python - Transform 2D array to a 3D array with overlapping strides -


i convert 2d array 3d previous rows using numpy or native functions.

input:

[[1,2,3],  [4,5,6],  [7,8,9],  [10,11,12],  [13,14,15]]

output:

[[[7,8,9],    [4,5,6],    [1,2,3]],  [[10,11,12], [7,8,9],    [4,5,6]],  [[13,14,15], [10,11,12], [7,8,9]]]

any 1 can help? have searched online while, cannot got answer.

approach #1

one approach np.lib.stride_tricks.as_strided gives view input 2d array , such doesn't occupy anymore of memory space -

l = 3  # window length sliding along first axis s0,s1 = a.strides  shp = a.shape out_shp = shp[0] - l + 1, l, shp[1] strided = np.lib.stride_tricks.as_strided out = strided(a[l-1:], shape=out_shp, strides=(s0,-s0,s1))

sample input, output -

in [43]: out[43]:  array([[ 1,  2,  3],        [ 4,  5,  6],        [ 7,  8,  9],        [10, 11, 12],        [13, 14, 15]])  in [44]: out out[44]:  array([[[ 7,  8,  9],         [ 4,  5,  6],         [ 1,  2,  3]],         [[10, 11, 12],         [ 7,  8,  9],         [ 4,  5,  6]],         [[13, 14, 15],         [10, 11, 12],         [ 7,  8,  9]]])

approach #2

alternatively, bit easier 1 broadcasting upon generating of row indices -

in [56]: a[range(l-1,-1,-1) + np.arange(shp[0]-l+1)[:,none]] out[56]:  array([[[ 7,  8,  9],         [ 4,  5,  6],         [ 1,  2,  3]],         [[10, 11, 12],         [ 7,  8,  9],         [ 4,  5,  6]],         [[13, 14, 15],         [10, 11, 12],         [ 7,  8,  9]]])

Comments

Post a Comment

Popular posts from this blog

Is there a better way to structure post methods in Class Based Views -

i'm using class based views in django , never specify url in ajax calls , omit action parameter in form because know these requests go through post method of class based view. notice view - profile page make many requests depending on user updating on page - post method become convoluted , if/else mess example: def post(self, request, *args, **kwargs): # handle user changing available date if request.post.get('availabledate') != none: self.updateavailabledate(request) return jsonresponse({'result':'success'}) if request.post.get('newprojectname') != none: creative_user = creativeuserprofile.objects.get(id = request.user.id) project = project.create_project(creative_user, request.post['newprojectname']) project.save() return jsonresponse({'projectid': project.id }) if request.post.get('projectimage') != none , request.files['file']: proj
Read more

performance - Why is XCHG reg, reg a 3 micro-op instruction on modern Intel architectures? -

i'm doing micro-optimization on performance critical part of code , came across sequence of instructions (in at&t syntax): add %rax, %rbx mov %rdx, %rax mov %rbx, %rdx i thought had use case xchg allow me shave instruction , write: add %rbx, %rax xchg %rax, %rdx however, dimay found agner fog's instruction tables , xchg 3 micro-op instruction 2 cycle latency on sandy bridge, ivy bridge, broadwell, haswell , skylake. 3 whole micro-ops , 2 cycles of latency! 3 micro-ops throws off 4-1-1-1 cadence , 2 cycle latency makes worse original in best case since last 2 instructions in original might execute in parallel. now... cpu might breaking instruction micro-ops equivalent to: mov %rax, %tmp mov %rdx, %rax mov %tmp, %rdx where tmp anonymous internal register , suppose last 2 micro-ops run in parallel latency 2 cycles. given register renaming occurs on these micro-architectures, though, doesn't make sense me done way. why wouldn't register renamer
Read more

jquery - Responsive Navbar with Sub Navbar -

good day, forgive me nav vocabulary not best. if question confusing apologize. i'm working on navigation bar needs centered on page @ 768px , above. items in nav open (or perhaps toggle) subnav lives directly below. these nav should appear centered on page. i have been able work through responsive portion of nav bar, having main items align vertically , sub nav menu of each item roll out below, , gave them indent separation. working well. however, issue not responsive side, behavior @ width greater 768px. happens toggling menu's sub navigation pushes other main items down page below sub nav. here's code: $(document).ready(function () { //stick in fixed 100% height behind navbar don't wrap $('#slide-nav.navbar-inverse').after($('<div class="inverse" id="navbar-height-col"></div>')); $('#slide-nav.navbar-default').after($('<div id="navbar-height-col"></d
Read more