES/sizeof(Scalar);
295 
296     ei_declare_aligned_stack_constructed_variable(Scalar, blockA, sizeA, blocking.blockA());
297     ei_declare_aligned_stack_constructed_variable(Scalar, blockB, sizeB, blocking.blockB());
298 
299     internal::constructor_without_unaligned_array_assert a;
300     Matrix<Scalar,SmallPanelWidth,SmallPanelWidth,RhsStorageOrder> triangularBuffer(a);
301     triangularBuffer.setZero();
302     if((Mode&ZeroDiag)==ZeroDiag)
303       triangularBuffer.diagonal().setZero();
304     else
305       triangularBuffer.diagonal().setOnes();
306 
307     gebp_kernel<Scalar, Scalar, Index, ResMapper, Traits::mr, Traits::nr, ConjugateLhs, ConjugateRhs> gebp_kernel;
308     gemm_pack_lhs<Scalar, Index, LhsMapper, Traits::mr, Traits::LhsProgress, typename Traits::LhsPacket4Packing, LhsStorageOrder> pack_lhs;
309     gemm_pack_rhs<Scalar, Index, RhsMapper, Traits::nr,RhsStorageOrder> pack_rhs;
310     gemm_pack_rhs<Scalar, Index, RhsMapper, Traits::nr,RhsStorageOrder,false,true> pack_rhs_panel;
311 
312     for(Index k2=IsLower ? 0 : depth;
313         IsLower ? k2<depth  : k2>0;
314         IsLower ? k2+=kc   : k2-=kc)
315     {
316       Index actual_kc = (std::min)(IsLower ? depth-k2 : k2, kc);
317       Index actual_k2 = IsLower ? k2 : k2-actual_kc;
318 
319       // align blocks with the end of the triangular part for trapezoidal rhs
320       if(IsLower && (k2<cols) && (actual_k2+actual_kc>cols))
321       {
322         actual_kc = cols-k2;
323         k2 = actual_k2 + actual_kc - kc;
324       }
325 
326       // remaining size
327       Index rs = IsLower ? (std::min)(cols,actual_k2) : cols - k2;
328       // size of the triangular part
329       Index ts = (IsLower && actual_k2>=cols) ? 0 : actual_kc;
330 
331       Scalar* geb = blockB+ts*ts;
332       geb = geb + internal::first_aligned<PacketBytes>(geb,PacketBytes/sizeof(Scalar));
333 
334       pack_rhs(geb, rhs.getSubMapper(actual_k2,IsLower ? 0 : k2), actual_kc, rs);
335 
336       // pack the triangular part of the rhs padding the unrolled blocks with zeros
337       if(ts>0)
338       {
339         for (Index j2=0; j2<actual_kc; j2+=SmallPanelWidth)
340         {
341           Index actualPanelWidth = std::min<Index>(actual_kc-j2, SmallPanelWidth);
342           Index actual_j2 = actual_k2 + j2;
343           Index panelOffset = IsLower ? j2+actualPanelWidth : 0;
344           Index panelLength = IsLower ? actual_kc-j2-actualPanelWidth : j2;
345           // general part
346           pack_rhs_panel(blockB+j2*actual_kc,
347                          rhs.getSubMapper(actual_k2+panelOffset, actual_j2),
348                          panelLength, actualPanelWidth,
349                          actual_kc, panelOffset);
350 
351           // append the triangular part via a temporary buffer
352           for (Index j=0;j<actualPanelWidth;++j)
353           {
354             if (SetDiag)
355               triangularBuffer.coeffRef(j,j) = rhs(actual_j2+j,actual_j2+j);
356             for (Index k=IsLower ? j+1 : 0; IsLower ? k<actualPanelWidth : k<j; ++k)
357               triangularBuffer.coeffRef(k,j) = rhs(actual_j2+k,actual_j2+j);
358           }
359 
360           pack_rhs_panel(blockB+j2*actual_kc,
361                          RhsMapper(triangularBuffer.data(), triangularBuffer.outerStride()),
362                          actualPanelWidth, actualPanelWidth,
363                          actual_kc, j2);
364         }
365       }
366 
367       for (Index i2=0; i2<rows; i2+=mc)
368       {
369         const Index actual_mc = (std::min)(mc,rows-i2);
370         pack_lhs(blockA, lhs.getSubMapper(i2, actual_k2), actual_kc, actual_mc);
371 
372         // triangular kernel
373         if(ts>0)
374         {
375           for (Index j2=0; j2<actual_kc; j2+=SmallPanelWidth)
376           {
377             Index actualPanelWidth = std::min<Index>(actual_kc-j2, SmallPanelWidth);
378             Index panelLength = IsLower ? actual_kc-j2 : j2+actualPanelWidth;
379             Index blockOffset = IsLower ? j2 : 0;
380 
381             gebp_kernel(res.getSubMapper(i2, actual_k2 + j2),
382                         blockA, blockB+j2*actual_kc,
383                         actual_mc, panelLength, actualPanelWidth,
384                         alpha,
385                         actual_kc, actual_kc,  // strides
