lapack/testlapack: add implementation comments to Dtrtri test

lapack/testlapack/dtrtri.go

@@ -40,6 +40,7 @@ func DtrtriTest(t *testing.T, impl Dtrtrier) {
 				if lda == 0 {
 					lda = n
 				}
+				// Allocate n×n matrix A and fill it with random numbers.
 				a := make([]float64, n*lda)
 				for i := range a {
 					a[i] = rnd.Float64()
@@ -50,7 +51,9 @@ func DtrtriTest(t *testing.T, impl Dtrtrier) {
 				}
 				aCopy := make([]float64, len(a))
 				copy(aCopy, a)
+				// Compute the inverse of the uplo triangle.
 				impl.Dtrtri(uplo, diag, n, a, lda)
+				// Zero out the opposite triangle.
 				if uplo == blas.Upper {
 					for i := 1; i < n; i++ {
 						for j := 0; j < i; j++ {
@@ -67,13 +70,16 @@ func DtrtriTest(t *testing.T, impl Dtrtrier) {
 					}
 				}
 				if diag == blas.Unit {
+					// Set the diagonal explicitly to 1.
 					for i := 0; i < n; i++ {
 						a[i*lda+i] = 1
 						aCopy[i*lda+i] = 1
 					}
 				}
+				// Compute A^{-1} * A and store the result in ans.
 				ans := make([]float64, len(a))
 				bi.Dgemm(blas.NoTrans, blas.NoTrans, n, n, n, 1, a, lda, aCopy, lda, 0, ans, lda)
+				// Check that ans is the identity matrix.
 				iseye := true
 				for i := 0; i < n; i++ {
 					for j := 0; j < n; j++ {