386                         blockOffset, blockOffset);// offsets
387           }
388         }
389         gebp_kernel(res.getSubMapper(i2, IsLower ? 0 : k2),
390                     blockA, geb, actual_mc, actual_kc, rs,
391                     alpha,
392                     -1, -1, 0, 0);
393       }
394     }
395   }
396 
397 /***************************************************************************
398 * Wrapper to product_triangular_matrix_matrix
399 ***************************************************************************/
400 
401 } // end namespace internal
402 
403 namespace internal {
404 template<int Mode, bool LhsIsTriangular, typename Lhs, typename Rhs>
405 struct triangular_product_impl<Mode,LhsIsTriangular,Lhs,false,Rhs,false>
406 {
407   template<typename Dest> static void run(Dest& dst, const Lhs &a_lhs, const Rhs &a_rhs, const typename Dest::Scalar& alpha)
408   {
409     typedef typename Lhs::Scalar  LhsScalar;
410     typedef typename Rhs::Scalar  RhsScalar;
411     typedef typename Dest::Scalar Scalar;
412 
413     typedef internal::blas_traits<Lhs> LhsBlasTraits;
414     typedef typename LhsBlasTraits::DirectLinearAccessType ActualLhsType;
415     typedef typename internal::remove_all<ActualLhsType>::type ActualLhsTypeCleaned;
416     typedef internal::blas_traits<Rhs> RhsBlasTraits;
417     typedef typename RhsBlasTraits::DirectLinearAccessType ActualRhsType;
418     typedef typename internal::remove_all<ActualRhsType>::type ActualRhsTypeCleaned;
419 
420     typename internal::add_const_on_value_type<ActualLhsType>::type lhs = LhsBlasTraits::extract(a_lhs);
421     typename internal::add_const_on_value_type<ActualRhsType>::type rhs = RhsBlasTraits::extract(a_rhs);
422 
423     LhsScalar lhs_alpha = LhsBlasTraits::extractScalarFactor(a_lhs);
424     RhsScalar rhs_alpha = RhsBlasTraits::extractScalarFactor(a_rhs);
425     Scalar actualAlpha = alpha * lhs_alpha * rhs_alpha;
426 
427     typedef internal::gemm_blocking_space<(Dest::Flags&RowMajorBit) ? RowMajor : ColMajor,Scalar,Scalar,
428               Lhs::MaxRowsAtCompileTime, Rhs::MaxColsAtCompileTime, Lhs::MaxColsAtCompileTime,4> BlockingType;
429 
430     enum { IsLower = (Mode&Lower) == Lower };
431     Index stripedRows  = ((!LhsIsTriangular) || (IsLower))  ? lhs.rows() : (std::min)(lhs.rows(),lhs.cols());
432     Index stripedCols  = ((LhsIsTriangular)  || (!IsLower)) ? rhs.cols() : (std::min)(rhs.cols(),rhs.rows());
433     Index stripedDepth = LhsIsTriangular ? ((!IsLower) ? lhs.cols() : (std::min)(lhs.cols(),lhs.rows()))
434                                          : ((IsLower)  ? rhs.rows() : (std::min)(rhs.rows(),rhs.cols()));
435 
436     BlockingType blocking(stripedRows, stripedCols, stripedDepth, 1, false);
437 
438     internal::product_triangular_matrix_matrix<Scalar, Index,
439       Mode, LhsIsTriangular,
440       (internal::traits<ActualLhsTypeCleaned>::Flags&RowMajorBit) ? RowMajor : ColMajor, LhsBlasTraits::NeedToConjugate,
441       (internal::traits<ActualRhsTypeCleaned>::Flags&RowMajorBit) ? RowMajor : ColMajor, RhsBlasTraits::NeedToConjugate,
442       (internal::traits<Dest          >::Flags&RowMajorBit) ? RowMajor : ColMajor, Dest::InnerStrideAtCompileTime>
443       ::run(
444         stripedRows, stripedCols, stripedDepth,   // sizes
445         &lhs.coeffRef(0,0), lhs.outerStride(),    // lhs info
446         &rhs.coeffRef(0,0), rhs.outerStride(),    // rhs info
447         &dst.coeffRef(0,0), dst.innerStride(), dst.outerStride(),    // result info
448         actualAlpha, blocking
449       );
450 
451     // Apply correction if the diagonal is unit and a scalar factor was nested:
452     if ((Mode&UnitDiag)==UnitDiag)
453     {
454       if (LhsIsTriangular && lhs_alpha!=LhsScalar(1))
455       {
456         Index diagSize = (std::min)(lhs.rows(),lhs.cols());
457         dst.topRows(diagSize) -= ((lhs_alpha-LhsScalar(1))*a_rhs).topRows(diagSize);
458       }
459       else if ((!LhsIsTriangular) && rhs_alpha!=RhsScalar(1))
460       {
461         Index diagSize = (std::min)(rhs.rows(),rhs.cols());
462         dst.leftCols(diagSize) -= (rhs_alpha-RhsScalar(1))*a_lhs.leftCols(diagSize);
463       }
464     }
465   }
466 };
467 
468 } // end namespace internal
469 
470 } // end namespace Eigen
471 
472 #endif // EIGEN_TRIANGULAR_MATRIX_MATRIX_H
473